Note : Les revendications sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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