WROUGHT ALUMINUM BASE ALLOY PRODUCTS HAVING REFINED INTERMETALLIC PHASES

ARTICLES CORROYES A BASE D'ALLIAGE D'ALUMINIUM A PHASES INTERMETALLIQUES AFFINEES

English Abstract

Abstract of the Disclosure
A wrought aluminum alloy product is disclosed. The
alloy comprises 0.5 to 10 wt.% Mg, 0 to 0.35 wt.% Cr, at least
0.005 wt.% Sr, less than 1 wt.% Fe, 3.5 wt.% max. Zn, 1 wt.%
max. Cu, 0.3 wt.% max. Ti, the remainder aluminum and incidental
impurities, and wherein the alloy further comprises either: (a)
0.1 to 1.6 wt.% Mn and 1 wt.% max. Si, and the product has at
least one intermetallic phase of the type containing Al-Fe-Si,
Al-Fe-Mn and Al-Fe-Mn-Si, wherein at least one of such phases is
refined; or (b) 0.3 wt.% max. Mn and 0.3 wt.% max. free Si, and
the product has an intermetallic phase of the type containing
Al-Fe in a refined condition.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A wrought aluminum alloy product, wherein the alloy
comprises 0.5 to 10 wt.% Mg, 0 to 0.35 wt.% Cr, at least 0.005
wt.% Sr, less than 1 wt.% Fe, 3.5 wt.% max. Zn, 1 wt.% max.
Cu, 0 to 0.3 wt.% Ti, the remainder aluminum and incidental
impurities, and wherein the alloy further comprises either: (a)
0.1 to 1.8 wk.% Mn and 1 Wt.% max. Si, and the product has at
least one intermetallic phase of the type containing Al-Fe-Si,
Al-Fe-Mn and A1-Fe-Mn-Si, wherein at least one of such phases
is refined; or (b) 0.3 wt.% max. Mn and 0.3 wt.% max. free Si,
and the product has an intermetallic phase of the type contain-
ing Al-Fe in a refined condition.


2. A product according to claim 1, wherein Mg is
maintained in a range of 0.5 to 5.6 wt.%.


3. A product according to claim 2, wherein Mg is
maintained in the range of 3.5 to 4.5 wt.%.

4. A product according to claim 1, wherein the Mn of
part (a) is less than 1 wt.%.

5. A product according to claim 4, wherein the Mn of
part (a) is maintained in the range of 0.2 to 0.8 wt.%.

6. A product according to claim 1, wherein Sr is

maintained in the range of 0.01 to 0.25 wt.%.

7. A product according to claim 1, wherein the alloy
defined by part (a) comprises 0.5 to 5.6 wt.% Mg, 0.25 wt.% max.
Cr, 0.005 to 0.5 wt.% Sr, less than 0.5 wt.% Fe and 0.5 wt.%
max. Si.

8. A product according to claim 1 wherein the alloy of

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part (a) is in the form of a flat rolled or sheet product suit-
able for machining and use as a substrate.

9. A product according to claim 8, in the form of a
memory disc substrate.


10. A product according to claim 9, having a layer of
memory medium provided on said substrate.

11. A product according to claim 1, wherein the Mn of
part (b) is 0.2 wt.% max.

12. A product according to claim 2, wherein the alloy
defined by part (b) comprises 0.25 wt.% max. Cr. 0.005 to 0.5
wt.% Sr, less than 0.5 wt.% Fe, and 0.2 wt.% max. free Si.

13. A method of producing a wrought aluminum alloy
product, comprising the steps of: (1) providing a body of
aluminum base alloy as defined in claim 1, the alloy composition
being in accordance with part (a); (2) heating the body to a
temperature of not greater than 1100°F (595°C); and (3) working
said body to produce a wrought aluminum alloy product having at
least one intermetallic phase of the type containing Al-Fe-Si,
Al-Fe-Mn and Al-Fe-Mn-Si, wherein at least one of such phases is
refined.

14. A method according to claim 13, wherein in step (3)
the body is hot rolled to produce a flat rolled or sheet
product.

15. A method according to claim 14, wherein a sheet
product is produced which is suitable for machining and use as
a substrate such as a memory disc substrate.

16. A method according to claim 15, wherein for producing

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a memory disc, in step (3) said rolling is completed at a
temperature of from 400°F to 600°F (205°C to 315°C), and there
are performed the further steps of: (4) cold rolling the sheet
product to a final gauge, the sheet having at least one
intermetallic phase of the type containing Al-Fe-Si, Al-Fe-Mn
and Al-Fe-Mn-Si, wherein at least one of such phases is refined;
(5) stamping a memory disc substrate from said cold rolled
sheet; (6) machining said substrate to provide a smooth surface
thereon; and (7) depositing a layer of memory medium on said
substrate to provide the memory disc.

17. A method according to claim 16, wherein the memory
medium is comprised of a thin metallic layer.

18. A method according to claim 16, wherein the memory
medium is comprised of iron oxide suspended in a plastic carrier.

19. A method according to claim 16, wherein the body is
rolled at a temperature in the range of 600°F to 1050°F
(315°C to 565°C).

20. A method according to claim 16, wherein the body is
rolled at a temperature in the range of 750°F to 950 F (400 C to
510°C)

21. A method according to claim 13, wherein the body is
subjected to a homogenization treatment prior to said hot
rolling step, said treatment being at a temperature of 900°F
to 1100°F (482°C to 595°C) for a period of at least 1 hour.

22. A method according to claim 16, wherein the body is
hot rolled to a gauge in the range of 0.125 to 0.25 inch
(3.17 to 6.35 mm).

23. A method according to claim 16, wherein the product


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is cold rolled to a gauge in the range of 0.058 to 0.162 inch (1.47 to 4.11
mm).

24. A method according to claim 23, wherein after step (5) said sub-
strates are thermally flattened at a temperature in the range of 420°F to
750°F (215°C to 400°C) for a period of time in the range of l to 5 hours.

25. A wrought aluminum alloy product, the alloy consisting essentially
of about 2.2 to 10 wt.% Mg, 0.3 wt.% max. Mn, 0 to 0.35 wt.% Cr, 0.005 to
2.5 wt.% Sr, 0.04 to 1 wt.% Fe, 0.3 wt.% max. free Si, 3.5 wt.% max. Zn,
1 wt.% max. Cu, 0.3 wt.% max. Ti, the remainder aluminum and incidental
impurities, *he product being characterized by the presence of an inter-
metallic phase of the type containing Al-Fe in a refined condition.

