DEFORMATION MICROSTRUCTURES IN NI-3(AL, HF)

The dislocation structures resulting from compression tests on Ni-3 (A l, I-If) single crystals are studied as a function of the deformation temperature between 77 and 900 K. Mechanical parameters are also repor ted, such as the 0.2% offset stress, the work-hardening coefficient, t he microscopic activation volume and the dislocation exhaustion rate. The two latter parameters are measured using repeated load relaxation experiments. It is shown that the microstructural features are qualita tively similar to those reported for other Ni3Al compounds: Kear Wilsd orf locks are observed in the temperature domain which corresponds to the strength anomaly, the peak temperature seems to be associated with the occurrence of cube slip. Therefore, the spectacular strengthening due to I-If additions is discussed in terms of other parameters of th e dislocation structure such as the complex stacking fault energy. (C) 1997 Elsevier Science S.A.