Deformation behavior and microstructure of DS NiAl/Cr(Mo)alloy containing Hf

A multiphase alloy NiAl–28Cr–5.6Mo–0.1Hf was directionally solidified (DS) in an Al2O3–SiO2 mold by standard Bridgman method. The microstructure, fracture toughness and tensile properties at 980 °C as well as tensile creep in the temperature range 982–1150 °C were studied. The alloy is composed of NiAl, Cr(Mo) and Hf-rich phase and the NiAl and Cr(Mo) interface is not smooth and straight. It was found that the strength of the present alloy was higher than that of many NiAl-based alloys, but the fracture toughness is lower than that of DS NiAl–28Cr–6Mo. The obtained creep curves have similar shape: a short primary creep and long accelerated creep stages. The n and Q for the eutectic alloy calculated from the multiple linear regression analysis are 5.8 and 524 kJ/mol. The rupture properties of DS NiAl–28Cr–5.6Mo–0.1Hf alloy follow the Monkman–Grant relationship.