26. The product in accordance with claim 25, wherein Mg is maintained
in the range of about 2.2 to 5.6 wt.%.

27. The product in accordance with claim 25, wherein Mg is maintained
in the range of 3.5 to 4.5 wt.%.

28. The product in accordance with claim 25, wherein Mn is 0.2 wt.% max.

29. The product in accordance with claim 25, wherein Fe is less than
0.5 wt.%.

30. The product in accordance with claim 25, wherein free Si is less
than 0.1 wt.%.

31. The product in accordance with claim 25, wherein Sr is maintained
in the range of 0.01 to 0.25 wt.%.

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32. A wrought aluminum alloy sheet product, the alloy
consisting essentially of about 2.2 to 5.6 wt.% Mg, 0.3 wt.%
max. Mn, 0.25 wt.% max. Cr, 0.005 to 0.5 wt.% Sr, 0.04 to 0.5
wt.% Fe, 0.3 wt.% max. Ti, 0.2 wt.% max. free Si, 3.5 wt.%
max. Zn, 1 wt.% max. Cu, the remainder aluminum and incidental
impurities, the product being characterized by the presence of
at least one intermetallic phase of the type containing Al-Fe
in a refined condition.


33. A wrought aluminum alloy product, the alloy consisting
essentially of 0.5 to 10 wt.% Mg, about 0.2 to 1.6 wt.% Mn, 0
to 0.35 wt.% Cr, 0.005 to wt.% Sr, 0.04 to 1 wt.% Fe, 1 wt.%
max. Si, 3.5 wt.% max. Zn, 1 wt.% max. Cu, 0.3 wt.% max. Ti,
the remainder aluminum and incidental impurities, the product
being characterized by the presence of at least one inter-
metallic phase of the type containing Al-Fe-Si, Al-Fe-Mn and
Al-Fe-Mn-Si, wherein at least one of such phases is refined.

34. The product in accordance with claim 34 wherein Mg
is maintained in the range of 0.5 to 5.6 wt.%.

35. The product in accordance with claim 34 wherein Mg
is maintained in the range of 3.5 to 4.5 wt.%.
36. The product in accordance with claim 34 wherein Mn
is maintained in the range of 0.2 to 0.8 wt.%.
37. The product in accordance with claim 34 wherein Mn
is less than 1 wt.%.
38. The product in accordance with claim 34 wherein Cr
is less than 0.25 wt.%.

39. The product in accordance with claim 34 wherein Fe
is less than 0.8 wt.%.

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40. The product in accordance with claim 34 wherein Fe
is less than 0.5 wt.%.

41. The product in accordance with claim 34 wherein Ti
is less than 0.3 wt.%.

42. The product in accordance with claim 34 wherein Si
is less than 0.5 wt.%.

43. The product in accordance with claim 34 wherein Si
is less than 0.35 wt.%.
44. The product in accordance with claim 34 wherein Sr
is maintained in the range of 0.005 to 0.5 wt.%.
45. The product in accordance with claim 34 wherein Sr
is maintained in the range of 0.01 to 0.25 wt.%.
46. A wrought aluminum alloy product, the alloy consisting
essentially of 0.5 to 5.6 wt.% Mg, about 0.2 to 1.8 wt.% Mn,
0.25 wt.% max. Cr, 0.005 to 0.5 wt.% Sr, 0.04 to 0.5 wt.% Fe,
0.3 wt.% max. Ti, 0.5 wt.% max. Si, 3.5 wt.% max. Zn, 1 wt.%
max. Cu, the remainder aluminum and incidental impurities,
the product being characterized by the presence of at least one
intermetallic phase of the type containing Al-Fe-Si, Al-Fe-Mn
and Al-Fe-Mn-Si, wherein at least one of such phases is refined.

47. An aluminum alloy flat rolled product, the product
consisting essentially of 0.5 to 10 wt.% Mg, about 0.2 to 1.6
wt.% Mn, 0 to 0.35 wt.% Cr, 0.005 to 0.5 wt.% Sr, 0.04 to 1 wt.%
Fe, 1 wt.% max. Si, 3.5 wt.% max. Zn, 1 wt.% max. Cu, the
remainder aluminum and incidental impurities, the product being
characterized by the presence of at least one intermetallic
phase of the type containing Al-Fe-Si, Al-Fe-Mn and Al-Fe-Mn-Si,
wherein at least one of such phases is refined.


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48. The product in accordance with claim 48 consisting
essentially of 2.2 to 5.6 wt.% Mg, 0.1 -to 1 wt.% Mn, 0 to 0.35
wt.% Cr, 0.005 to 0.5 wt.% Sr, 0.25 wt.% max. Si, 0.4 wt.% max.
Fe, 0.1 wt.% max. of both Cu and Zn, the balance aluminum and
impurities, the total of impurities not exceeding 0.15 wt.%.

49. The product in accordance with claim 48 wherein said
product is sheet.

50. A wrought aluminum alloy sheet product suitable for
machining and using as substrates, including memory disc
substrates, the product consisting of 0.5 to 10 wt.% Mg, about
0.2 to 1.4 wt.% Mn, 0 to 0.35 wt.% Cr, 0.005 to 0 wt.% Sr,
0.04 to 1 wt.% Fe, 1 wt.% max. Si, 3.5 wt.% max. Zn, 1 wt.% max.
Cu, the remainder aluminum and incidental impurities, the
product characterized by the presence of at least one inter-
metallic phase of the type containing Al-Fe-Si, Al-Fe-Mn and
Al-Fe-Mn Si, wherein one of such phases is refined.

51. The product in accordance with claim 51 wherein Mg
is in the range of 0.5 to 5.6 wt.%.

52. The product in accordance with claim 51 wherein Mg is
in the range of 3.5 to 4.5 wt.%.

53. The product in accordance with claim 51 wherein Mn
is in the range of 0.2 to 0.8 wt.%.

54. The product in accordance with claim 51 wherein Mn is
less than 1 wt.%.

55. The product in accordance with claim 51 wherein Cr is
in the range of 0.05 to 0.25 wt.%.

56. The product in accordance with claim 51 wherein Fe is
less than 0.5 wt.%.

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57. The product in accordance with claim 51 wherein Zn
is less than 0.25 wt.%.
58. The product in accordance with claim 51 wherein Ti
is less than 0.15 wt.%.
59. The product in accordance with claim 51 wherein Sr
is in the range of 0.005 to 0.5 wt.%.
60. The product in accordance with claim 51 wherein Si
is less than 0.35 wt.%.
61. A wrought aluminum alloy sheet product suitable for
machining and using as a memory disc substrate, the product
consisting essentially of 3.5 to 4.5 wt.% Mg, 0.1 to 1 wt.% Mn,
0.35 wt.% max. Cr, 0.005 to 0.5 wt.% Sr, 0.04 to 0.5 wt.% Fe,
0.35 wt.% max. Si, 0.25 wt.% max. each of Zn, Cu and Ti, the
remainder aluminum and impurities, the product characterized by
the presence of at least one intermetallic phase of the type
consisting of Al-Fe-Si, Al-Fe-Mn and Al-Fe-Mn-Si, wherein one
of such phases is refined.
62. A memory disc substrate consisting essentially of
about 3.5 to 4.5 wt.% Mg, 0.1 to 1 wt.% Mn, 0.35 wt.% max.
Cr, 0.05 to 0.5 wt.% Sr, 0.04 to 0.5 wt.% Fe, 0.35 wt.% max.
Si, 0.25 wt.% max. each of Zn, Cu and Ti, the remainder aluminum
and impurities, the product characterized by the presence of
at least one intermetallic phase of the type consisting of
Al-Fe-Si, Al-Fe-Mn and Al-Fe-Mn-Si, wherein one of such phases
is refined.

