An attempt to develop a double-layered AZ91 build structure through severe plastic deformation route

Abstract

In this preliminary investigation, a double-layered AZ91 magnesium structure was developed using solid-state friction stir additive manufacturing (FSAM) by varying the tool rotation speed and traverse speed. Cross-sections of the samples were examined using optical macroscopy, while hardness was measured using a Vickers hardness tester. X-ray diffraction analysis was conducted for the identification of secondary phases, and transmission electron microscopy was used for micro-structural analysis. The results showed varied material consolidation with respect to the processing conditions. Defect-free structures were obtained at 800 rpm-25 mm/min and 900 rpm-30 mm/min. Maximum hardness of 127.2 HV (average) was observed along the build developed at 800 rpm-25 mm/min, with crystallite size reducing from 96.4 to 21.2 nm. Finer grains and the dispersed β phases contributed mainly to property enhancement, while the dislocation density decreased post-FSAM, due to heat input.