以电子束为热源, 采用不同的束流功率对TC4钛合金进行刚性拘束热自压连接, 测试分析了连接接头界面焊合质量、组织和力学性能. 同时, 在实验基础上对刚性拘束热自压连接热应力应变过程进行有限元数值分析, 实验研究和数值模拟相结合分析了束流功率对连接接头界面焊合质量以及组织和性能的影响规律. 结果表明, 束流功率增加, 加热温度、高温区停留时间、高温区体积以及界面金属压缩塑性变形随之增加, 促进界面两侧原子扩散, 界面焊合质量提高. 束流功率显著影响连接接头组织, 小束流功率加热时能获得组织均匀的连接接头, 大束流功率加热时, 界面加热区产生针状a相, 且a/a相界取向差主要位于59.85°附近, 呈现出在同一b相晶粒内部产生的特点. 连接接头的力学性能受界面焊合率和加热区组织共同影响, 束流较小时, 界面未焊合缺陷多, 结合强度低; 束流较大时, 加热区发生显著组织转变, 晶粒粗大, 接头塑性差. 束流功率为330 W时, 接头组织均匀且界面焊合质量好, 获得综合力学性能优异的连接接头.

Rigid restraint thermal self-compressing bonding is a new solid-state bonding process. During the process, localized non-melted heating method is employed to heat the butted interface of the rigid restrained plates to be bonded. Under the localized heating, materials close to the butted interface are expanded. However, due to the existence of surrounding cool metals and rigid restraints, the expansion of the high temperature materials is restrained and thus, a compressive pressure is developed which compresses the high temperature metals near the bond interface and facilitates the atom diffusion between butt-weld specimens to produce a permanent solid-state joint. Utilizing the localized stress-strain field to accomplish atomic bonding, this process can avoid the use of external forces on which diffusion bonding and other solid-state bonding methods rely. Previous study has proven the feasibility of this process to join titanium alloys. In present work, the effect of beam power on bond interface, microstructure and mechanical properties of the TC4 joints bonded at different beam powers were analyzed through the OM observation, EBSD analysis, mechanical property test and fracture morphology analysis. Meanwhile, in order to reveal the mechanism about the effect of beam power on bond interface, the experiment study on microstructure and mechanical property and finite element analysis on present bonding were conducted to investigate the effect of beam power on the thermal stress-strain process during bonding. The results show that with the increase of beam power, the heating temperature, dwell time over high temperature, volume of materials with high temperature and the compressive plastic strain increase which promote the atom diffusion and thus bond quality of the interface is improved. At low beam power, the microstructure of the joints is homogeneous, while coarse grain with acicular a phase forms in the joint when the beam power is high. Mechanical properties of the joint are dependent on bond rate and microstructure. When the beam power is lower or higher, the compressive mechanical properties of the joints are poor because of the poor bonding quality of the interface or the coarse microstructure developed in the joint. Good comprehensive mechanical properties are obtained at the beam power of 330 W.