63. A memory disc comprised of an aluminum alloy substrate,
(a) the alloy consisting essentially of 0.5 to 5.6 wt.%
Mg, 1 wt.% max. Mn, 0 to 0.35 wt.% Cr, 0.005 to 0.5 wt.% Sr,
0.04 to 1 wt.% Fe and less than 1.0 wt.% Si, 3.5 wt.% max. Zn,

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the remainder aluminum and impurities, the substrate character
ized by the presence of at least one intermetallic phase of the
type containing Al-Fe-Si, Al-Fe-Mn and Al-Fe-Mn-Si, wherein
at least one of such phases is refined, and
(b) a layer of memory medium provided on said substrate.

64. The substrate in accordance with claim 64 wherein the
alloy consists essentially of 3.5 to 4.5 wt.% Mg, 0.1 to 1 wt.%
Mn, 0.35 wt.% Cr, 0.005 to 0.5 wt.% Sr, 0.5 wt.% max. Fe, 0.35
wt.% max. Si, 1 wt.% max. of both Cu and Zn, 0.25 wt.% max. Ti,
the remainder aluminum and impurities.

65. The memory medium in accordance with claim 64 wherein
the memory medium is comprised of a thin metallic layer.

66. The memory medium in accordance with claim ~ wherein
the memory medium is comprised of iron oxide suspended in a
plastic carrier.

67. The method of producing a wrought aluminum alloy
product, comprising the steps of:
(a) providing a body of aluminum base alloy consisting
essentially of 2.2 to 10 wt.% Mg, 0.1 to 1.4 wt.% Mn, 0 to 0.35
wt.% Cr, 0.005 to 0 wt.% Sr, 0.04 to 1 wt.% Fe, 1 wt.% max. Si,
3.5 wt.% max. Zn, 1 wt.% max. Cu, 0.3 wt.% max. Ti, the
remainder aluminum and incidental impurities,
(b) heating the body to a temperature of not greater
than 1100°F., and
(c) working said body to produce a wrought aluminum alloy
product being characterized by the presence of at least one
intermetallic phase of the type containing Al-Fe-Si, Al-Fe-Mn
and Al-Fe-Mn-Si, wherein at least one of such phases is refined

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68. The method in accordance with claim 68 wherein My is
maintained in the range of 2.2 to 5.6 wt.%.
69. The method in accordance with claim 68 wherein Mg is
maintained in the range of 3.5 to 4.5 wt.%.

70. The method in accordance with claim 68 wherein Mn is
maintained in the range of 0.2 to 0.8 wt.%.
71. The method in accordance with claim 68 wherein Mn is
less than 1 wt.%.
72. The method in accordance with claim 68 wherein Cr is
less than 0.25 wt.%.
73. The method in accordance with claim 68 wherein Fe is
less than 0.8 wt.%.
74. The method in accordance with claim 68 wherein Fe is
less than 0.5 wt.%.

75. The method in accordance with claim 68 wherein Ti is
less than 0.3 wt.%.

76. The method in accordance with claim 68 wherein Si is
less than 0.5 wt.%.

77. The method in accordance with claim 68 wherein Si is
less than 0.35 wt.%.

78. The method in accordance with claim 68 wherein Sr is
maintained in the range of 0.005 to 0.5 wt.%.
79. The method in accordance with claim 68 wherein Sr is
maintained in the range of 0.01 to 0.25 wt.%.

80. A method of producing a wrought aluminum alloy
product, comprising the steps of:

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(a) providing a body of aluminum base alloy consisting
essentially of 0.5 to 5.6 wt.% Mg, about 0.2 to 1.8 wt.% Mn,
0.25 wt.% max. Cr. 0.005 to 0.5 wt.% Sr, 0.04 to 0.5 wt.% Fe,
0.3 wt.% max. Ti, 0.5 wt.% max. Si, 3.5 wt.% max. Zn, 1 wt.%
max. Cu, the remainder aluminum and incidental impurities,
(b) heating the body to a temperature of not greater
than 1100°F., and
(c) working said body to produce a wrought aluminum
alloy product being characterized by the presence of at least
one intermetallic phase of the type containing Al-Fe-Si,
Al-Fe-Mn and Al-Fe-Mn-Si, wherein at least one of such phases
is refined.

81. A method of producing an aluminum alloy flat rolled
product, the method comprising the steps of:
(a) providing a body of an aluminum base alloy consisting
essentially of 0.5 to 10 wt.% Mg, about 0.2 to 1.6 wt.% Mn, 0
to 0.35 wt.% Cr, 0.005 to 0.5 wt.% Sr, 0.04 to 1 wt.% Fe, 1
wt.% max. Si, 3.5 wt.% of max. Zn, 1 wt.% max. Cu, the remainder
aluminum and incidental impurities,
(b) heating the body -to a temperature of not greater than
1100 F., and
(c) hot rolling said body to produce a flat rolled
product being characterized by the presence of at least one
intermetallic phase of the type containing Al-Fe-Si, Al-Fe-Mn
and Al-Fe-Mn-Si, wherein at least one of such phases is refined.


82. The method in accordance with claim 82 consisting
essentially of 2.2 to 5.6 wt.% Mg, 0.1 to 1 wt.% Mn, 0 to 0.35
wt.% Cr, 0.005 to 0.5 wt.% Sr, 0025 wt.% max. Si, 0.4 wt.% max.
Fe, 0.1 wt.% max. of both Cu and Zn, the balance aluminum and
impurities, the total of impurities not exceeding 0.15 wt.%.


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83. The method in accordance with claim 82 wherein said
product is sheet.

