Characteristics of plastic flow in Ni3(Al,Hf) single crystals

Characteristic parameters of plastic deformation have been measured for Ni3(Al,Hf) single crystalline specimens deformed in compression over a wide range of temperatures (293–1100 K). These parameters are: (1) the resolved proof stress (τ0.2%) which is measured at 0.2% offset stress; (2) the corresponding work-hardening rate (θ0.2%); (3) the microscopic activation volume (V0.2%); and (4) the variation in the density of mobile dislocations (Δϱm/ϱm 0.02%) during transient tests such as load relaxations. The two last parameters were determined with a technique of repeated load relaxations. It is observed that not only τ0.02% exhibits an anomalous behaviour with temperature but also θ0.02% and Δϱm/ϱm0.02%. A comparison of V0.02% (τ) with similar measurements in Ni3Al shows that alloying effects alter the deformation mechanism.