Weldability of pure titanium and AZ31 magnesium alloy by friction stir welding

Abstract

Pure titanium and AZ31B magnesium alloy sheets were butt joined by friction stir welding method (FSW) with different joining parameters by tool rotating speed and changing probe position from the joint interface. Al-rich titanium layer with under 2μm in thickness was formed at a joint interface in pure titanium side in the following FSW conditions (travel speed: 300mm/mm, tool rotating speed: 1500rpm, probe position: 1.2mm into titanium). Near the joint interface, the grain of titanium was deformed by both heat effect and stirring force , and vickers hardness of titanium increased to 200 HV 0.05 in comparison with base metal hardness 150 HV 0.05 because of work hardening. However AZ31B showed no obvious hardness change. Tensile strength of the joint increased with changing the prove position into the titanium side and the maximum strength 156 MPa was obtained at probe position of 1.2mm into titanium side. Fracture occurred in the stir zone of AZ31B.