No abstract

No abstract

No abstract

No abstract

No abstract

Ni-based filler metal and Ni-Cu-based filler metal were used to obtain copper/stainless steel (Cu/SS) joints through wire-feeding laser welding. Along the SS/weld interface, there exist different grain sizes (from coarse columnar grains to fine equiaxed grains). The heat affected zone (HAZ) on the copper side consisted of two areas with different grain sizes and the size of the grain in the Cu-HAZ of the Ni-Cu-based filled joint was much smaller than that of the Ni-based filled joint. Our results showed that grain refinement at the copper/weld (Cu/weld) interface of the Ni-Cu-based filled joint was observed through high-resolution electron backscattered diffraction (EBSD). There was a hardness elevation at the Cu/weld interface of the Ni-Cu-based filled joint due to the grain refinement on the weld of the copper side. The maximum tensile strength of the Ni-Cu-based filled joint was obtained and reached 91.2% of the tensile strength of the copper base metal (Cu-BM). Joints in this study were observed to fracture in a ductile mode. Furthermore, the Ni-Cu-based filled joint exhibited a higher plastic deformation, which was primarily caused by the large deformation of the weld zone and the large deformation of the Cu-BM due to the high plasticity of the weld, which alleviated the stress concentration, as indicated by 2D-digital image correlation (DIC) test results.

No abstract

In this paper, ultrasonic C-scan detection is conducted on stainless steel spot welds, and C-scan images are obtained respectively through characteristic signal analysis in time domain and frequency domain. Cscan image of frequency domain characteristics signal, which is less affected by detecting conditions, can reflect the weld nugget morphology more truly. After C-scan image enhancement and edge detection processing, the dimension of spot weld nugget can be automatically obtained through equivalent diameter algorithm procedure. The dimension of nugget contains corona bond, and it is in good agreement with corona bond external diameter through metallographic measured value. So it can be taken as the reference to evaluate the quality of spot welds. Without the influence of corona bond, detection accuracy is very high. The error is less than 0.066 mm.