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 Ni2AlHf and Ni2Al3Ho 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 Ni2AlHf and Ni2Al3Ho 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 Ni2AlHf and Ni2Al3Ho phases and solid solubility extension.