Optimization of Friction Stir Welded, Spring Steel Wire Reinforced EN AW-6082 Profile Joints

Abstract

Composite extruded, unidirectionally spring steel wire reinforced profiles have great potential for lightweight applications. Joining of these profiles represents a difficult challenge due to the different material properties, which eliminate fusion welding as a possible joining method. Friction stir welding (FSW) has recently been used to join these profiles, the disadvantage of which is that the reinforcement elements may be bent and fragmented during welding leading to drastically reduced mechanical properties compared to non-joined profiles and even to the unreinforced matrix material. In order to minimize the disturbing influences of the reinforcement elements on the joining strength, the weld axis was shifted to the retreating side, reducing wire-pin contact at the advancing side. As a second remedial measure an insert made of matrix material was placed between the joining partners before joining in order to reduce the contact on both sides. In-situ tensile tests within an X-ray micro computed tomograph (µCT) showed that shifting the weld axis could not improve the joint quality significantly. However, the use of an insert improves the offset yield strength (Rp0.2) by about 50 %.