Abstract
In the present work, NiAl-9Mo alloys with different addition of Zr were prepared by water-cooled copper mold and suction casting, respectively, and the influence on the microstructure and properties of the alloys was discussed. The results show that the microstructure of the as-cast NiAl-9Mo-xZr (x = 0.5, 1.0, 1.5) alloys is a typical eutectic cell structure, with Ni₂AlZr (Heusler) phases discontinuously distributed in the cell boundaries. The eutectic cells of NiAl-9Mo-1Zr alloy prepared by the suction casting process are refined, and the average eutectic lamella thickness is about 3 μm. The microhardness of the suction-cast NiAl-9Mo-1Zr alloy is 630.0 HV, which is higher than that of the as-cast alloy (396 HV). The high-temperature compressive strength of the as-cast NiAl-9Mo-1Zr alloy is higher than that of the as-cast alloy, which reaches 350 MPa at 1273 K, due to the joint action of fine grain strengthening and the second phase strengthening of the Heusler phase.

Key words
NiAl alloy, suction casting, microstructure, grain refinement, high-temperature strength

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