Microstructural verification of the theoretically predicted morphologies of the NiAl–Cr pseudo-binary alloy systems and NiAl–Cr eutectic structure modification by Mo addition

Based on the NiAl–Cr pseudo-binary phase diagram, ranging from hypo- to hyper-eutectic areas, alloys with various compositions were produced by arc melting. The microstructures were compared with the theoretical predictions of Tang et al. (Chem Chem Phys 18(29):19773–19786, 2016) and they were proved to be in agreement. The partial substitution of Cr by Mo in three different compositions revealed eutectic and hypo-eutectic microstructures with the eutectic micro-constituent modified from fibrous to lamellar. The importance of T0-A2 and T0-B2 temperatures [the maximum temperatures under which, partitionless solidification of A2 and B2 phases respectively happens (Laughlin and Hono in Physical metallurgy, Elsevier, Amsterdam, 2014)] and their relation to Te (eutectic temperature) proved to be the dominant factor that shifts the microstructures to off equilibrium morphologies in the case of NiAl–Cr alloys.