Transport phenomena in conduction mode laser beam welding of Fe-Al dissimilar couple with Ta diffusion barrier

Abstract

Fusion welding of dissimilar metals always encounters immense difficulties due to the formation of brittle intermetallic phases that make the joint unsuitable for structural applications. Using a barrier layer that wets well with either component but does not undergo melting itself and prevents intermixing and undesirable phase formation could be a possible remedy. In order to explore this hypothesis, we have made an attempt to numerically simulate and experimentally validate the heat and mass transport phenomena in the fusion zone concerning laser assisted welding of Fe-Al dissimilar couples with 0.2 mm Ta foil as the diffusion barrier butted between Fe and Al. The results suggest that the Fe-side undergoes greater degree of melting resulting in an asymmetric thermal and velocity fields. Furthermore, partial melting of Ta seems unavoidable but proves benign as this leads to good bonding between Fe-Ta and Ta-Al while precluding formation of Fe-Al alloy/intermetallic phases.