Synergetic strengthening of coherent and incoherent interface on a mixed-phase high-entropy alloy revealed by micro-pillar compression
Wei Zhang, Zhichao Ma, Dongni Liu, Shenghui Wang, Hongwei Zhao, Luquan Ren
Abstract
Mechanical properties at small scale of mixed-phase Fe24Co25Ni24Cr23Al4 high-entropy alloy (HEA) were examined by micro-pillar compression tests in nano-indentation system. The micro-pillars with diameter of 400 nm were fabricated in the individual face centered cubic (FCC), body centered cubic (BCC) and their interfacial region employing a focused ion beam (FIB) technology. A combination of scanning electron microscope and transmission electron microscopy was performed on the deformed micro-pillars to determine the micro/nano structures. The interfacial pillars exhibited higher strength as compared with single BCC and FCC pillars according to the stress–strain responses during compression, which was attributed to the synergetic strengthening of FCC/BCC incoherent interface and A2/B2 coherent interface in mixed-phase pillar. The observed B2 particles inside BCC were induced by the spinodal decomposition. Moreover, a large number of dislocations pile-up against interface, indicative of the strengthening of the interface.