Effect of friction stir processing on microstructure and mechanical properties of laser-processed Mg-4Y-3Nd alloy

The development of advanced structural materials is dependent, among many factors, on the choice of manufacturing processes. Laser processing and friction stir processing (FSP) are two such advanced manufacturing processes. Individually, they have been studied quite extensively to understand their potential for developing high efficiency structures. However, there is no study describing the sequential integration of laser processing and FSP on microstructure and mechanical properties. The present study deals with FSP of the laser processed Mg-4Y-3Nd (WE43) alloy. The laser surface melting was carried out in air at 1800 W laser power, 30 mm/s laser speed, and 0.6 mm spot size on the surface using continuous wave Nd:YAG fiber laser followed by FSP of laser processed region at 500 rpm and 4 ipm. Scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy were carried out to understand microstructural evolution within the laser melted and friction stir processed regions. Mechanical properties were evaluated using uniaxial tensile testing at a strain-rate of 10(-3) s(-1). FSP led to significant improvement in strength and ductility of the laser processed material. An analysis of the strengthening mechanisms revealed that the dominant strengthening mechanism(s) in the WE43 alloy was dependent on the processing step. (C) 2016 Elsevier Ltd. All rights reserved.