EFFECTS OF POST-WELD HEAT TREATMENT ON THE MECHANICAL PROPERTIES OF AA6061 FRICTION STIR WELDED JOINTS

摘要

Unique combination of properties in aluminum alloys, including low density, high strength-to-weight ratio, good formability, corrosion resistance and recyclability, have allowed their increasing application for light-weighting of components in the transportation sector. Widespread application has, however, been limited by the low weldability of high strength aluminum alloys, such as crack sensitive grades of the 2XXX, 6XXX and 7XXX series. As a solid-state joining technology, friction stir welding (FSW) presents a tremendous potential for the assembly of 6XXX series aluminum alloy (AA) structures due to the low heat input involved in this process, which allows lower welding-induced distortions and improved mechanical performance of the joint. In this work, 3.18 mm thick AA6061-T6 sheets were assembled by FSW and the resulting mechanical properties of the joint were measured at room temperature. It was determined that the softening in the weld nugget resulted in a reduction in the yield and tensile strengths of the weldment. The application of a post-weld heat treatment was demonstrated to be an effective strategy for restoring the mechanical properties close to the base metal values.