Effect of plastic deformation on nonlinear ultrasonic response of austenitic stainless steel

The effect of tensile plastic deformation on the nonlinear ultrasonic response of austenitic stainless steel was examined, using nonlinear longitudinal wave. The plastic deformation induced the formation of twins and martensite needles in grains. The density of martensite needles increased with increasing plastic strain. The nonlinear ultrasonic parameter increased with increasing the plastic strain experienced by plastically deformed austenitic stainless steel. A simple power-law relation was proposed between the nonlinear ultrasonic parameter and the plastic strain, taking account of the contribution of local microstructures and microplastic deformation. Using this relationship, the stress exponent index was found to be 1.55. Considering the contributions of local microstructures, the deformation-induced phase change and the deformation associated with the formation of new phase, it is suggested that the acoustic nonlinearity of heterogeneous materials depends on local microstructures, phases, misfit, and high-order elastic constants of individual phases. (C) 2014 Elsevier B.V. All rights reserved.