Partially Melted Zone in Dissimilar Aluminium Alloy Welds-Effect of Prior Thermal Temper and Welding Process

Partially melted zone (PMZ) of aluminium alloy welds is an important region and requires careful attention. This is mainly because PMZ in these alloys is a weak link in the weldments and is significantly affected by welding parameters. Microstructural changes in PMZ are related not only to welding heat input and processes, but also depend on the initial thermal history of the alloy (for example, whether it is in O, T4, T6 orT87 condition etc.). Interestingly not many detailed studies are available in this respect. In the present work effect of prior thermal temper and welding process on the PMZ behaviour of dissimilar AA2014 and AA6061 alloy GTA and EB welds were studied. Grain coarsening and melting in PMZ is more when the alloys are welded in T4 temper than in O condition and AA2014 alloy is prone for liquation compared to AA6061 alloy which attributes high alloying element concentration in AA2014 side of the joint. EB welding proved to be efficient welding process compared to GTA welding in terms of resistance to liquation and better mechanical properties.