热暴露对Ti3Al/TC11双合金连接界面组织和拉伸性能的影响

对550℃热暴露50h的Ti3Al/TC11双合金拉伸试样用OM和SEM观察连接界面在近等温锻造、热处理和热暴露后的组织与断口形貌。结果表明:梯度热处理条件下,随着变形量的增加,试样热暴露后室温抗拉强度升高;连接界面上锻造形成的细针状α交织组织在热暴露期间发生分解、粗化,同时焊缝中析出更多细小的球状α/α2相。采用梯度热处理的双合金试样热暴露后强度稍高于经双重热处理的试样,双重热处理试样中Ti3Al基合金热影响区的α2相在热暴露期间发生长大。由于氧化造成表面微裂纹,使得试样直接热暴露性能低于毛坯热暴露性能。从拉伸断裂位置可以看出,断裂主要发生在Ti3Al基合金侧。

Effect of Thermal Exposure on Microstructure and Mechanical Properties in Welding Seam of Ti3Al/TC11 Dual Alloy

The microstructures and fracture morphologies at the weld interfaces of near isothermally forged and heat treated Ti3Al/TC11 dual alloy after thermal exposure at 550 °C for 50 h were investigated through tensile experiment and using OM and SEM.The results indicate that under gradient heat treatment the tensile strength of dual alloy after thermal exposure increases as the increase of the deformation degree;meanwhile,the interlaced structures of the acicular α phase in weld interface decompose and coarsen,and more fined sphericity α/α2 phases precipitate in weld.The strength of the dual alloy processed by gradient heat treatment is slightly higher than that by double heat treatment after thermal exposure.α2 phase in Ti3Al HAZ of specimen processed by double heat treatment grows up during thermal exposure.Mechanical properties of the specimen without oxidation surface are superior to that with oxidation surface due to the surface microcrack caused by oxidation.It can be found that fracture predominantly occurs in Ti3Al base alloy from the facture position of specimens.