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Microstructures and Mechanical Properties of Regular and Titanium Powder Filled Fibre Laser Lap Welded Dual-phase (DP) Steel
L-R. Yin, B-Y. Wu, H. Qu and J. Zhang

To study the microstructures and mechanical properties of the welded joints of a dual-phase (DP) steel after laser lap welding, we performed the laser lap welding and laser powder filling with titanium powder lap welding of DP590 steel using a fiber laser with optimized welding parameters. The experimental results show that the microstructures of seam region of DP590 steel are mainly composed of martensite. There exists a softening zone in the weld joints, which is mainly originated from the generation of tempered martensite due to the thermal effect during laser welding. The hardness and yield strength of weld seam region for the welding specimens filled with titanium powder are both decreased, while the shear strength is increased relative to the unfilled ones. Analysis of shear fracture morphology shows that the welded joints of powder-filled specimen exhibit obvious ductile fracture, and they have the better toughness and ductility as compared with the unfilled ones.

Keywords: Fibre laser, DP590, dual-phase (DP) steel, titanium powder, laser lap welding, welding joint, microstructure, mechanical property, hardness, yield strength, shear strength

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