科研之友
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摘要
Dissimilar joints of DP600-DP980 were made by fiber laser welding with a focused and defocused beam. The defocused laser intensified the hardness drop of the softened heat affected zone (HAZ), whereas the hardness of the fusion zone was essentially unaffected. The joint by the defocused beam exhibited tensile behavior similar to that of the joint by the focused beam except for a slightly increased yield strength. All of the joints presented a higher yield strength and lower ductility than that of the corresponding base metal. The numerically simulated load-displacement curves of the DP600-DP980 joints exhibited reasonable agreement with the experimental data. The strain firstly localized in the softened zone of the DP600 side due to its lower hardness. The hardened fusion zone constrained the plastic deformation of the softened zone and resulted in biaxial stress state. The effective stress of the softened HAZ at the DP600 side was lower than that of DP600, and necking occurred in DP600. The failure location depended on the HAZ softening effect associated with the stress intensification effect.
