Microstructure and Corrosion Behavior of Friction Stir Welded Mg/Al- and M g/Mg-Joints

摘要

Friction stir welding (FSW) is a well suited solid state welding process to produce high-quality light weight metal joints. In the present work the developing microstructure between AZ91-Mg-alloy and AA5454-Al-alloy is presented. SEM investigations and EDX element mappings as well as temperature measurements during the welding process have been carried out to describe the welding zone in detail and to develop a phase-diagram which indicates the fractures of the possible appearing phases in the hybrid joints. Microstructural investigations showed that under load the cracks are predominantly initiated at the intermetallic phases precipitated as interlayers in the contact areas between the two alloys. Furthermore the corrosion behavior of the friction stir welding zone of the hybrid joints and of die-casted Mg/Mg-joints (AZ91D and MRI153M) was examined. The results showed that the corrosion behavior for hybrid joints is completely different in comparison to the base material.