Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Post sintering operation
Patent
1987-07-06
1988-08-09
Lechert, Jr., Stephen J.
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Post sintering operation
73863, 73866, 419 31, 419 38, 419 48, 419 49, 419 53, 419 54, 419 60, B22F 324
Patent
active
047626798
ABSTRACT:
A process for manufacturing powder metallurgy (P/M) preforms which are conditioned for optimum intrinsic workability is described which comprises steps of heating a quantity of P/M material in a can to a first preselected temperature under vacuum to degas the material, compacting the canned material at a second preselected temperature under pressure to provide a compact of the material; or cold compacting the powder to about 75% density and degassing it at suitable temperature and then vacuum hot pressing the powder at about 0.75 melting point; generating flow stress data as a function of strain rate and temperature on samples of the compact at predetermined strain within predetermined ranges of temperature and strain rate and determining powder dissipation efficiency of the compact and entropy rate ratio within those ranges of temperature and strain rate; selecting values of strain rate and extrusion temperature at which dynamic recrystallization is the dominant metallurgical mechanism characterizing the compact: and extruding the compact in an extrusion can at the selected extrusion temperature and at an extrusion rate corresponding to the selected strain rate using a streamlined die. An improved processing map for preselecting optimum processing parameters for the material is described.
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Barker Douglas R.
Doraivelu Sokka M.
Gegel Harold L.
Gunasekera J. S.
Lark Kristine A.
Lechert Jr. Stephen J.
Scearce Bobby D.
Singer Donald J.
The United States of America as represented by the Secretary of
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