The Influence of Parameters Affecting Mechanical Properties and Microstructures of Semi-Solid-Metal 7075 Aluminum Alloy by Using Friction Stir Spot Welding

摘要

This research aims to study the influence of parameters that affect the mechanical properties of semi-solid-metal 7075 aluminum alloy with friction stir spot welding process. The parameters fort this experiment such as rotation welding speed at 380, 760, 1240 and 2500 rpm and rotation welding time at 60, 90 and 120 seconds were employed respectively. The study found that the welded specimens at all the conditions can be welded very well. Moreover, friction stir spot welding process showed that the hardness in weld zone had an average value at 79.83 HV which is lower than the hardness of the base metal. The shear tensile strength of the welded specimens had the average value approximately 194.20 MPa at rotation welding speed of 1240 rpm, rotation welding time of 120 seconds and plunge of depth of 2 millimetres. The microstructure in the weld zone and thermal mechanical affected zone were deformed permanently. Therefore, friction stir spot welding process of this aluminum alloy provided good effects on mechanical properties. Statistical analysis showed that the coefficient of determination R-square was equal to 93.50 percent. This means that the variations of the experiments were controllable, such as equipment or other factors in the experiment. For the remaining, only 6.50 percent was uncontrolled factors.