镁合金具有比强度、比模量高，密度低、制造成本低、散热性好，阻尼减振降噪能力强、能屏蔽电磁辐射等优点而日益受到重视，但镁合金在高温条件下的力学性能、耐腐蚀性能等不佳很大程度的限制了其应用。由于钛合金具有高的比强度、耐热与耐蚀性好、断裂韧性强等特点，而在航空航天、地质勘探等领域得到重用。为了发挥镁钛异种金属各自的性能优势，进一步扩大镁合金作为结构件在高新技术领域的应用，很有必要将镁合金与钛合金连接起来获得界面结合牢固的焊接接头,这样既可以降低结构重量又可以节约材料。 本文以探索镁-钛异种材料的焊接性能为目的，采用纯Ni箔、Cu箔、Al箔为中间层材料，进行了AZ31B镁合金/Ti-6Al-4V钛合金的瞬间液相扩散连接试验研究，利用金相显微镜、扫描电子显微镜(SEM)、能谱分析(EDS)、显微硬度计、强度分析等测试方法，研究了不同中间层材料及焊接工艺参数与焊接接头微观组织结构、元素行为、接头力学性能等之间的关系，确定最佳工艺参数范围，探讨接头形成机理，以获得理想的镁-钛异种材料瞬间液相扩散连接接头。 研究结果表明，采用纯Ni箔、Cu箔、Al箔为中间层材料，在焊接温度520℃~540℃、保温时间5min~30min的条件下均可实现AZ31B镁合金与Ti-6Al-4V钛合金的冶金结合。以Ni箔为中间层的AZ31B/Ti-6Al-4V接头的界面扩散区呈层状结构分布，由镁合金侧至钛合金侧的显微组织依次为：α-Mg固溶体、(α-Mg+Mg-Al-Ni)共晶组织、Mg- Al-Ni三元金属间化合物、Ti3Al化合物，Ti(Mg,Al)固溶体及少量Mg17Al12。扩散区硬度从钛侧至镁侧呈不断减小趋势，520℃、10min时的接头显微硬度达到最大，约为330.09HV。接头的剪切强度随保温时间的延长呈先增大后减小的趋势，520℃、10 min的接头剪切强度值达到最大61 MPa，约为AZ31B母材的43%。接头的剪切断裂面位于钛/镍界面附近，断口呈韧-脆混合断裂。 以Cu箔为中间层的AZ31B/Ti-6Al-4V接头显微组织从Ti-6Al-4V侧向AZ31B侧依次为：γ-Cu固溶体，Cu3Ti、Cu2Al化合物，Mg-Cu-Al三元金属间化合物，Mg17(Cu,Al)12及(α-Mg+Mg2Cu)共晶组织。接头硬度从钛侧至镁侧呈先减小后增大最后再减小的趋势，520℃、20min时的接头显微硬度值最大，为292.87HV。接头的剪切强度随保温时间的增加呈先上升后趋于平缓的规律，520℃、20 min的接头剪切强度达到最大值69 MPa，约为AZ31B母材的49%。接头沿铜/镁界面发生剪切断裂，断口呈韧-脆混合断裂。 以Al箔为中间层的AZ31B/Ti-6Al-4V接头显微组织从钛侧到镁侧的显微组织依次是：α-Ti固溶体、Ti3Al化合物，(α-Mg+Mg2Al)共晶组织及少量Mg17Al12化合物。接头显微硬度呈阶梯状下降趋势，540℃、10min时的显微硬度最大，为306.87HV。接头的剪切强度随保温时间的延长呈先增大后减小的规律，540℃、20min的接头剪切强度达到最大值71MPa。接头剪切断裂沿钛/铝界面发生，断口韧窝明显。

Magnesium alloys have the properties of high specific strength, high specific modulus, low density, low manufacturing costs, good heat dissipation, good damping shock resistance, good electromagnetic shielding and so on. More and more people pay attention to magnesium alloys. However, the bad mechanical properties at high temperature and low corrosion resistance limit the application of magnesium alloys. Because of its high specific strength,good heat resistance and corrosion resistance, high fracture toughness and so on,titanium alloys can be used in the field of aerospace and geological exploration. In order to make full use of dissimilar metals’ performance advantage, to expand the application of magnesium alloys as the structure parts in the field of high technology, it is necessary to connect the magnesium alloys and titanium alloys to get interfacial bonding firm weld joints, which can reduce the structure weight and save materials. In this paper, the purpose of research is to explore the welding properties of magnesium- titanium dissimilar materials (AZ31B/Ti-6Al-4V) by transient liquid phase bonding (TLP). High purity Ni foil,Cu foil and Al foil were selected as intermediate layer. Microstructure, element behavior and mechanical properties with different intermediate layer materials and technology parameters were analyzed by means of optical microscope, scanning electron microscope (SEM) accompanied by EDS, microhardness and strength analyzer. The good welded joint status was obtained by the optimization of the technological parameter. The results show