Mechanical behaviors of NiAl-Cr(Mo)-based near eutectic alloy with Ti, Hf, Nb and W additions

Effects of Ti, Hf, Nb and W alloying elements addition on the microstructure and the mechanical behaviors of NiAl-Cr（Mo） intermetallic alloy were investigated by means of XRD, SEM, EDX and compression tests. The results show that Ni-31Al-30Cr-4Mo-2（Ti, Hf, Nb, W） alloy consists of four phases： NiAl, ？？Cr solid solution, Cr2Nb and Ni2Al（Ti, Hf）. The mechanical properties are improved significantly compared with the base alloy. The compression yield strength at 1 373 K is 467 MPa and the room temperature compression ductility is 17.87% under the strain rate of 5.56？？0-3 s-1, due to the existence of Cr2Nb and Ni2Al（Ti, Hf） phases for strengthening and Ti solid solution in NiAl matrix and coarse Cr（Mo, W） solid solution phase at cellular boundaries for ductility. The elevated temperature compression deformation behavior of the alloy can be properly described by power-law equation： ε=0.898 σ8.47exp[-615/（RT）].

Microstructure and mechanical properties of Nb-doped NiAl-Cr(Mo) eutectic prepared by injection casting

The microstructure, compressive properties at different temperatures and hardness of NiAl-Cr（Mo）-Nb alloy prepared by injection casting were investigated. Compared with the conventionally-cast alloy, the injection-cast alloy exhibits a fine microstructure, i.e. the fine eutectic cell and interlamellar spacing as well as fine primary NiAl phase and NbCr2-type Laves phase due to the high cooling rate. In addition, the area fraction of eutectic cell increases due to the narrow intercellular zone. The Vickers hardness of injection-cast alloy is markedly enhanced. The ductility and strength at room temperature are increased by 88% and 30% compared with those of conventionally-cast alloy respectively. However, the high-temperature strength of injection-cast alloy is not improved markedly. The elevated temperature compression deformation behavior can be properly described by power-law equations.