Surface Plastic Deformation and Nanocrystallization Mechanism of Welded Joint of 16MnR Steel Treated by Ultrasonic Impact

Abstract

The welded joint surfaces of 16MnR steel were treated using an ultrasonic impact machine. The effects of ultrasonic impact treating (UIT) on the plastic deformation and nanocrystallization mechanism of the welded joints of 16MnR steel were studied. The micro-structural features of the surface layer produced by UIT were observed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM), and micro-hardness measurements were performed. Experimental results showed that the thickness of the plastic deformation layer was approximately 80 μm. It was found that grains in the surfaces of the welded joints of 16MnR were greatly refined by UIT. Obvious grain refinement was observed, with resultant gain sizes less than 100nm. The micro-hardness of the treated surface layer of the welded joint was enhanced significantly compared to that of the un-treated sample. The micro-hardness on the treated surface of the welded joint was 62.3% higher than that of the un-treated surface.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9563

Keywords

• nanocrystallization, mechanism, 16MnR, ultrasonic impact, welded joint