Claims
- 1. A process for making a high strength, high toughness magnesium alloy comprising the steps of preparing a melt comprised of magnesium and lithium metals including a total of more than 5 ppm of alkali metal impurities selected from the group consisting of sodium, potassium, rubidium and cesium; and reducing the alkali metal impurities by vacuum refining so that the total concentration of said alkali metal impurities in the alloy is less than about 5 ppm.
- 2. A process for preparing a high strength magnesium alloy comprising heating a melt comprised of a base metal of magnesium, greater than 0.5% of lithium, and at least one alkali metal impurity selected from the group consisting of sodium, potassium, rubidium and cesium, the total alkali metal present in an amount greater than 5 ppm, to a temperature of about 50.degree. to 200.degree. C. above the melting point of alloy being refined in a vacuum for a sufficient time to reduce the aggregate concentration of alkali metal impurities in the melt to less than about 5 ppm as measured by GDMS.
- 3. The process of claim 2 wherein the aggregate concentration of alkali metal impurities is reduced to less than about 3 ppm.
- 4. The process of claim 2 wherein the aggregate concentration of alkali metal impurities is reduced to less than about 1 ppm.
- 5. The process of claim 2 wherein the aggregate concentration of alkali metal impurities is reduced to less than about 0.5 ppm.
- 6. The process of claim 2 wherein the vacuum is less than about 200 .mu.m Hg and the temperature is about 50.degree. to about 100.degree. C. above the melting point of the alloy being refined.
- 7. The process of claim 2 wherein the hydrogen concentration in the melt is reduced to less than about 0.2 ppm, measured by LECO fusion technique.
- 8. The process of claim 2 wherein the hydrogen concentration in the melt is reduced to less than about 0.1 ppm, measured by LECO fusion technique.
- 9. The process of claim 2 further comprising the step of purging the melt with an inert gas.
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a divisional of U.S. application Ser. No. 08/076,117, filed Jun. 14, 1993, now U.S. Pat. No. 5,422,066, issued Jun. 6, 1995, which is a continuation-in-part of U.S. application Ser. No. 07/946,245, filed Sep. 17, 1992 (now abandoned), and a continuation-in-part of U.S. application Ser. No. 07/771,907, filed Oct. 4, 1991, now U.S. Pat. No. 5,320,803, issued Jun. 14, 1994, both of which were continuations-in-part of U.S. application Ser. No. 07/328,364, filed Mar. 24, 1989, now U.S. Pat. No. 5,085,830, issued Feb. 4, 1992. The disclosures of these applications are hereby incorporated by reference.
Foreign Referenced Citations (1)
Number |
Date |
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130985 |
Jul 1946 |
AUX |
Related Publications (1)
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771907 |
Oct 1991 |
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Divisions (1)
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76117 |
Jun 1993 |
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Continuation in Parts (3)
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946245 |
Sep 1992 |
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328364 |
Mar 1989 |
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328364 |
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