Deformation and fracture of the PWA 1472 superalloy single crystal

The deformation and fracture of a PWA 1472 single crystal oriented in a soft orientation were studied by analyzing the evolution of slip bands and derailed fractography of tensile specimens tested at low (10(-4)/s) and high (1.0/s) strain rates at room temperature. The results of this study indicated that the slip did not start on the system with the highest Schmid factor. This yielding anisotropy has been attributed to the deformation of the gamma'-Ni3Al precipitates. The plastic deformation was heterogeneous and occurred by the propagation of a Luders band. Cleavage fracture occurred along the kink bands within a coarse shear band that developed after the activation of the secondary slip system. An increase in the strain rate did not affect the yield strength significantly, but it enhanced the deformation localization, and hence, decreased the ductility and increased the percentage of the cleavage facets. The effect of strain rate is discussed in terms of cross-slip processes. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.