Microstructure and mechanical properties of pulse VPPA welded high-strength aluminum alloy joints

The 7075 aluminum alloy sheet with thickness of 10mm was welded by pulse VPPA vertical welding process, the microstructures and mechanical properties of welded joint were studied by means of optical microscope(OM), scanning electron microscope(SEM), X-ray diffraction(XRD), universal tensile testing machine and micro-hardness testing machine. The effect of pulse on microstructure and mechanical properties of welded joint were comparatively investigated. Experimental results indicated that the finally welded products exhibited an excellent appearance. Due to the enhanced stirring effect in weld pool induced by the periodicity variation of pulse current, the microstructure and the strengthening T phase of the weld were refined, the tensile strength and the hardness of the welded joint were increased. The tensile strength reached 397.9 MPa, which was nearly 67.5% of the parent metal, and it was increased by 5.13% than the weld without pulse treatment, the welding quality was also improved.