84. A method of producing a wrought aluminum alloy sheet
product suitable for machining and using as substrates,
including memory disc substrates, the method comprising the
steps of:
(a) providing a body of an aluminum base alloy consisting
of 0.5 to 10 wt.% Mg, about 0.2 to 1.4 wt.% Mn, 0 to 0.35 wt.%
Cr, 0.005 to 0 wt.% Sr, 0.04 to 1 wt.% Fe, 1 wt.% max. Si,
3.5 wt.% max. Zn, 1 wt.% max. Cu, the remainder aluminum and
incidental impurities,
(b) heating the body to a temperature of not greater
than 1100°F., and
(c) hot rolling said body to produce a wrought aluminum
alloy sheet product characterized by the presence of at least
one intermetallic phase of the type containing Al-Fe-Si,
Al-Fe-Mn and Al-Fe-Mn-Si, wherein one of such phases is refined.

85. The method in accordance with claim 85 wherein Mg
is in the range of 0.5 to 5.6 wt.%.

86. The method in accordance with claim 85 wherein Mg is
in the range of 3.5 to 4.5 wt.%.

87. The method in accordance with claim 85 wherein Mn is
in the range of 0.2 to 0.8 wt.%.

88. The method in accordance with claim 85 wherein Mn is
less than 1 wt.%.

89. The method in accordance with claim 85 wherein Cr is
in the range of 0.05 to 0.25 wt.%.

90. The method in accordance with claim 85 wherein Fe is

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less than 0.5 wt.%.
91. The method in accordance with claim 85 wherein Zn
is less than 0.25 wt.%.

92. The method in accordance with claim 85 wherein Ti is
less than 0.15 wt.%.

93. The method in accordance with claim 85 wherein Sr is
in the range of 0.005 to 0.5 wt.%.

94. The method in accordance with claim 85 wherein Si
is less than 0.35 wt.%.

95. A method of producing a wrought aluminum alloy sheet
product suitable for machining and using as memory disc
substrate, the method comprising the steps of:
(a) providing a body of an aluminum base alloy consisting
essentially of 3.5 to 4.5 wt.% Mg, 0.1 to 1 wt.% Mn, 0.35 wt.%
max. Cr, 0.005 to 0.5 wt.% Sr, 0.04 to 0.5 wt.% Fe, 0.35 wt.%
max. Si, 0.25 wt.% max. each of Zn, Cu and Ti, the remainder
aluminum and impurities,
(b) heating the body to a temperature of not greater
than 1100°F., and
(c) hot rolling said body to produce a sheet product
characterized by the presence of at least one intermetallic
phase of the type consisting of Al-Fe-Si, Al-Fe-Mn and
Al-Fe-Mn-Si, wherein one of such phases is refined.

96. A method of producing a memory disc comprised of an
aluminum alloy substrate and a layer of memory medium, the
method comprising the steps of:
(a) providing a body of an aluminum base alloy consisting
essentially of 0.5 to 5.6 wt.% Mg, 1 wt.% max. Mn, 0 to 0.35
wt.% Cr, 0.005 to 0.5 wt.% Sr, 0.04 to 1 wt.% Fe and less than

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1.0 wt.% Si, 3.5 wt.% max. Zn, the remainder aluminum and
impurities,
(b) heating the body to a temperature of not greater
than 1100°F.,
(c) rolling said body to a sheet product, with said
rolling being completed at a temperature in the range of 400°F.
to 600°F.,
(d) cold rolling the sheet product to a final gauge, the
sheet characterized by the presence of at least one intermetallic
phase of the type containing A1-Fe-Si, Al-Fe-Mn and Al-Fe-Mn-Si,
wherein at least one of such phases is reinfed,
(e) stamping a memory disc substrate from said cold
rolled sheet,
(f) machining said substrate to provide a smooth surface
thereon, said
(g) depositing a layer of memory medium on said substrate
to provide the memory disc.

97. The substrate in accordance with claim 97 wherein the
alloy consists essentially of 3.5 to 4.5 wt.% Mg, 0.1 to 1 wt.%
Mn, 0.35 wt.% Cr, 0.005 to 0.5 wt.% Sr, 0.5 wt.% max. Fe,
0.35 wt.% max. Si, 1 wt.% max. of both Cu and Zn, 0.25 wt.%
max. Ti, the remainder aluminum and impurities.

98. The memory medium in accordance with claim 97 wherein
the memory medium is comprised of a thin metallic layer.

99. The memory medium in accordance with claim 97 wherein
the memory medium is comprised of iron oxide suspended in a
plastic carrier.

100. The method in accordance with claim 97 wherein the
body is rolled at a temperature in the range of 600° F. to
1050° F.


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101. The method in accordance with claim 97 wherein the
body is rolled at a temperature in the range of 750° F. to
950° F. with said hot rolling being completed at a temperature
in the range of 400° F. to 600° F.

102. The method in accordance with claim 97 wherein the
body is subjected to a homogenization treatment prior to said
hot rolling step, said treatment being at a temperature of
900° F. to 1100° F. for a period of at least 1 hour.

103. The method in accordance with claim 97 wherein the
body is hot rolled to a gauge in the range of 0.125 to 0.25
inch.
104. The method in accordance with claim 97 wherein the
product is cold rolled to a gauge in the range of 0.058 to
0.162 inch.

105. The method in accordance with claim 97 including
thermally flattening said substrates at a temperature in the
range of 420° F. to 750° F. for a period of time in the range
of 1 to 5 hours.

106. A method of producing a memory disc having a substrate
of an aluminum base alloy and a layer of memory medium thereon,
the method comprising the steps of:
(a) providing a body of an aluminum base alloy consisting
essentially of 3.5 to 4.5 wt.% Mg. 0.1 to 1 wt.% Mn, 0.35 wt.%
max. Cr, 0.005 to 0.5 wt.% Sr, 0.04 to 0.5 wt.% Fe, 0.35 wt.%
max. Si, 0.25 wt.% max. each of Zn, Cu and Ti, the remainder
aluminum and impurities,
(b) subjecting said body to a homogenization treatment
at a temperature in the range of 900° F. to 1100° F. for a
period of at least 2 hours,


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(c) thereafter rolling said body at a temperature in the
range of 750° F. to 950° F. with said rolling being completed
at a temperature in the range of 400° F. to 600° F., said
rolling being to a gauge in the range of 0.125 to 0.25 inch,
(d) cold rolling the hot rolled product to a sheet
product having a gauge in the range of 0.058 to 0.162 inch,
(e) stamping memory disc substrates from said sheet
product and subjecting the substrate to a thermal flattening
treatment at a temperature in the range of 425° F. to 750°F.
for a period of 1 to 5 hours,
(f) machining the substrate to a smooth surface, and
(g) after cleaning the surface of the substrate,
providing a layer of memory medium thereon.

