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

Abstract Characteristic parameters of plastic deformation have been measured for Ni 3 (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 ( τ 0.2% ) which is measured at 0.2% offset stress; (2) the corresponding work-hardening rate ( θ 0.2% ); (3) the microscopic activation volume ( V 0.2% ); and (4) the variation in the density of mobile dislocations (Δϱ m /ϱ m 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 τ 0.02% exhibits an anomalous behaviour with temperature but also θ 0.02% and Δϱ m /ϱ m 0.02%. A comparison of V 0.02% (τ) with similar measurements in Ni 3 Al shows that alloying effects alter the deformation mechanism.