Influence of Cooling Methods in Friction Stir Welding of 7075 Aluminum Alloy

Abstract

Regarding various part manufacturing in industrial scale, one of the most popular processes was welding, especially in automotive and aircraft industries. It was well known that these industries have an increasing rate of aluminum consumption every year. There was due to aluminum has many outstanding properties such as light weight, high strength to weight ratio and very good elongation. One of the most used aluminum alloys was AL7075, which is suitable for highly stressed structural applications in aircraft structural parts. However, fusion welding techniques were usually yielded poor strength for such grade of aluminum. Friction stir welding is a solid-state welding technique that joins two workpieces without melting the workpiece material. Heat was generated by friction between the shoulder of the stirring tool and the workpiece. The probe was to stir and mix two metals parts together. However, the Thermo Mechanical Affect Zone (TMAZ) and Heat Affect Zone (HAZ) were reported as the weakest area of welded parts. Therefore, this study aims to improve the joints by cooling processes during welding using cutting fluid and cryogenic cooling with different parameters such as welding speed and shoulder size. The results of these experiment indicated that the cooling process influenced the mechanical properties of the joints. The micro-vicker hardness showed a significant increase in TMAZ and HAZ area.