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 (∼85 vol.-%) with a small amount of FCC phase (∼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 (∼78 vol.-%) and some BCC phase (∼22 vol.-%); in contrast, the SPS processed UFG Al0.8Ti0.2CoNiFe alloy consists of a slightly enriched BCC phase (∼53 vol.-%) and an FCC phase (∼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.
Special theme block on high entropy alloys, guest edited by Paula Alvaredo Olmos, Universidad Carlos III de Madrid, Spain, and Sheng Guo, Chalmers University, Gothenburg, Sweden.
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