The wetting of galvanized steel by molten Al alloys was studied in the cold metal transfer process by the sessile drop method using a high speed video camera.The wetting behavior can be divided into two typical cases,trending of non-wetting by using small wire feeding speed and wetting by using large wire feeding speed.The Leidenfrost effect is caused by the volatilization of Zn,which is responsible for the former case.The enhanced wettability of steel by Al and the weakening of the Leidenfrost effect are responsible for the latter case.Zn is the destabilizing factor for Al-steel joining that needs to be avoided by a reasonable design of process.
采用冷金属过渡(Cold metal transfer,CMT)技术,以镍铝青铜ERCuNiAl焊丝作为填充材料,对钛合金Ti6Al4V和纯铜T2异种金属薄板进行钛板在上铜板在下的搭接连接。使用扫描电镜和能谱分析研究焊接接头的显微组织和反应界面金属间化合物的组成,并通过横向拉伸试验对接头的力学性能进行评定。研究结果表明,冷金属过渡技术可以实现于钛/铜异种金属的有效连接。焊接过程中电弧比较稳定,焊缝成形良好。在电弧热的作用下,铜板完全熔透,与焊缝金属形成铜-焊缝界面,钛板部分熔化,铜板和焊丝熔化包围在钛板的周围,形成了钛和焊缝的三个界面,提高了接头的力学性能。钛侧金属间化合物层包含TiCu、TiAl、Ti2Cu、AlCu2Ti和铜基固溶体等多种金属间化合物。拉伸试验时,断裂发生在铜母材的热影响区,拉剪强度可达200 MPa。
