Microscopic Investigation of Crack Propagation Under Static Load on a Precipitation Hardenable Austenitic Steel with About 6% Al and 40% Ni.

The purpose of this investigation was to determine the tendency of the steel for nonhomogeneous deformation as a function of structural condition and to explain the effect of this tendency on crack propagation by microscopic investigations of the slip processes in nonhomogeneous stress field at the tip of the crack. The steel was tested in eight different structural conditions. The surfaces and the fractures of 1. 5 mm thick flat tensile specimens were investigated by microscopy, and crack propagation in 0. 3 mm thick foil was directly observed by electron microscope transmission. Results are illustrated and analyzed.