Heterogeneous structure-induced strength and ductility synergy of α-brass subjected to rapid cooling friction stir welding  

异质结构改善α-黄铜快速冷却搅拌摩擦焊缝的强塑性

作　　者：Nan XU Lei CHEN Bo-kun GU Zi-ke REN Qi-ning SONG Ye-feng BAO 许楠;陈磊;顾帛坤;任紫科;宋亓宁;包晔峰(河海大学机电工程学院,常州213022)

机构地区：[1]College of Mechanical and Electrical Engineering,Hohai University,Changzhou 213022,China

出　　处：《Transactions of Nonferrous Metals Society of China》2021年第12期3785-3799,共15页中国有色金属学报（英文版）

基　　金：The authors are grateful for the financial supports from the Natural Science Foundation of Jiangsu Province,China(No.BK20211067);the National Natural Science Foundation of China(No.51805145);the Changzhou Science and Technology Program,China(No.CJ20200076);the Fundamental Research Funds for the Central Universities,China(No.B200202229);the‘Blue Project’of Jiangsu Province,China.

摘　　要：The 2 mm-thickα-brass plates were successfully joined using conventional friction stir welding(CFSW)with air cooling and rapid cooling friction stir welding(RCFSW)with liquid CO2 cooling.The microstructure and mechanical properties of the two welds were carefully investigated by electron back-scattered diffraction and transmission electron microscopy.The stir zone of CFSW exhibited homogeneous equiaxed grains,while the stir zone of RCFSW showed a heterogeneous grain structure,i.e.ultrafine grains containing massive dislocations and nano twins.Compared with the CFSW,yield strength and ultimate tensile strength of RCFSW were increased by 31%and 24%,respectively.The enhanced yield strength and improved strain hardening capacity were attributed to grain boundary strengthening and dislocation strengthening.Furthermore,good ductility was achieved due to the released stress concentration of the nano twins caused by the plastic deformation.采用传统搅拌摩擦焊(空冷)和快速冷却搅拌摩擦焊(液态二氧化碳)成功焊接2 mm厚的α-黄铜薄板。利用电子背散射衍射和透射电子显微术对焊缝的显微组织和力学性能进行研究。结果表明:传统搅拌摩擦焊缝为均匀等轴晶组织,而快速冷却搅拌摩擦焊缝呈现出含有大量位错和纳米孪晶的异质晶结构。快速冷却搅拌摩擦焊缝的屈服强度和抗拉强度较传统搅拌摩擦焊分别提高31%和24%。屈服强度和应变硬化能力的改善归因于晶界强化和位错强化,同时,纳米孪晶可缓解塑性变形引起的应力集中,使焊缝表现出良好的塑性。

关 键 词：friction stir welding BRASS microstructure RECRYSTALLIZATION mechanical properties 

分 类 号：TG453.9[金属学及工艺—焊接]