DOI: 10.3724/SP.J.1037.2013.00341

Acta Metallurgica Sinica (金属学报) 2013/49:12 PP.1493-1500


Dual phase (DP) steels have good combinations of strength and ductility, and are being increasingly used in vehicle body structures to meet enhanced government regulations and safety standards. The use of DP steels in automotive industries involves laser welding, which would lead to changes in local material properties and create potential safety and reliability issues under dy- namic loads. The present work aimed to study the effects of strain rate on tensile properties and deformation behavior of laser welded DP780 steel joints. The results showed that the deformation behavior of laser welded joints was more sensitive to strain rate as compared to base metal of DP780 steel. The strength of DP780 steel joint increased with increasing strain rate, while the ductility de-creased first with increasing strain rate from 10-3to101s-1, and then increased up to a strain rate of 102 s-1. The strain rate sensitivity of the deformation behavior of DP780 steel joints was mainly dependent on the change of deformation behavior and its mechanisms of base metal at various strain rates. The distance of the tensile failure location from the weld centerline decreased obviously with the increase of strain rate. And the failure location changed from the base metal to the softened heat-affected zone (HAZ) as strain rate increased. The mechanism for changing failure location can be related to the strain rate dependence of the plastic deformation behaviors of microstructures in various regions across a joint.

Key words:laser welding,dual phase steel,dynamic load,strain rate,deformation behavior

ReleaseDate:2015-03-06 17:46:58

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