Papers by Author: Bo Qiang Li

Abstract: Dissimilar metal of Steel and Magnesium alloy used for friction stir spot welding is studied. Based on using orthogonal test method optimizes the process parameters and gets satisfactory joints , SEM is used to observe the features of joint,XRD is applied to determine the joint phase, and the results show that: the design of rotating tool without pin is reasonable and it can form satisfactory joints without keyhole of spot welding. The performance of spot welding joint depends on the extent of diffusion of Zn and Mg and high weld consistency. There is small existence of intermetallics made of MgZn2,Mg0.97Zn0.03 in welding joint.The properties of joint depends on the intermetallics, Due to this,The microhardness of joint increases gradually from the magnesium side to steel side.

Abstract: Dissimilar metal of Steel and Magnesium alloy by friction stir spot welding is studied. Based on using orthogonal test method to optimize the process parameters and get satisfactory joint, SEM is used to observe the features of joint, fracture morphology, and XRD is used to determine the joint phase, and the results show that: the design of rotating tool without pin is reasonable and it can form satisfactory joints without keyhole for spot welding; spot welding nugget zone on the magnesium side shows the phenomenon of melting and solidification in the range of hundreds microns, and its microstructure appears a structure of dendrites; The fracture mode of spot welding joint is a mixed mode of cleavage and dimpled rupture.

Abstract: The Friction stir blind riveting (FSBR) process consists of a blind rivet is driven at high rotational speed and brought into contact with the workpieces, thereby generating frictional heat between the rivet and the workpiece, which softens the workpiece material and enables the rivet to be driven into the workpieces under reduced force. The riveting of lap joint of AZ31B(3mm) magnesium alloys plate and a DP600 (1mm) high strength steel plate was produced by FSBR using 2200rpm rotation speed, various feet rates and different lap mode to investigate the effects of the joint morphology and strength. The joint strength depended strongly on the shank of rivet itself shear strength，however in which case the strength of joint impacted by rivet assembly quality (the lap of plates, the tightness rivet of workpiece). So positioning the steel sheet on the top is desirable, the maximum shear strength of the joint reached about 6.0KN.