Powder Metallurgy Processing of Ti-48Al-2Nb-2Cr(at%) Alloys
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POWDER METALLURGY PROCESSING OF Ti-48Al-2Nb-2Cr(at%) ALLOYS G.E. Fuchs General Electric Company, P.O. Box 1072, Schenectady, NY 12301-1072
ABSTRACT The effect of processing on the microstructures and properties of powder metallurgy processed Ti-48Al-2Nb-2Cr alloys was examined. Both gas atomization (GA) and plasma rotating electrode process (PREP) techniques were used to produce pre-alloyed powder of the desired composition. The powders were then consolidated by either HIPing or extrusion. The effects of HIP temperature (1090 0 -1300 0 C) and HIP pressure (103MPa and 172MPa) were examined during HIP consolidation of GA powders. In addition, some of the PREP and GA HIPed materials were subsequently hot worked by isothermal forging. The tensile properties of these materials were determined in air in the temperature range 25O. 1000 0 C. These results were then compared with previous data for I/M materials. The inter-relationship of processing, microstructure and properties was examined.
INTRODUCTION Due to their low density, high strength, and oxidation resistance, TiAl-based alloys are candidate materials for elevated temperature applications [1]. A significant amount of alloy development has been reported and reviewed [2-4]. However, the vast majority of this work has been performed on ingot metallurgy (I/M) processed materials. Only a limited amount of work has been reported on powder metallurgy (P/M) processing [5-12]. Much of the P/M work has emphasized the microstructure of as-solidified and heat treated powder particles [6,7,10,11]. The purpose of this study is to evaluate the microstructure and tensile properties of near-gamma (ctJy) alloys with similar nominal compositions processed by two powder metallurgy techniques.
EXPERIMENTAL PROCEDURES Pre-alloyed powders with a nominal composition of Ti-48Al-2Nb-2Cr (at%) were prepared by both gas atomization (GA) and plasma rotating electrode process (PREP) techniques (Tables 1 and 2) and consolidated by hot isostatic pressing (HIP) or extrusion. The -35 mesh (
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