Nonlinear Acoustic Assessment of Precipitation-Induced Coherency Strains in Aluminum Alloy 2024

Abstract

There currently exists no direct in situ method for nondestructively assessing the optimum heat treatment time for precipitation strengthening of bulk alloy material. We report here progress on our investigation of nonlinear acoustic methods as a nondestructive means of determining maximum material strengthening during the artificial aging of metallic alloys. We present the elements of an analytical model that predict the effects of precipitation-induced coherency strains generated during heat treatment on the magnitude of acoustic second harmonic signals. The predictions of the model are compared to experimental measurements of aluminum alloy 2024 artificially aged from T4 to T6 temper.