Tensile properties and microstructure of in situ NiAl–Cr (Zr) eutectic composite

An in situ NiAl–33.5Cr–0.5Zr composite was prepared by vacuum induction melting followed by hot isostatical pressing (HIP) at 1573 K and 100 MPa for 3 h. The microstructure of the composite is composed of NiAl matrix and Cr phase with small amount of Ni2AlZr and Zr-rich phases distributing at the interfaces of NiAl and Cr phases. It is found that the composite is stronger and more ductile than that of some NiAl-based alloys at high temperature. However the composite is still brittle at room temperature and becomes ductile with the increase of testing temperature. The brittle-to-ductile transition temperature (BDTT) is the function of initial strain rate. Under the creep deformation at 1273 K and 100 MPa, the minimum creep rate of the composite is three orders lower than that of the polycrystalline NiAl and single crystalline NiAl [0 0 1]. TEM observations on the deformed samples of both tension and creep show that dynamic recrystallization has occurred during high temperature deformation process.