Study of Process Characteristics of Friction Stir Lap Welded AZ31B Alloy and AISI304

Abstract

The weight reduction by improving the material properties is always a challenge which has been achieved by joining of lightweight materials. Some steel components can be replaced by lightweight materials like magnesium alloy. Magnesium has low density and high strength to weight ratio. The main difficulty in joining of magnesium and steel with traditional fusion welding techniques is their melting point difference of 900℃ and low solubility. To solve the problem of joining of dissimilar metals, the solid-state welding such as Friction stir welding has potential to join these materials. In this work, the process characteristics were studied for Friction Stir Welding of Magnesium alloy (AZ31B) and Stainless steel (AISI304) in lap configuration. Various sets of experiment were carried to study the effect of process parameters i.e., plunge depth and tilt angle on force, temperature, mechanical strength and microstructure, grain structure. Tensile test and micro-hardness indentation have been carried out to evaluate the mechanical properties. Later the joint interface has been characterized with the help of SEM, XRD and optical microscopy. Results suggested deeper penetration of tool has detrimental effect on the mechanical strength due to excess hooking effect. Also grains refinement has been found in the welded region. XRD results indicated formation of inter-metallic compound at the joint interface.