Creep behaviour of a Ni15Cr solid solution alloy at low stresses and intermediate temperatures

Creep in a Ni15Cr solid solution alloy at low stresses and intermediate temperatures was investigated using the helicoidal spring specimen technique. The applied stress ranged from 0.2 to 5.0 MPa, the testing temperatures from 973 to 1123 K (homologous temperatures TTm from 0.59 to 0.65, where Tm is the solidus temperature). The intercept grain size of creep specimens ranged from 47 μm to 254 μm. It was found that under the above conditions, viscous creep of the Bingham type occurs, characterized by a low threshold stress which decreases with increasing temperature. The temperature, applied stress and grain-size dependence of the steady-state creep strain rate can be interpreted in terms of the transition from Coble diffusional creep to Harper-Dorn dislocation creep controlled by dislocation core diffusion.