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Description

This inven-tlon relates to aluminum alloys and more
particularly it relates to ~rouyht aluminum alloy products such
as sheet products suitable for forming in-to substrates Eor
memory discs, for example.
In the fabrication of aluminum alloy substrates Eor
memory discs, normally the substrates are machined usually on
both sides prior to applying a coating thereto which functions
as memory medium. It will be appreciated that for use as a
mernory disc substrate, the surface has to be extremely smooth in
order not to interfere with the coatings and for storage of
information therein. Normally information is stored in such
coating by electrical impulses or magnetized spots where
presence or absence of such represent data and accordingly, it
will be seen that irregularities in the surface can interfere
with the ability of the coating to retain data accurately. The
machining step referred to has not been without problems. For
example, in some of the alloys used, insoluble constituents have
presented problems from a machining standpoint, resulting in a
high rejection rate for the substrates. That is, it has been
found that in certain aluminum base alloys, insoluble
constituents such as Al-Fe-Mn-Si constituents or phases, form in
rather large particle sizes, sometimes greater than 1 m, and
interfere with with the machining operation, particularly tha-t
required in the preparation of substrates for memory discs.
These constituents can in-terfere with the machining operation by
catching on the cutting tool and being removed therewith or
being pulled across the machined surface leaving scratches. In
either case, it adversely affects the smoothness desired.
Further, it is believed that when a machined surface is etched,
the large constituents interfere with uniformity of etching.
Even if the surface has been found to machine
adequately, there can be ins-tances where the coating or


undercoatlng therefor is interfered with to an extent which
affects storage of data in the coating. The interference is
believed to result from relatively large int-rme-tallic phases or
constituents as noted above. Thus, it can be seen that such
phases or constituents must be provided in a refined or modified
condition which provides freedom from such conditions.
In addition, it has been found that such or similar
problems can arise when aluminum-based alloys are anodized for
use as bright trim on automobiles. Tha-t is, -these in-termetallic
constituents can resist e-tching and anodization treatments
resulting in holes or unanodized spots in -the protec-tive anodic
coating which, of course, can severely interfere with the useful
service life of the trim. Thus, again, it can be seen -that it
is very important to provide the intermetallic phases or
insoluble constituents in a refined or modified condition which
avoids these problems. Similarly, with fine wire forming, such
as a screen wire, the large particles interfere with the forming
operation. That is, the large par-ticles can cause severe
breakage problems in wire drawing. It will be understood that
the problems referred to are used more for illustrative purposes
and that there are many other applications where relatively
large particle constituents interfere with the use of the
particular aluminum alloy.
The present invention provides an aluminum base alloy
wrought product having a refined or modified intermetallic phase
or insoluble constituent which may be machined -to a smoo-thness
suitable for use as memory disc substrates, for example. In
addition, aluminum base alloy products, e.g. extrusion or
sheet-type products, in accordance with the invention have,
inter alia, enhanced anodizing characteristics.
According to the invention there is provided a wrought
aluminum alloy produc-t, wherein the alloy comprises 0.5 to 10



- 2 -



wt.% Mg, 0 to 0.35 wt.% Cr, at least 0.005 wt.% Sr, less than
1 wt.% Fe, 3.5 wt.% ma~, ~n, 1 wt.~ max. Cu, 0 -to 0.3 wt.% Ti,
the remainder aluminum and incidental impuri-ties, and wherein
the alloy further comprises either: ~a~ 0.1 to 1.8 wt.% Mn
and 1 wt.% max. Si, and the product has at least one intermetal-
lic phase of the type containing Al-Fe Si, Al-Fe-Mn and Al-Fe-
Mn-Si, wherein at least one of such phases is refined; or (b)
0.3 wt.% max. Mn and 0.3 wt.% max. :Eree Si, and the product
has an intermetallic phase of the type containing Al-Fe in a
refined condition.
Also provided according to the invention is a method
of producing a wrought aluminum alloy product, comprising the
steps of (1) providing a body of aluminum base alloy as
defined above in accordance with part (a); (2) heating the
body to a temperature of not greater than 1100F (595C); and
(3) working said body to produce a wrought aluminum alloy
product having at least one intermetallic phase of the type
containing Al-Fe-Si, Al-Fe-Mn and Al-Fe-Mn-Si, wherein at
least one of such phases is refined.
In the accompanying drawings:
Figure 1 is a photomicrograph (500X) of an aluminum
base alloy sheet product showing constituent particles of
Al-Fe-Mn-Si which interfere with machinability of the sheet.
Figure 2 is a photomicrograph (500X) of an aluminum
base alloy sheet product of Figure 1 having refined or modified
constituent particles, the sheet product having improved




' - 3 -



machining characteris-tics and beiny particularly suitable for
memory disc substrates.
Figure 3 is a photomicrograph (500X) of the aluminum
base alloy of Figure 2, except the sheet product is provided in
a thinner gauge.
Figure 4 is a phase diagram showing the relationship
of intermetallic phases and composi-tions of an aluminum base
alloy containing 0.2 wt.% Fe after a soak period at 950F
(510C).
In certain aluminum base alloys, because of advances
in the technology in which the alloy is used, it has become
necessary to refine the constituent particle size in order to
permit use of the new technology. For example, in disc-storage
technology, efforts have been made to increase the amount of
data which can be stored on a single disc and to switch the
medium traditionally used for storage purposes in order to
circumvent problems. Efforts have been made to switch from iron
oxide-type memory medium in order to increase the medium's
resistance to erasure. Thin surface layers of cobalt, for
example, have been investigated quite successfully to determine
its suitability for such applications. ~pplications of a layer
of memory medium such as iron oxide to an aluminum substrate
involve different technology and thicker layers than that used
for applying the thin layer of cobalt, for example. For
instance, the iron oxide medium is applied to the substrate as a
slurry or dispersed in a plastic binder, whereas plating or
other forms of deposition, e.g. vapor or vacuum deposition, can
be used for applying thin, meta:Llic layers such as the thin
cobalt layers. In addition, the thin metal films are very
sensitive to defects on the surface of the aluminum substrate to
which it is applied. For example, large constituen-t particles

can interfere with the plating or deposition of the thin




metallic layer. Also, as noted earlier, the larye par-ticles can
interfere with -the smoothness of the finish at-tainable on the
aluminum substrate by machining, which in turn, is reflected in
roughness of the thin metallic film deposited on the substrate.
It must be remembexed that particles, e.g. dust particles of
about 0.3 ~ m, can in-terfere wi-th the effectiveness of the head
used for storing or reading data from the medium layer,
particularly where the medium layer is comprised of a thin
metallic layer. Accordingly, it can be seen why it is so
important to minimize roughness on the surface of the aluminum
substrate on which the layer is deposited.
Similarly, such problems with large constituen-t
particles can be encountered in anodization of aluminum alloys
used for auto trim, for example. That is, the constituent
particle on or near the surface can react or oxidize quite
differently from surrounding material resulting in defects in
the anodic coating. Such defects can adversely affect the
corrosion resistance o:E the anodic coating on the trim. Thus,

in the two examples given, it can be seen that such particles
are best avoided.

