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

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 conventionally casting and suction casting were investigated. The results reveal that the addition of Hf and Ho results in the formation of HfAlNi2 and HoNi2Al3 phases respectively along the NiAl and Cr(Mo) phase interface in intercellular regions. Compared with the conventional-cast alloy, the suction casting optimizes the microstructure of the alloy further, which can be characterized by the refined NiAl/Cr(Mo) eutectic lamellar, high proportion of eutectic cell, and fine and homogeneously distributed HfAlNi2 and HoNi2Al3 phases. In addition, the compression tests show that the suction-cast alloy has better mechanical properties, which can be attributed to the fine microstructure and uniform distribution of the HfAlNi2 and HoNi2Al3 phases.