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朱元皓, 董红刚, 吴宝生, 郭柏征, 李鹏. 液相分离对T2紫铜/316L不锈钢接头组织及性能的影响[J]. 焊接学报, 2021, 42(11): 14-21. DOI: 10.12073/j.hjxb.20210506002
引用本文: 朱元皓, 董红刚, 吴宝生, 郭柏征, 李鹏. 液相分离对T2紫铜/316L不锈钢接头组织及性能的影响[J]. 焊接学报, 2021, 42(11): 14-21. DOI: 10.12073/j.hjxb.20210506002
ZHU Yuanhao, DONG Honggang, WU Baosheng, GUO Baizheng, LI Peng. Effect of liquid phase separation on microstructure and properties of T2 copper/316L stainless steel joint[J]. TRANSACTIONS OF THE CHINA WELDING INSTITUTION, 2021, 42(11): 14-21. DOI: 10.12073/j.hjxb.20210506002
Citation: ZHU Yuanhao, DONG Honggang, WU Baosheng, GUO Baizheng, LI Peng. Effect of liquid phase separation on microstructure and properties of T2 copper/316L stainless steel joint[J]. TRANSACTIONS OF THE CHINA WELDING INSTITUTION, 2021, 42(11): 14-21. DOI: 10.12073/j.hjxb.20210506002

液相分离对T2紫铜/316L不锈钢接头组织及性能的影响

Effect of liquid phase separation on microstructure and properties of T2 copper/316L stainless steel joint

  • 摘要: 采用钨极氩弧焊填充纯铜焊丝进行T2紫铜/316L不锈钢异种金属焊接工艺试验,分析了接头微观组织的形成机制. 结果表明,使用纯铜焊丝时,铁-铜液相分离对铜/钢焊缝组织的形成起主导作用. 以铜为基体的焊缝中分布着大量由铁-铜初次液相分离形成的富铁球,在其内部还分布有标志着铁-铜二次液相分离的富铜相. 富铁球内的析出相在表面能梯度和密度差的作用下,向富铁球中心呈球状聚集. 由于成分和所处区域的冷却速率不同,富铁球呈现不同的形貌. 基于熔池边界凝固理论,分析了接头铜/钢界面未混溶区宏观偏析机制. 填丝焊时,熔池边缘形成非等温边界. 纯铜焊丝制备接头铜/钢界面处液态钢母材的温度高于熔池主体,导致岛状和半未混溶区的形成. 接头的铜侧存在由粗大晶粒和正常尺寸晶粒组成的软化区,拉伸试样均断裂于此,抗拉强度达到铜母材的81.7%.

     

    Abstract: Dissimilar T2 copper/316L stainless steel joints without defects were prepared by gas tungsten arc welding with Cu filler wire. Microstructure evolution and mechanical properties the joints were investigated. When Cu filler wire was used, the microstructure of copper/steel weld was largely affected by liquid phase separation between iron and copper. Fe-rich spherulites produced by primary liquid phase separation distributed in Cu-based weld. Inside the Fe-rich spherulites, minority Cu-rich spheres formed by secondary liquid phase separation. During solidification, the internal precipitated phases migrated to the center of Fe-rich spherulites due to the interface energy gradient and density difference. The Fe-rich spherulites presented different morphologies because of the differences in composition and cooling rate. The macro-segregation mechanism of melted unmixed zone near fusion boundary was studied based on solidification theory of fusion-boundary. When copper filler wire was used, non-isothermal pool boundary formed at fusion boundaries. The liquidus temperature of bulk weld pool is lower than that of steel base metal in joint. Resultantly, a bulk molten pool cooler than the melted 316L base metal formed near the solidification front. Subsequently, the melted unmixed BM was carried into the cooler molten pool by the convection and agitation, and solidified quickly into a peninsula and island shape before it fully mixed with the bulk weld pool. A softened zone existed in the copper sheet, which consisted of zones with different grain sizes. All tensile specimens fractured at HAZ on the copper side with a ductile fracture mode, and the maximum strength reached 81.7% that of Cu base metal.

     

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