Figure 1 is a photomicrograph of an aluminum base
alloy which had been used for memory disc substrates where the
memory layer consisted particularly of iron oxide applied by the
slurry. In the micrographs, the distance between the vertical
lines corresponds to or represents 1 ~ m in the alloy
microstructure The alloy contains 0.20 wt.% Fe, 0.11 wt.% Si,
0.37 wt.% Mn, 4.06 wt.% Mg, 0.02 wt.% Cu, 0.08 wt.% Cr, 0.02
wt.% Zn and 0.01 wt.% Ti, the remainder aluminum and impurities.
However, as can be seen from the micrograph, rather large
Al-Fe-Mn-Si consti-tuent particles occur throughout the metal.
Some of the particles are on the order of about 1 ~ m which, as


'7
noted earlier, can in-terfere with machininy and conse~uently
with the memory medium.
Figure 2 shows a photomicrograph of a wrought aluminum
sheet product, particularly suitable for memory disc substrates,
in accordance with the invention. The alloy of Figure 2
contains 0.22 wt.% Fe, 0.18 wt.% Si, 0.40 w-t.% Mn, 3.85 wt.% Mg,
0.08 wt.% Cr, 0.033 wt.% Sr, 0.02 wt.% Zn, 0.03 wt.% Cu and 0.01
wt.% Ti, the remainder aluminum and incidental impurities.
Inspection of the micrograph reveals the absence of constituent
particles havi.ng a size compared to that shown in Figure 1. It
is the freedom from relatively large particles which interfere
with machining that provides the wrought sheet product shown in
Figure 2 with superior characteristics. Also, it is -the absence
of large particles which makes the product highly suitable for
substrates such as those used in memory discs, particularly
where the memory medium is a thin layer or film of metallic
material which ls plated or deposited on the substrate.
Further, in compositions or alloys in accordance with the
invention, the absence of such large particles makes the
extrusion product, e.g. auto trim, as well as sheet product
particularly suitable for anodizing. The sheet products of
Figures 1 and 2 were rolled to 0.162 inch (4.11 mm) gauge.
However, even when the sheet product of Figure 2 is rolled to a
sheet thickness of 0.082 inch (2.08 mm) gauye, it still retains
its refined or modified structure, as can be seen by examination
of the photomicrograph of Figure 3.
When a wrought product in accordance with an
embodiment of the invention is desired, the alloy can consist
essentially of 0.5 to 9 wt.% Mg, 0.1 to 1.4 wt.% Mn, 0 to 0.35
wt.% Cr/ 0.005 to 2.5 wt.% Sr, less than 1 wt.% Fe, 1 wt.% max.
Si, 3.5 wt.% max. ~n, 1 wt.% max. Cu, the remainder aluminum and
incidental impurities.


Maynesium is added or provided in -this class of
aluminum alloys rnainly for purposes of strength and is
preferably maintained in the range of 0.5 to 5~6 wt.%.
~agnesium is also useful since it promotes fine aluminum grain
size in the alloy which, of course, aids formability. It should
be noted, though, that higher levels of magnesium can lead to
fabrication problems. Thus, it becomes important to balance the
strengths desired against problems in fabrication. With respect
to machining, the higher levels of magnesium in solid solution
favor machinability. Aluminum alloys having the poorest
machining characteristics have a low alloy content and are
usually in the annealed or softest condition. Conversely,
increasing alloy concentration, cold work, solution and aging
treatments, result in an improved surface finish by hardening
the alloy, by reducing adherence of metal to the tools and by
reducing the number of burrs. That is, these additions or
treatments improve machinability. Thus, for purposes of
machining aluminum alloy substrates for memory discs, i-t is
desirable to maintain the magnesium in the range of about 3.5 to
5.5 wt.~. Where the application is aluminum screen wire, which
is drawn to a very fine diameter, maynesium should be in the
range of 4.5 to 5.6 wt.%, and where the application is aluminum
easy-open-ends for beverage containers and the like, magnesium
should be in the range of 4 to 5 wt.%. While higher levels of
magnesium have been referred to for purposes of exemplification,
lower levels of magnesium are also important in certain
applications such as alloys used for rigid containers, auto
trim, architectural products, trucks and railroad vehicles and

are contemplated to be within the purview of the invention.

With respect to manganese, it can range up to 1.4, 1.
or 1.8 wt.% but preferably it is maintained to less than 1 wt.%,

and typically it is maintained in the range of 0.1 or 0.2 to 0.8


wt.~. Manganese ls a dispersoid forming element. That is,
manganese is an element whlch is precipitated in small particle
form by thermal treatments and has, as one of its benefits, a
strengthening effect. Manganese can form dispersoid consisting
of Al-Mn, Al-Fe-Mn and Al-Fe-Mn-Si. Thus, in some
magnesium-containing alloys where it is desired to increase
corrosion resistance, magnesium can be lowered and manganese
added at no loss in strength, but with increased resistance to
corrosion. Likewise, chromium can have the advantage of
increasing corrosion resistance, particularly stress corrosion.
Also, chromium can combine with manganese to provide more
dispersoid which, as noted earlier, can increase strength.
Chrornium can also have an effect by influencing preferred
orientation with respect to earing, in cups for example. It
will be understood that earing is detrimental because it results
in wastage of metal. Preferably, chromium should not exceed
0.25 wt.% for most of the applications for which alloys of the
invention may be used.
Solid solubility of iron in aluminum is very low and
is on the order of about 0.04 to 0.05 wt.~ in ingot. Thus,
normally a large part of the iron present is usually found in
aluminum alloys as insoluble constituent in combination with
other elements such as manganese and silicon, for example.
Typical of such combinations are Al-Fe-Mn, Al-Fe-Si and
Al-Fe-Mn-Si. It will be appreciated that -the elements in these
combinations can be present in various stoichiometric amounts.
For example, Al-Fe-Si can be present as A112Fe3Si and AlgFe2Si2
which are considered to be the most commonly occurring phases.
Also, Al-Fe-Mn can be present as A16(FexMnl x~' where x is a
number greater than 0 and less than 1. With respect to
Al-Fe-Mn-Si, this combination can be present as
A112(FexMnl x)3Si, where x is a number greater than 0 and less


