Friction Welding of Semi-Solid Metal 7075 Aluminum Alloy

Abstract

The purpose of this study is to evaluate the welding characteristic of friction welded similar joints of SSM7075 aluminum alloys. Friction welding methods were investigated by joining parameters as follows: rotational speed of 1200, 1400, 1600, and 1800 rpm, burn of length of 2.5, 3.0, and 3.5 mm, feed rate of 0.2 mm/min, and welding time for 15 seconds respectively. The results of the investigation have shown that joining parameters with rotational speed of 1800 rpm, burn of length of 3.5 mm, and 15 seconds of welding time can produce a very good weld with the highest joint strength at 104.53 MPa., which had joint efficiency for 63 percent compared with base metal. The results of this investigation have shown that an average hardness is around 140.31 HV in weld zone. Examination of the joint region using SEM showed the microstructure in weld zone after welding is fine structure; both aluminum phase (α) and eutectic phases (MgZn2) from SSM7075 Aluminum alloys have mixed together. The eutectic phases in weld zone are an elongated and plate-like shape of MgZn2 particles, which was destroyed by frictional force as fractures of the eutectic phases. After friction welding, the particle size is around 1.518 μm long and 1.140 μm wide and it was also found that MgZn2 fractures are evenly distributed in welded zone. However, after friction welding process, it was found that grain structures in welded zone are refined from globular structures into fine structures.