Mg/Cu/Al接触反应钎焊工艺及元素扩散行为分析

采用铜中间层对镁合金与铝合金进行了接触反应钎焊，利用SEM，EDS研究了接头的微观形貌及组织结构，并对界面Cu元素的扩散行为进行了分析. 结果表明，铜中间层可有效阻隔镁与铝的接触反应，界面无Mg-Al系金属间化合物生成；相同温度下，Cu原子在Mg元素中的扩散能力远大于在铝中的扩散能力，导致Al/Cu侧在温度低于560 ℃时无法产生有效连接，且温度高于570 ℃时镁合金溶解过多，工艺区间过窄. 在565 ℃保温20 min可实现连接，但抗剪强度仅12.6 MPa. 采用低温长时间保温，随后高温短时加热的工艺可实现Mg/Cu/Al接头有效连接. 在475 ℃保温60 min,560 ℃加热7 min的条件下，接头强度可达31.2 MPa.

Process and diffusion analysis on contact reactive brazing of Mg/Cu/Al

Mg alloy and Al alloy were contact-reaction brazed using an intermediate layer of Cu. The joint morphology and interfacial structure were characterized by SEM and EDS, and the diffusion behavior of Cu element was analyzed. It was found that Cu interlayer could effectively block the Mg and Al contact reaction during the joining, thus avoiding the formation of Mg-Al intermetallic compounds. At the same temperature, the diffusion coefficient of Cu element in Mg alloy is much higher than that in Al alloy, which made the Al/Cu interface cannot achieve effective connection below 560 ℃ and Mg alloy many losses occur when temperature is higher than 570 ℃. The applicable range of process parameters was narrow. Mg/Cu/Al contact reaction could be achieved effetely heating at 565 ℃ for 20 min, but the shear strength of joint was only 12.6 MPa. Sound Mg/Cu/Al joint could be obtained under the condition of long-time heating at low temperature firstly and short-time heating at high temperature later. The joint, which was obtained at 475 ℃ for 60 min and then 560 ℃ for 7 min, had a relatively high shear strength of 31.2 MPa.