CHARACTERISTICS OF PLASTIC-FLOW IN NI-3(AL,HF) SINGLE-CRYSTALS

Characteristic parameters of plastic deformation have been measured fo r Ni-3(Al,Hf) single crystalline specimens deformed in compression ove r a wide range of temperatures (293-1100 K). These parameters are: (1) the resolved proof stress (tau(0.2%)) which is measured at 0.2% offse t stress; (2) the corresponding work-hardening rate (theta(0.2%)); (3) the microscopic activation volume (V-0.2%); and (4) the variation in the density of mobile dislocations (Delta rho(m)/rho(m0.2%)) during tr ansient tests such as load relaxations. The two last parameters were d etermined with a technique of repeated load relaxations. It is observe d that not only tau(0.2%) exhibits an anomalous behaviour with tempera ture but also theta(0.2%) and Delta rho(m)/rho(m0.2%). A comparison of V-0.2% (tau) with similar measurements in Ni3Al shows that alloying e ffects alter the deformation mechanism. (C) 1997 Elsevier Science S.A.