Microstructure and Corrosion Properties of the Plasma-MIG Welded AA5754 Automotive Alloy

A Abouarkoub,G Scamans,G E Thompson,X Zhou

doi:10.4236/jmmce.2015.34034

A Abouarkoub, G Scamans + Show 2 more

Open Access

https://doi.org/10.4236/jmmce.2015.34034

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Abstract

The influence of heating cycles during plasma metal inert gas (MIG) welding on the microstructure and corrosion properties of the AA5754 automotive alloy has been investigated. The high heat input during plasma-MIG welding results in a significant modification in the microstructure of the AA5754 alloy adjacent to the fusion boundaries. As a consequence of partial melting of the Al-Fe-Mn-(Si) intermetallics at the partially melted zone (PMZ) and segregation of the high melting point elements (particularly Fe and Mn) toward the fusion zone, severe galvanic corrosion attacks can be enhanced along the PMZ of the AA5754 weld during exposure to aqueous corrosion environments.

Highlights

In the automotive industry, welding is one of the most critical elements of the body assembly process, which determines the structural integrity and quality of the vehicles being manufactured
The microstructure of the automotive aluminium wrought alloys can be significantly modified by the high heat input employed during fusion welding techniques, such as the plasma metal inert gas (MIG) welding [1]-[3]
One of the most critical defects induced by fusion welding, which may contribute to the loss of mechanical and corrosion properties, is the inhomogeneity near the fusion boundary

Summary

Introduction

In the automotive industry, welding is one of the most critical elements of the body assembly process, which determines the structural integrity and quality of the vehicles being manufactured. The composition gradients through the base metal, partially melted zones and the fusion zone of the commercial 5xxx alloys, such as AA5754, are often caused by the rejection of high melting point impurities, for example iron and manganese, from the newly forming solid weld metal into the melt during the initial stage of solidification. This phenomenon, in turn, is expected to modify the corrosion behaviours and, the overall performance of these alloys during service

Experimental

Microstructure Characterization of the AA5754 Plasma-MIG Weld

Corrosion Assessment of the AA5754 Plasma-MIG Weld

Conclusion