Effects of V addition on the solidification microstructures and room temperature compression properties of NiAl–Cr(Mo) hypereutectic alloy

Abstract

The solidification microstructures and compression properties of NiAl–32Cr–6Mo and NiAl–36Cr–6Mo hypereutectic alloys with different V additions were studied. The results show that V addition did not change the constitute phase. However, the primary Cr(Mo) phase began to show obvious dendritic morphology, the formation of the eutectic lamellae was disturbed, and the microstructure of the eutectic cell was degraded. The EDS result indicated that all V solubilized in the Cr(Mo) phase. As the V addition increased, the volume fraction of the primary Cr(Mo) phase and the solid solution content of V in the Cr(Mo) phase continued to increase. Due to the solid solution strengthening of V in the alloy, the compression properties of V-doped alloys were obviously improved. Especially, the NiAl–32Cr–6Mo–1V alloy simultaneously had the highest compression strength of 1816 MPa and compression strain of 18.4%. When the V content further increased, although the positive effect due to the solid solution strengthening increased, the increasing number of primary Cr(Mo) dendrites in the alloy would result in decreased compression properties. In addition, all alloys showed brittle quasi-cleavage fracture pattern, while crack bridging, crack deflection and shear ligament were observed in the NiAl–32Cr–6Mo–1V alloy.