Effect of Hf on microstructure and high-temperature strength of a cast NiAl/Cr(Mo) alloy

A NiAl/Cr(Mo) alloy modified with Hf was fabricated by a vacuum induction m elted and drop cast. The alloy was mainly composed of NiAl matrix, Cr(Mo) a nd Hf-rich phase distributed between NiAl and Cr(Mo) phase boundary and pha se transition was also studied. Then it was hot isostically pressed (HIPed) at 1523 K, 200 MPa for 4.5 h. Its high temperature compressive behavior wa s studied and the deformation features of the alloy could be adequately des cribed by standard power law which is usually used to characterize creep be havior for various metallic material, The stress exponent n as well as the activation energy Q was calculated by fitting the experimental data to the power-law and temperature-compensated power lax equation, The possible stre ngthening mechanism was discussed.