Microstructure and mechanical properties of NiAl–Cr(Mo)–Hf/Ho near-eutectic alloy prepared by suction casting

Abstract The microstructure and mechanical properties of 0.15 at.% Hf and 0.2 at.% Ho doped Ni-33Al-28Cr-6Mo near-eutectic alloys prepared by conventional casting and suction casting were investigated. The results reveal that the addition of Hf and Ho results in the formation of Ni 2 AlHf and Ni 2 Al 3 Ho phases, respectively, along the NiAl and Cr(Mo) phase interface in intercellular regions. Compared with the conventional-cast alloy, the microstructure of suction-cast alloy is well optimized, characterized by the thin interlamellar spacing, high proportion of eutectic cell area and fine homogeneously distributed Ni 2 AlHf and Ni 2 Al 3 Ho phases. Furthermore, the room temperature mechanical properties of the suction-cast alloy improve significantly, which can be attributed to fine microstructure, uniform distribution of the Ni 2 AlHf and Ni 2 Al 3 Ho phases and solid solubility extension.