ROLE OF TOOL ROTATIONAL SPEED IN INFLUENCING MICROSTRUCTURAL EVOLUTION, RESIDUAL-STRESS FORMATION AND TENSILE PROPERTIES OF FRICTION-STIR WELDED AZ80A Mg ALLOY

摘要

Joining flat plates of the AZ80A Mg alloy was carried out using the friction-stir-welding technique, employing various speeds of rotation (the tool), and it was observed that an M-shaped distribution characterizes the stress (residual) distributed in the longitudinal direction. Apart from this, the longitudinal stress (tensile) on the advancing side (AS) was found to be larger than that on the retreating side (RS) in the stir zone. It was experimentally recorded that there seem to be a slight increase in the stress values (tensile longitudinal residual), an increase in the tool rotational speed, and an increase in the peak tensile longitudinal stresses at the edge of the shoulder on the AS of the joints. The grain structures in the stir zone were also found to be influenced by the speed of the tool. Observations of fracture surfaces indicated that dimples and ridges resulted in a ductile fracture and quasi-cleavage resulted in a brittle fracture.