微焊点纳米压痕循环力学行为与承受载荷的关联性

通过对Sn-3.0Ag-0.5Cu/Cu和Sn-0.3Ag-0.7Cu/Cu微焊点进行循环加载-卸载方式的纳米压痕试验,研究了焊点循环力学行为与承受最大载荷的关联性.结果表明,循环F-h曲线在闭合前表现为1个迟滞回环,随着最大载荷的增加,焊点迟滞回环的面积和残余压痕深度增大;当最大载荷一定时,迟滞回环的面积及残余压痕深度增量随着加载次数的增加逐渐减小;微焊点的压痕蠕变C随最大载荷的增大而不断降低,同时随加载次数的增加先急剧减小而后逐渐趋于平稳.Sn-3.0Ag-0.5Cu/Cu焊点的压痕蠕变低于Sn-0.3Ag-0.7Cu/Cu焊点的蠕变量.

Effect of maximum loading on cycling mechanics behavior of micro-soldered joints by nanoindentation method

Microstructures of laser-welded Cu-Al joint are different from that made by other welding methods due to the rapid heating and solidification during laser welding process,which produces the high temperature and constituent gradient in the welding pool.In present paper,laser lap welding of copper and aluminum,tensile shear testing,examinations of weld joint cross-section and fracture surface using SEM & EDS were carried out to study the microstructural characteristics of laser-welded Cu-Al joint and the effects of microstructure on the joint mechanical properties.The results show that diverse microstructures were formed in the joint under the conditions of high temperature and constituent gradient due to the high solidification rate of laser welding process.Several different zones were identified in this study.They are band shape hypereutectic with the characteristic of parallel arrangement,mixed structures of hypereutectic and eutectic (mixed zone for short),lamellar eutectic and dendritic hypoeutectic.The results of tensile testing and fracture surface analysis indicate that the defect occurred in the mixed zone of hy- pereutectic and eutectic structure.With the increase of welding speed,mixed zone width decreased and the hypereutectic morphology transited from the equiaxed shape to band shape.Meanwhile, the maximum shear strength of the weld joint increased with increasing of welding speed.