SEM investigation of the microstructure of cast CuNiAlCoFe equiatomic high entropy alloy

Abstract

Microheterogeneity and crystallization conditions of the equiatomic high-entropy CuNiAlCoFe alloy were studied by measuring the viscosity during heating/cooling, as well as visualizing the microstructure after solidification. The CuNiAlCoFe liquid alloy showed different temperature dependences of viscosity upon heating to 2070 K and subsequent cooling. Since the coinciding part of the temperature dependences was absent, complete destruction of the microheterogeneity of the melt after heating to 2070 K did not occur. Heating the melt to higher temperatures was not possible due to the evaporation of the metal. The melt viscosity during cooling is higher than that during heating; this is observed when microheterogeneity is dispersed. The CuNiAlCoFe alloy obtained as a result of the experiment at a crystallization rate of 10 K/s had a typical microstructure of cast dendrite. Dendrites consisted of a eutectic (α-Al+CuAl2+Cu4NiAl7) and included primary crystals of CoCu2Al7 and FeCu2Al7. The interdendritic space contained small Cu4NiAl7 crystals. © Published under licence by IOP Publishing Ltd.