-than 1. It shoulcl be noted that these constl-tuen-ts are
considered to be the most common intermetallic phases found in
these types of alloys. However, it should be understood -that
other elements such as Cu, Ti and Cr and the like can appear in
or enter into the intermetallic phases referred to in minor
amounts by substituting usually for part of the Fe or Mn. Such
intermetallic phases are also contemplated within -the purview of
the invention. These insoluble constituents tend to agglomerate
and form relatively large particles such as Al-Fe-Mn-Si
constituents, as may be seen in Figure 1, some of which are
approximately 1 ~ m in length. As noted earlier, it is these
larger, insoluble constituents that are so undesirable from the
standpoint of machinability and formability. However, it must
be remembered that iron has a beneficial effect as a grain
refiner which, of course, aids machinability and formability.
Further, it must be understood that iron is normally present in
most aluminum alloys, mainly from an economic standpoint. That
is, processing aluminum to remove iron for most applications is
normally not economically feasible. Thus, many attempts have
been made to work with iron in the alloying by taking advantage
of its benefits and neutralizing its disadvantages often with
only limited success. Thus, preferably, for purposes of the
present invention, iron is maintained at 0.8 wt.% or lower, and
typically less than 0.5 wt.%, with amounts of 0.4 wt.% or less
being quite suitable.
Titanium also aids in grain refining and should be
maintained to not more -than 0.2 wt.%.
For purposes of the present invention, it is believed

that the amount of silicon also should be minimized since, at

relatively low levels it can combine with magnesium, resulting
in significant strength reductions. Thus, preferably, silicon


_ g _

should be maintained at less than 0.5 wt.% and typically less
than 0~35 wt.%.
Strontium, which should be considered to be a
character-forming element, is also an important component in the
alloys of the presen-t inven-tion. S-trontium must not be less
than 0.005 wt.% and preferably is maintained in the range of
0.005 wt.~ to 0.5 wt.% with additional amounts not presently
believed to affect the performance of the produc-ts adversely,
except that increased amounts may not be desirable from an
economic standpoint. For most applications for which alloys of
the present invention may be used, strontium is pre:Eerably
present in the range of 0.01 wt.% to 0.25 wt.%, with typical
amounts being in the range of 0.01 wt.% to 0.1 wt.%.
The addition of strontium to the composition has the
effect of refining or modifying intermetallic phases or
insoluble constituents of the type containing Al-Fe-Si, Al-Fe Mn
and Al-Fe-Mn-Si, as noted earlier. Because of the complex
nature of these phases, it is not clearly known how this effect
comes about. That is, because of the multiplicity of alloying
elements and the interaction with each other, it is indeed ~uite
surprising that significant refinement of insoluble constituent
is obtained.
However, the benefit of adding strontium can be
clearly seen by comparing the micrographs of wrought sheet
products shown in Figures 1, 2 or 3. The compositions for these
sheet products were provided hereinabove. The ingot from which
these sheet products were rolled was cast by the direct chill
method. An ingot having this composition was first scalped,
homogenized for 2 hours at 1050F (565C), and then, starting at
about a temperature of 950F (510C), hot rolled to a thickness
of about 0.182 inch (4.62 mm). From an examination of Figure 1,
it will be seen that some of the Al-Fe-Mn-Si particles or



-- 10 --

insoluble constituen-ts are relatively large and have lengths of
about 1 ~ m~ Figure 2 is a micrograph (500X) of an alloy haviny
the same composition as that shown in Figure 1 except 0.02 wt.%
strontlum was added. The alloy was rolled in the same way as
for the alloy of Figure 1. It will be seen that -the A1-Fe-Mn-Si
particles are greatly reduced in size when compared to Figure 1.
Also, the insoluble constituents including the dispersoid phase
have a substantially uniform distribution throughout the matrix.
Thus, it will be observed tha-t the s-tron-tium has the effect of
refining the intermetallic phases.
Even if the sheet product of Figure 2 is further cold
rolled to 0.082 inch (2.08 mm) gauge after annealing, the small
insoluble constituent or intermetallic phases are maintained.
For example, Figure 3 is a micrograph (500X) of an aluminum base
alloy having the same composition and fabricated in -the same way
as Figure 2, except that it was rolled to 0.082 inch (2.08 mm)
gauge. As will be observed from Figure 3, -the fine particle
constituent was maintained. Thus, from these micrographs it
will be seen that strontium has the effect of refining these
intermetallic phases in the alloy and maintaining the refined
condition after the alloy has been fabricated into a wrought
sheet product, for example.
An x-ray diffraction analysis using a Guinier-type
camera of the sheet samples referred to in Figures 1, 2 and 3
shows the relative amounts of the intermetallic phases present.
The results of the analysis are tabulated in the following
Table.


'7


~1 Q
-~1 a) I I
U~ O I I
~ U~ ~
h O h
~) ~

~ r-i
~'C h ~d I I
a~ a) ~1
FLI ~ m


._ I ~n
r~i O


ri
U~
~_ ~J
r~
1 h ~ ~
~i~1 I u~ U)
~q~
~ ~ :~
E~' ~ S~
r-i ~ :~


.,_
U~

r~
--I r-l ri ~ rl
~1) t~
U~
r-1


rl r~i ~I r-l
U~ ~I r-i r-l
V~

4~ ~1 4~
O O O
-1 t`l
~ ~ :~
O O ' O -
r-i ~) ~ ~ r~
r-i rl ~1 rl r-i -r~l

-- 12 --



As well as providiny the wrought pro~uc-t in
compositions haviny controlled amounts of alloyiny elements as
described above, it is preferred that comp~si-tions be prepared
and fabricated into products according to speciEic method steps
in order to provide the most desirable characteris-tics. Thus,
the alloys described herein can be provided as an ingot or
billet or can be strip cast for fabrication into a suitable
wrought product by techniques curren-tly employed in the art.
The cast material, such as the ingot, may be preliminarily
worked or shaped to provide suitable stock for subsequent
working operations. In certain instances, prior to the
principal working operation, the alloy stock may be subjected to
homogenization treatment and preferably at metal temperatures in
the range of 800F to 1100F (425C to 595C) for a time period
of at least 1 hour to dissolve magnesium or o-ther soluble
elements and to homogenize the internal structure of the metal
and in some cases to precipitate dispersoids. A preferred time
period is 2 hours or more at the homogenization temperature.
Normally, for ingot the heatup and homogenizing treatment do not
have to extend for more than 24 hours; however, longer times are
not normally detrimental. A soak time of 1 to 12 hours a-t the
homogenizatio~ temperature has been found quite suitable.
After the homogenizing treatment, the metal can be
rolled or extruded or otherwise subjected to working operations
to produce sto~k such as plate, sheet, extrusion or wire or
other stock suitable for shaping into the end product. To
produce a sheet-type product, a body of the alloy is preferably
hot rolled to a thickness in the range of about 0.125 to 0.25

