CT1400低温钛合金的显微组织与力学性能

Microstructure and mechanical properties of CT1400 cryogenic titanium alloy

针对大推力运载火箭对高性能低温钛合金材料的需求,设计了一种新型1500 MPa级Ti-Al-V-Zr-Mo-Nb低温钛合金(CT1400),制备棒材及粉末冶金材料,并对其显微组织、拉伸性能和低温拉伸变形机理进行观察与分析。结果表明:CT1400低温钛合金主要由α相和少量β相组成,是一种典型的近α型低温钛合金。其棒材形成明显的等轴细晶组织,粉末冶金材料则是以片层组织为主的“网状”结构组织特征。两种方法制备的CT1400钛合金均具有优异的室温及低温拉伸性能,位错强化与晶界强化共同作用可稳定实现低温强度1500 MPa级别。此外,合金20 K低温条件下的孪生变形可通过协调晶体学取向特征、促进应变硬化等措施进一步提高CT1400钛合金的低温塑性,使其具备优异的低温强塑性。

In urgent demand for high-performance cryogenic titanium alloy for the heavy-lift launch vehicle,a novel 1500 MPa Ti-Al-V-Zr-Mo-Nb cryogenic titanium alloy(CT1400)was designed.Alloy bars and powder metallurgy materials of CT1400 were fabricated,and the microstructure,tensile properties,and cryogenic tensile deformation mechanism were also observed and analyzed.The results indicate that the CT1400 cryogenic titanium alloy mainly consists ofαphase and a small quantity ofβphase,which shows a typical near-αtype cryogenic titanium alloy.CT1400 alloy bars display the apparent equiaxed fine-grain microstructure characteristic,and the powder metallurgy materials show the dominating lamellar microstructure combing with the“network”structure characteristic.CT1400 titanium alloys display excellent room and cryogenic tensile properties,which can stably reach cryogenic stress of 1500 MPa resulting from dislocation strengthening and grain boundary strengthening mechanisms.Furthermore,the twinning deformation at the cryogenic temperature of 20 K could additionally improve the cryogenic plastic deformation capacity of CT1400 titanium alloy by coordinating crystal orientation,promoting strain hardening,making it represent excellent coupling of strength and ductility at cryogenic temperatures.