Mechanical property of single phase Co-Ni-Cr-Mo based superalloy produced by cold working and recrystallization heat treatment

Mechanical property of carbon-free Co-Ni-Cr-Mo based superalloy was investigated at room temperature and at 943 K. Cold working and subsequent recrystallization heat treatment was carried out to produce an equiaxed grain structure. The average grain size was controlled to 28 and 238 μm in order to understand the effect of grain size on mechanical property and flow behavior. At room temperature and 943 K, 0.2% offset yield strength increased with decreasing grain size to exhibit grain size dependence. At 943 K, a specimen with the average grain size of 28 μm showed higher yield strength than that obtained with a specimen having the average grain size of 238 μm. A steady-state like behavior leading to an extensive ductility was observed in the fine-grained specimen. {111 }〈112〉 deformation twinning was found to correlate with the steady-state like behavior in the true stress-true strain curve. It was suggested that grain refinement is favor to enhance the fracture strength and allow the deformation twinning to occur.