Mechanical response of as-cast equiatomic high entropy alloy CuFeCoNiMn

The mechanical behavior of a cast CuMnNiFeCo high entropy alloy, with larger grains and 0.5% (by volume) of micro-porosities, was investigated at room temperature under a unidirectional tensile load. The initial micro-structural features show two types of the Face Centered Cubic (FCC) structure (FCC-1 and FCC-2), corresponding to the dendritic arms, in the as-cast alloy, exhibiting two different contrasts. FCC-1 shows the presence of the elements, Cu, Mn, and Ni; while FCC-2 contains, Fe, Co, and Ni. The cast alloy, in spite of the large grain size and a significant fraction of micro-porosities, shows high strength along with good ductility. The response of the cast alloy, under tensile deformation, was examined from the engineering stress-strain and true stress-strain plots. The hardening curve, derived from the true stress-strain plot, shows three parts, as a function of the true stress (and hence, true strain). Microstructural investigations indicate that the formation and growth of deformation twins, which restrict dislocation mobility, could be behind the hardening response. The stress (strain) levels on both sides of the intermediate level undergo dislocation-dominated deformation. It appears that elemental segregation may provide respite from early failure starting from the micro-porosities. In fact, Cu - rich regions have been observed to behave like a flow line, connecting one micro-porosity with another, thereby preventing them from opening up under the deformation load.

Automated summary

The mechanical behavior of a cast CuMnNiFeCo high entropy alloy with larger grains and micro-porosities was investigated at room temperature. Despite the presence of large grain size and micro-porosities, the alloy exhibited high strength and good ductility. The formation and growth of deformation twins may contribute to the hardening response of the alloy.