Isostatic compression technique for powder metallurgy
AssigneeKaiser Aluminum & Chemical Corporation
InventorSteven W. Ping
Life of this patent
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Abstract
Powder metallurgy products of high tensile strength are formed in a pore-free state by a novel process which entirely avoids the use of canisters. An open-pore specimen is purged with depurative gas, backfilled with a reactive gas and, while still immersed in the reactive gas, compressed isostatically to an extent necessary to close the pores. The specimen may then be compressed to full density without the need for either high vacuum or a depurative or reactive gas atmosphere.
Claims22
A method of preparing a metal alloy product from a pre-alloyed powder which comprises:
- (a) reducing the pressure of the atmosphere surrounding a specimen comprising said powder or a porous compact thereof having substantially fully interconnecting pores and purging said specimen with a substantially dry gas, while heating said specimen to volatilize bound species from said specimen;
- (b) immersing said specimen in a gaseous substance capable of combining with said specimen to form a solid reaction product at elevated temperature and pressure;
- and
- (c) compressing said specimen isostatically while immersed in said gaseous substance to form a compact in which substantially all remaining internal void space is comprised of closed discrete pores.
A method of preparing an aluminum alloy product from a pre-alloyed aluminum powder which comprises:
- (a) reducing the pressure of the atmosphere surrounding a specimen comprising said powder or a porous compact thereof having substantially fully interconnecting pores and purging said specimen with a substantially dry gas, while heating said specimen to volatilize bound species from said specimen;
- (b) immersing said specimen in a gaseous substance capable of combining with said specimen to form a solid reaction product at elevated temperature and pressure;
- and
- (c) compressing said specimen isostatically while immersed in said gaseous substance to form a compact in which substantially all remaining internal void space is comprised of closed discrete pores.
A method of preparing an aluminum alloy product from a pre-alloyed aluminum powder which comprises:
- (a) compressing said powder isostatically to form a porous compact of about 50% to about 80% full density having substantially fully interconnecting pores;
- (b) alternately reducing the pressure of the atmosphere surrounding said compact and purging said compact with a gaseous substance capable of combining with said specimen to form a solid reaction product, while heating said compact to a temperature ranging from about 400.degree. F. to about 1050.degree. F.;
- (c) repeating step (b) at least twice to volatilize and remove substantially all bound species from said specimen, concluding with a pressure of at least about 0.5 torr;
- (d) compressing said compact isostatically at a temperature of less than about 200.degree. F. to form a compact of about 85% to about 99% full density in which substantially all remaining internal void space is comprised of closed discrete pores;
- and
- (e) compressing the product of step (d) to substantially full density at a temperature of from about 500.degree. F. to about 900.degree. F.
Dependencies are inferred from the claim text.