inch (3.17 to 6.35 mm). For hot rolling purposes, the

temperature should be in the range of 600F to about 1050F
(315C to about 565C) and preferably the temperature initially
is in the range of 850F to 950F (455C to 510C)~ The

temperature at comple-tion is preferably 400F -to 600F (205C -to
315C)
When the in~ended use of a selected composition is a
typical wrought sheet product such as is suitable for memory
disc substrates, for example, final reduction as by cold rolling
can be provided. Such reduction can be -to sheet thicknesses in
the range of 0.058 to 0.162 inch (1.47 to 4.11 mm). The disc
substrates may then be stamped from the sheet and thermally
flattened at a temperature in the range of 350F to 750F (175C
10 to 400C) for a period of time of 1 to 5 hours with a typical
flattening treatment being 3 to 4 hours at 425F to 650F (220C
to 345C) under pressure. The substrates are usually rough cut
and then precision machined to remove about 0.006 inch (0.15 mm)
in order to obtain the proper degree of flatness and smoothness
before applying the memory medium. After machining, it may be
desirable to thermally flatten the substrates again. In
additlon, after machining, normally the substrates should be
degreased and given a light etching treatment. Prior to
applying the memory medium, the substrates may be given a
20 chemical conversion treatment, particularly if the iron
oxide-type memory medium is used.
In certain applications, depending on the properties
required, it may be desirable to subject the product after
working to a thermal treatment. This treatment may be provided
as an intermediate anneal or after the product has been worked
to final dimensions. For a partial anneal, the temperature is
usually in the range of 200F to 500F (95C to 260C) with a
typical range being about 300F to 500F (150C to 260C) for
time periods in the range of about 1 to 4 hours. For full
30 anneal, generally the temperature is in the range of 600F to
775F (315C to 415C) for most applications with typical
annealing practices normally being in the range of 650F to



- 14 -



750F (345C to 400C~. For full anneal, time at annealing
temperature is in the range of 1 -to 2 hours for batch ma-terial.
When the intended use of the wrought product in
accordance with the invention is screen wire, for example,
preferably the alloy consists essentially of 4 to 5~6 w-t.% Mg
0.05 to 0~2 wt.% Mn, 0.05 to 0.2 wt.% Cr, not less than 0.005
wt.% Sr, 0.4 wt.% max. Si, 0~4 wt.% max. Fe, 0.1 wt.% max. Cr,
0.25 wt.% max. Zn, the remainder aluminum and incidental
impurities. Additional impurities should not constitute more
10 than 0.15 wt.% total. When the intended use of the wrought
sheet product is truck body panels and the like, for example,
the alloy can consist essentially of 2.2 -to 2.8 wt.% Mg, 0.1
wt.% max. ~n, 0.15 to 0.35 w-t.% Cr, 0.005 to 0.25 wt.% Sr, 0.25
wt.% max. Si, 0.4 wt.% max. Fe, 0.1 wt.% max. of both Cu and Zn,
the balance aluminum and impurities, the total of impurities not
exceeding 0.15 wt.%. In instances where higher strengths may be
required, such as in tank cars and the like, while maintaining
weldability and formability, manganese may be increased in the
latter alloy to be in the range of 0.5 to 1 wt.%. Likewise,
20 where high degrees of strength are required, such as in armor
plate or in liquefied natural gas containers, magnesium can be
increased to be in the range of 4 to 4.9 wt.%.
In another aspect of the invention, it may be
desirable to control the amount of manganese in the alloy
composition in accordance with the invention to not greater -than
0.3 wt.% and preferably not greater than 0.2 wt.%. This may be
desirable where the sheet product is to be used for
easy-open-ends, for example. The phase diagram of Figure 4
shows the relationship of compositions and phases when manganese
is in the range of 0 to 0.3 wt.% and free silicon is less than
0.3 wt.% in aluminum base alloy compositions having 0.2 wt.% Fe.

In the phase diagram, the area referred to as 1 denotes that the


'Jl~.'7

only intermetallic phase obtained is the Al-Fe t~pe phase such
as FeA13 or the metastable phase Fe~16. Similarly, in -the area
denoted as 2, the interme-tallic phases of the Al-Fe and Al-Fe-Mn
[e.g. (FeMn)A16)] are obtained. The following tabulation
identifies the interme-tallic compounds found in the different
areas of the phase diagram:
Area Intermetallic Compounds
l FeAl3

2 FeA13 + (FeMn)A16
3 3 ( ) 6 12( )3

4 (FeMn)A16
(FeMn)A16 + A112(FeMn)3Si
6 FeAl3 + A~12(FeMn)3
7 All2(FeMn)3Si
8 All2(FeMn)3Si + A1l2(MnFe)3Si
9 All2(FeMn)3Si + A1l2(MnFe)3Si ~ (FeMn)A16
The addition of strontium in the composition can have the effect
of refining or modifying the Al-Fe phase when the composition
with respect to Mn and free Si is maintained within these
limits. By free Si is meant that in Mg-containing aluminum
alloys, the silicon is not combined or tied up wi-th Mg.
However, such Si may be combined with Mn, Fe, or both. With
respect to the phase diagram, it will be noted that no Mg is
present since its effect would be to lower the free silicon
content.
The phase diagram was developed as follows. A series
of alloys was prepared containing refined aluminum with 0.2% Fe.
Mn was added to provide 0.1, 0.2, 0.3 and 0.5 wt.% and Si was


added to provide from 0 to 1 wt~%. Master alloys with 0% Si and

1% Si were made as 2500 gram charges cast as notch bar.
Intermediate Si contents were made by combining the mas-ter
alloys. 200 gram charges were melted and cast as 1/4 x 2 x 4

- 16


inch (6035 x 50.8 x 101 mm) ingots in molds preheated at 600E'
(315C). The ingots were cut into 1 inch (25.4 mm) squares for
preheat experiments~ They were programmed 50F/hr (28C/hr) to
850F (455C), 950F (510C), 1050F (565C) or 1125F (605C),
held 16 hours at temperature and quenched -to retain phases
present at the preheat temperature. Phases were identified in
the specimens by x-ray diffraction and the results were used to
construct the phase diagram.
The phase diagram shows tha-t ~l-Fe--type interme-tallic
10 is the primary intermetallic phase present in the area denoted
as 1 and that this phase is also present in the areas denoted as
2, 3 and 6.
Various modifications may be made in the invention
without departing from the spirit thereof, or the scope of the
claims, and therefore, the exact form shown is to be taken as
illustrative only and not in a limiting sense, and it is desired
that only such limitations shall be placed thereon as are
imposed by the prior art, or are specifically set forth in the
appended claims.