Simulation and experimental study of underwater dissimilar friction-stir welding between aluminium and steel

Abstract

The volume of fluid (VOF) modeling method was implemented to simulate the underwaterfriction-stir welding (FSW) process for dissimilar joining between aluminum and steel. Tem-perature profile, materials flow, and intermixing during dissimilar bonding under the coolingmedium were monitored via VOF modeling and verified according to experimental data. Theeffects of processing parameters on the formation of intermetallic compounds (IMCs) atthe Al/St interface, microstructural characteristics, and mechanical property of dissimilarweldments were studied and addressed. By decreasing tool rotational speed (w), increas-ing traverse velocity (v), and employing cooling medium, peak temperature continuouslyreduced (down to ?473 and 573 K for the aluminum and steel sides, respectively) led to sub-stantial refining the grain structure and formation of a thinner IMC layer. The average grainsize in the aluminum and steel sides of SZ is refined down to ?4 and 12-m, respectively. Thethickness of the IMC layer varied depending on the processing parameters with the lowestvalue of ?0.2-m. The formation of a curved interface due to enhanced materials mixing atthe advancing side is noted with a linear hardness gradient across the dissimilar weldment.Superior mechanical strength of ?80 MPa attained at an optimized submerged condition ofw = 1650 rpm/v = 40 mm/min showed combined ductile-brittle fractographic aspects on thefracture surface. 2020 The Authors. Published by Elsevier B.V.