Deformation and fracture of the PWA 1472 superalloy single crystal

The deformation and fracture of a PWA 1472 single crystal oriented in a sof t orientation were studied by analyzing the evolution of slip bands and der ailed 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 indicate d 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 gam ma'-Ni3Al precipitates. The plastic deformation was heterogeneous and occur red by the propagation of a Luders band. Cleavage fracture occurred along t he kink bands within a coarse shear band that developed after the activatio n of the secondary slip system. An increase in the strain rate did not affe ct the yield strength significantly, but it enhanced the deformation locali zation, and hence, decreased the ductility and increased the percentage of the cleavage facets. The effect of strain rate is discussed in terms of cro ss-slip processes. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Sc ience Ltd. All rights reserved.