Hybrid Laser/GMA Welding Aluminium Alloy 7075
Aluminium alloy 7075 is a heat treatable alloy based on Al-Mg-Zn system (5–6 wt % Zn, 2–3 wt % Mg and 1–2 wt % Cu) with the high strength obtained by precipitation hardening treatment. This alloy has the characteristics of a high thermal sensitivity and a low eutectic liquidus temperature range, which make it difficult to weld. The severe HAZ softening, the cracking in the weld and the material lose by vaporisation are the major problems encountered during fusion welding. In this study, the weldability of AA 7075 (T6) sheet using the hybrid laser/GMA welding process was examined. The hybrid welding set-up comprised a 3 kW Nd:YAG laser and a pulsed GMA welding machine. Both bead-on-plate welding and butt-welding were performed under various conditions. The results indicate that hybrid laser/GMA welding process at the optimised conditions can successfully fusion weld AA 7075. The welds produced by the hybrid welding process have a similar HAZ width as the weld produced by autogenous laser welding. Whereas the hybrid process overcomes the problem of severe top bead undercut created in autogenous laser welding. Transverse solidification cracking, however, was found to appear when the arc power was higher than a certain level. Below the level the welds produced were cracks free. Careful thermocouple measurements of the temperature profile in the workpiece were carried out during the welding. The temperature isotherms show that the solidification cracking was related to the elongation of the mushy zone formed in the high speed welding process.
IIW-Thesaurus keywordsGMA welding Arc welding Gas shielded arc welding Laser welding Photon beam welding Radiation welding YAG lasers Lasers Combined processes Aluminium alloys Light metals Weldability Solidification cracking Cracking Defects Hot cracking Reference lists
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