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Laser Welding of Steel Laminates: Measurement of Elastic Modulus with Three-point Bending
N. Abu-Dheir and B.S. Yilbas

Laser welding offers considerable advantages over the conventional welding techniques such as precision of operation, high speed welding, and small heat affected zone. Laser welding also provide improved mechanical and metallurgical properties of the weld section, due to localized high intensity heating, as compared to those produced by the conventional techniques. Although the process is fast, the high cooling rates may results in hot spots in the weld section, especially when oxide compounds are presents. In this case, the release of oxygen and other carbonic gases in the weld section are responsible for the formation of the hot spots in this region. Consequently, it is necessary to investigate into some of the mechanical properties, such as the elastic modulus and hardness, of the weld sections. In the present study, laser welding of steel sheets is carries out at different combinations of laser welding parameters. The elastic modulus of the weld section is obtained through the three-point bending tests. The hardness across the weld section is measured using microindentation testing. The heat affected zone (HAZ) of the welds resulted is assessed after incorporating the optical and scanning electron microscopes. The oxide compounds formed in the weld section are also analysed using X-ray diffraction (XRD). It was found that the laser produced weld sections have lower elastic modules than the base material, provided that some small variation in the elastic modulus for the weld sections are observed when the welding parameters are changed. The hardness profile across the weld cross-section and the optical photographs reveal that the HAZ is considerably narrow.

Keywords: Laser butt welding, three-point bending, elastic modulus, microstructure, heat affected zone (HAZ), hardness profile

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