Effects of mechanical constraint on the strength of Ni3Ge single crystals

Dislocation structures in Ni3Ge single crystals have been studied after def ormation by [001] compression. In these tests octahedral slips govern the p lastic deformation in absence of resolved stress for cube slips, causing an omalous strengthening throughout the temperature range studied, 77 similar to 500 K. Restriction of the operative shear systems by application of mech anical constraint is shown to increase the work hardening rate for the [001 ] compression. This phenomenon is opposite to the decrease of work hardenin g rate by the imposed constraint found for pure Cu in similar experiments. Three-dimensional dislocation structure has been examined by a high voltage electron microscope. Based on these observations, origin of the rapid work hardening and the anomalous strengthening in Ni3Ge is attributed to a fine and non-planner dislocation structure developed in absence of resolved she ar stress for the cube slips.