Laser welding of advanced high strength steels for fabrication of tailor welded blanks is of increasing interest for continued improvements in vehicle performance and safety without an increase in weight. Experimental results have shown that formability of welded dual-phase (DP) steels is significantly reduced by the formation of a softened region in the heat-affected zone (HAZ). In this study, a finite element simulation of welded DP980 samples undergoing transverse uniaxial tensile testing was used to evaluate the effects of soft zone width and strength on formability characteristics. Both the strength and the ductility of laser welded blanks decreased compared with those of unwelded blanks due to the formation of a softened outer-HAZ, where strain localization and final fracture occurred during tensile testing. The magnitude of softening and the width of the HAZ depend on the laser specific energy. It was observed from tensile test experiments and numerical simulations that both a decrease in strength and an increase in width of the softened HAZ were responsible for a decrease in the overall strength and ductility of the welded blanks.
The excellent pseudoelasticity, shape memory and biocompatibility of Nitinol has made it a leading candidate for various applications, including aerospace, micro-electronics and medical devices. Challenges associated with the welding Nitinol need to be resolved before its full potential in practical applications can be attained. The current study details the effects of process parameters on the mechanical and pseudoelastic properties of Ni-rich pulsed Nd:YAG laser welded Nitinol. The weld strength, pseudoelastic and cyclic loading properties for varying welding parameters are compared to those of the base metal. Furthermore, fracture surfaces have been analysed and detailed. Results show that process parameters greatly influence the mechanical performance and fracture mode of weldments.
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