Ti2AlNb合金多层板结构超塑成形/扩散连接数值模拟及试验研究

Numerical Simulation and Technical Study on Superplastic Forming/Diffusion Bonding for Multi-sheet Structure of Ti2Al Nb Alloy

研究内容为Ti2Al Nb合金多层板结构的超塑成形/扩散连接(Superplastic forming/diffusion bonding,SPF/DB)工艺。采用恒应变速率法对Ti2Al Nb热轧板材进行单向拉伸试验,得到最佳超塑成形条件如下:变形温度=940℃,应变速率=0.000 5 s–1。利用MARC有限元软件对Ti2Al Nb合金多层板结构的超塑成形过程进行数值模拟,预测构件的壁厚分布情况和可能产生的缺陷。进行三层板和四层板结构的SPF/DB试验,采用优化的压力-时间曲线进行超塑成形的压力加载,扩散连接工艺参数如下:温度=940℃,压力p=10 MPa,时间t=180 min。结果表明,三层板结构在面板出现明显的沟槽现象,沟槽的深度为4.49mm,宽度为8.85 mm;四层板结构成形效果较好,表面平整,无褶皱、沟槽等缺陷;对扩散连接处的微观组织进行观察,显示扩散界面的连接质量良好。研究结果为Ti2A1Nb合金在航空航天复杂薄壁夹层结构件的制造方面提供了参考依据。

The superplastic forming/diffusion bonding（SPF/DB） processes of multi-sheet structure of Ti2 Al Nb alloy are studied. The uniaxial tensile tests of Ti2 Al Nb rolled sheets are carried out by using constant strain rate method and the optimal superplastic forming condition is obtained which the temperature is 940 ℃ and the strain rate is 0.000 5 s1. The SPF of multi-sheet structures of Ti2 Al Nb alloy is simulated by using the software MARC. The thickness distribution and the possible defects of structures are predicted. The SPF/DB experiments of three-sheet structure and four-sheet structure are done which the loading pressure of SPF processes are the optimized p-t curves and the parameters of diffusion bonding are as follow：=940 ℃, p=10 MPa, t=180 min. The results show that the panel of three-sheet structure appears grooves whose depth and width are 4.49 mm and 8.85 mm respectively. The forming quality of four-sheet structure is better and the surface is smooth without wrinkles, grooves and other defects. The microstructure of the joint interfaces is observed which shows an excellent bonding at the interfaces. The study provides a reference basis for the manufacture of complex thin-walled sandwich structures in aerospace of Ti2 Al Nb alloy.