Modelling of work-hardening behaviour for laser welded magnesium alloy

To investigate the reliability of the laser welding process for the magnesium alloy ZE41A-T5, eight butt joints were welded using the same processing parameters. These joints were tensile tested in the as-welded and aged conditions and the tensile data were analyzed from work-hardening characteristics. The flow curves cannot entirely be satisfactorily described by the Kocks-Mecking model; however, the model is still applicable to the high strain zone of the flow curves where work-hardening rate decreases linearly with flow stress. The reproducibility of the initial work-hardening rate and saturation stress is statistically analyzed. The initial work-hardening rates for the base castings and welded joints vary from approximately 4000 to 7000 MPa, i.e. 1/4 to 1/3 of the base material shear modulus. The as-welded joints have slightly higher initial work-hardening rates than the base castings. Artificial aging produces lower initial work-hardening rates compared with the base material. The saturation stress ranges approximately from 260 to 320 MPa, i.e. about 2% of the shear modulus. The saturation stress for the welded joints is lower than that for the base material. Compared with the as-weld joints, aging decreases initial work-hardening rate but slightly increases saturation stress. Both initial work-hardening rate and saturation stress become more scattered after aging.