激光焊接铜与不锈钢接头之间焊缝区显微组织的非均匀性（英文）

An insight into microstructural heterogeneities formation between weld subregions of laser welded copper to stainless steel joints

研究激光焊接(LBW)工艺对铜(Cu)和不锈钢(SS)异种焊缝显微组织与力学性能关系的影响。采用背散射(BSE)扫描电子显微镜(SEM)成像来表征LBW (Cu-SS)焊缝的高度非均匀组织特征。BSE分析充分证明在异种焊接界面和熔合区产生复杂的显微组织。沿铜/焊缝界面存在明显的晶粒生长差异:从粗柱状晶到等轴状超细晶。高分辨电子背散射衍射(EBSD)分析证实铜/焊缝界面存在晶粒细化机制。拉伸和冲击试验结果表明,异种焊缝的拉伸和冲击性能与铜基体的基本一致。在熔合区和铜/焊接界面区等非均匀材料成分区,存在明显的显微硬度梯度。为了全面了解局部焊缝亚区的组织与性能的关系,确定出焊缝亚区的异质形核点,并与显微硬度测试结果相互关联。

The effect of laser beam welding(LBW) process on the microstructure-mechanical property relationship of a dissimilar weld between the copper(Cu) and stainless steel(SS) was investigated.Backscattered electron(BSE) based scanning electron microscopy(SEM) imaging was used to characterize the highly heterogeneous microstructural features across the LBW(Cu-SS) weld.The BSE analysis thoroughly evidenced the complex microstructures produced at dissimilar weld interfaces and fusion zone along with the compositional information.Widely different grain growths from coarse columnar grains to equiaxed ultrafine grains were also evident along the Cu-weld interface.A highresolution electron backscattered diffraction(EBSD) analysis confirmed the existence of the grain refinement mechanism at the Cu-weld interface.Both tensile and impact properties of the dissimilar weld were found to be closely aligned with the property of Cu base metal.Microhardness gradients were spatially evident in the non-homogeneous material composition zones such as fusion zone and the Cu-weld interface regions.The heterogeneous nucleation spots across the weld sub-regions were clearly identified and interlinked with their microhardness measurements for a holistic understanding of structure-property relationships of the local weld sub-regions.The findings were effectively correlated to achieve an insight into the local microstructural gradients across the weld.