A Fundamental Study of P/M Processed Elevated Temperature Aluminum Alloys.
Annual technical rept. 1 Oct 81-30 Sep 82,
DREXEL UNIV PHILADELPHIA PA DEPT OF MATERIALS ENGINEERING
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Aluminum alloys exhibiting high strength and improved creep resistance at elevated temperatures offer the potential for lower weight and reduced cost in aerospace components. Powder processing, involving controlled atomization and hot consolidation, provides a means for fabricating candidate alloys the microstructure consists of a stable fine-scale uniform dispersion of intermetallics in the aluminum marix. Retention of elevated temperature strength has been demonstrated in a PM Al-Fe-Ni alloy. Atomized powder is characterized by a duplex microstructure of fine and coarse regions of FeNiAl9 Vf approximately 0.3 in the aluminum matrix. The fine microstructure is harder than the coarse microstructure and is table up to approximately 350 C, above which its hardness decreases rapidly. There is a gradual coarsening and decrease in hardness of the initially coarse regions with increasing temperature. The duplex microstructure is carried over into the hot pressed and extruded material. Changes in microstructure and hardness of the extruded material during elevated temperature exposure are similar to those occurring in the powder form. Hot tenisle test data up to 400 C indicate that the extruded material retains approximately 60 of its ambient strength up to approximately 250 C with ductility approaching 10. This reflects a promising level of structural stability. These results and observations can be explained in terms of particle cooling rate, precipitation of aluminides, and aluminide coarsening during powder processing powder consolidation temperatures should be kept as low as possible. Author
- Properties of Metals and Alloys