# Study of the Influence of Gas Tungsten Arc (GTA) Welding on the Microstructure and Properties of Mg–Al–RE-Type Magnesium Alloys

## TL;DR

This study examines how gas tungsten arc welding affects the microstructure and hardness of two magnesium alloys containing rare earth elements.

## Contribution

The paper presents new insights into the microstructural changes and increased microhardness in Mg–Al–RE alloys after GTA welding.

## Key findings

- GTA welding significantly reduced the dendrite arm spacing by about 75% in the fusion zones of the alloys.
- The microhardness of the alloys increased by approximately 21% due to structural refinement from welding.
- The phase composition remained consistent before and after welding in both alloys.

## Abstract

The effects of the gas tungsten arc (GTA) welding process on the microstructure and microhardness of two Mg-5Al-3RE and Mg-5Al-5RE experimental alloys (RE—rare earth elements) are presented. Both alloys were gravity-cast in a steel mould and GTA-welded in the same conditions. Analyses of the alloys’ microstructure were carried out by scanning electron microscopy (SEM+EDX) as well as X-ray diffraction (XRD). In as-cast conditions; both alloys were mainly composed of α-Mg; Al11RE3; and Al10RE2Mn7 intermetallic phases. Additionally; α+γ eutectic (where γ is Al12Mg17) in the Mg-5Al-3RE alloy and an Al2RE phase in the Mg-5Al-5RE material were revealed. The same phase composition was revealed for both alloys after the GTA welding process. The results of the dendrite arm size (DAS) and Vickers microhardness measurements were also described. Both welded materials exhibited an intensive size reduction of the structural constituents after GTA welding. About 75% smaller values of the dendrite arm spacing were revealed in the fusion zones of the investigated materials than in the as-cast conditions. The GTA welding process also influenced the microhardness of the experimental alloys and increased them by about 21% compared to the base metal; which was the consequence of the refinement of the structural constituents.