that: Good surface welding joint can be got under porper brazing parameter (bonding temperature is 520℃~540℃, holding time is 5min~30min) by Ni, Cu or Al foil as intermediate layer. The microstructure from magnesium side to titanium side at interface zone of AZ31B/Ni/Ti-6Al-4V diffusion brazing joint includes α-Mg solid solution, (α-Mg+Mg-Al-Ni) eutectic structure, Mg-Al-Ni ternary intermetallic compounds, Ti3Al intermetallic compounds Ti(Mg,Al) solid solution, and small amount of Mg17Al12. The microhardness from Ti-6Al-4V side to AZ31B side decreases continuously. When the welding temperature was 520℃ and the holding time was 10min, the microhardness of the joint reached the maximum, about 330.09HV.As the welding temperature increases, the shear strength shows an increasing trend at first and then decreases. When the welding process is 520℃ keeping for 10min, the highest shearing strength of the joint can reach 61Mpa, which reaches approximately 43% AZ31B magnesium alloy. Welding joint cracks along Ti/Ni interface, and the surface is ductile-brittle hybrid fracture. Good surface welding joint can be got under porper brazing parameter by Cu foil as intermediate layer. The microstructure from Ti-6Al-4V side to AZ31B side at interface zone of diffusion brazing joint includes γ-Cu solid solution, Cu3Ti, Cu2Al, Mg-Cu-Al ternary intermetallic compounds, Mg17(Cu,Al)12 and (α-Mg+Mg2Cu) eutectic structure. The microhardness from Ti-6Al-4V side to AZ31B side first increases and then decreases. When the welding temperature was 520℃ and the holding time was 20min, the microhardness of the joint reached the maximum, about 292.87HV. As the welding temperature increases, the shear strength shows an decreasing trend at first, then increasing and finally tends to decrease. When the welding process is 520℃ keeping for 20min, the highest shearing strength of the joint can reach 69Mpa, which reaches approximately 49% AZ31B magnesium alloy. Welding joint cracks along Cu/Mg interface, the surface is ductile-brittle hybrid fracture. The metallurgical connection of AZ31B magnesium alloys and Ti-6Al-4V titanium alloys were achieved when using Al foil as intermediate layer. The microstructure from Ti-6Al-4V side to AZ31B side at interface zone of diffusion brazing joint includes α-Ti solid solution, Ti3Al chemical compounds, (α-Mg+Mg2Al) eutectic structure and small amount of Mg17Al12 chemical compounds. The microhardness decreases of ladder shape. When the welding temperature was 540℃ and the holding time was 10min, the microhardness of the joint reached the maximum, about 306.87HV. As the welding temperature increases, the shear strength shows an increasing trend at first and then decreases. When the welding process is 540℃ keeping for 20min, the highest shearing strength of the joint can reach 71Mpa. Welding joint cracks along Ti/Al interface, and the fracture surface of joint showing dimples.