Fabrication and effect of Mg–Zn solid solution via Zn foil interlayer alloying in FSW process of magnesium alloy

Abstract

The present study demonstrates the friction stir welding (FSW) process can be used as a mechanical alloying tool to fabricate a solid solution. An attempt has been taken for alloying the AM20 Mg base matrix using Zn at the weld zone during friction stir welding. Successful joints with sound mechanical properties and enhanced quality attributes are observed in the welds. Use of Zn alloying element at the nugget zone, the joint efficiency reached 90% to that of the base material and also which is about 25% more than the strength obtained in the case of without alloying element set of experiments. The addition of Zn alloy to Mg substrate forms Mg–Zn binary solid solution reinforcing intermetallic compounds, namely MgZn and Mg7Zn3 resulting in improved joint properties. This research work also reports the investigative outcomes, namely flow in the joint area, metallurgical deviation, microstructural modification, and diffusion of the constituent alloying element during the welding process. The targeted objective was effectively accomplished and the Zn alloyed stir area can fulfil the required application. The findings from the selective alloying process may be relevant for the implementation of industrial users over Mg alloys using a FSW process with better weldability and improved strength.