Effect of growth rate on the tensile properties of DS NiAl/Cr(Mo) eutectic alloy produced by liquid metal cooling technique

An eutectic multiphase alloy NiAl–28Cr–5.94Mo–0.05Hf–0.01Ho (at.%) was directionally solidified by liquid metal cooling technique at withdrawal rates of 3, 8 and 10 mm min−1. The microstructure and tensile properties of alloys at room temperature, 1253 K and 1373 K were investigated. With the increase of withdrawal rate, the microstructure was refined including the refinement of eutectic cells and lamellae between the NiAl and Cr(Mo) phases. At room temperature, the alloys fractured as cleavage mode. At 1253 K, yield behavior occurred which lead to higher of tensile strength and ductility compared to those at room temperature, and the properties are independent of withdrawal rate. At 1373 K, tensile properties increase with the increase of withdrawal rate, and both the strength and elongation rate are lower than those at 1253 K. The mechanisms responsible for these changes were discussed.