Dislocation Dynamics in Aluminum and in Aluminum-Based Alloys Investigated by TEM and NMR Techniques

Abstract

A new attempt has been made to evaluate the yield stress of an alloy containing non-deforming plate-like precipitates. It is based on an application of nuclear magnetic resonance techniques. Since the process of dislocation motion consists of atomic movements nuclear magnetic resonance techniques offer a possibility to determine the manner in which dislocations progress through the solid as a function of time. The spin lattice relaxation rate in the rotating frame, T ⁻¹_1ρ of ²⁷A1 has been measured as a function of the plastic strain rate έ at 77 K. From T_1ρ-measurements which were performed on pure Al, Al-0.1 at% Cu in solid solution and on Al-1 at% Cu containing ө’ plates, the mean jump distance of a mobile dislocation is found. Further, the mean diameter and mean thickness of the ө’ plates were obtained from transmission electron microscopic observations. The yield stress of the Al-1 at% Cu alloy could be predicted by using the NMR and TEM data in a parallel plate model.