Influence of Cr removal on the microstructure and mechanical behaviour of a high-entropy Al0.8Ti0.2CoNiFeCr alloy fabricated by powder metallurgy

摘要

We report a systematic study on the influence of Cr removal on the microstructure and mechanical behaviour of an ultra-fine grained (UFG) high-entropy alloy (HEA), Al0.8Ti0.2CoNiFeCr, fabricated via spark plasma sintering (SPS) of mechanically alloyed (MA'ed) powders from constituent elemental powders. The MA'ed Al0.8Ti0.2CoNiFeCr powders consist principally of a BCC phase (similar to 85 vol.-%) with a small amount of FCC phase (similar to 15 vol.-%), whereas the MA'ed Al0.8Ti0.2CoNiFe powders present similar phases to those in the MA'ed Al0.8Ti0.2CoNiFeCr powders. Interestingly, the SPS processed UFG Al0.8Ti0.2CoNiFeCr alloy contains mostly an FCC phase (similar to 78 vol.-%) and some BCC phase (similar to 22 vol.-%); in contrast, the SPS processed UFG Al0.8Ti0.2CoNiFe alloy consists of a slightly enriched BCC phase (similar to 53 vol.-%) and an FCC phase (similar to 47 vol.-%). In addition, the SPS processed Al0.8Ti0.2CoNiFe alloy exhibits slightly higher yield strength, compressive strength and hardness but lower plasticity than those of the SPS processed Al0.8Ti0.2CoNiFeCr alloy.