Softening mechanisms in ultrasonic treatment of deformed austenitic stainless steel.

The effect of ultrasonic treatment on the microstructural evolution and the related softening process in tensile pre-deformed 316 stainless steel was studied by means of electron backscatter diffraction method, optical microscopy, and microhardness measurement. It was observed that different levels of ultrasonic energy induced complex microstructural changes in the treated samples. A large decrease in twin boundaries was observed, which is an indication of the de-twinning process under ultrasonic treatment.