Effect of Heat Treatment on Microstructure and Microhardness of Directionally Solidified NiAl-Cr(Mo)-Hf Intermetallic Alloy

摘要

The effect of heat treatment on microstmcture and microhardness of directionally solidified (DS)NiAl-Cr(Mo)-Hf alloy is investigated. The results indicate that there is little change in the morphology of NiAl and Cr(Mo) phases after heat treatment. However, the semicontinuous Heusler phase which is originally located at grain boundaries is partially reduced and fine Heusler particles re-precipitate within NiAl matrix. Furthermore, NiAl precipitates coarsen in Cr(Mo) phase and dislocations appear in Cr(Mo) phase. Microhardness of as-grown (DS)NiAl-28Cr-5Mo-lHf alloy is much higher than that of (DS)NiAl-28Cr-6Mo and basically has no change after heat treatment.