摘要
TNW700钛合金是我国自主研发的近α型、可在700℃短时使用的高温钛合金。针对TNW700合金板材在温度为890~950℃、恒应变速率为0.0100~0.0005 s^(-1)下的单向超塑拉伸变形行为进行了研究,利用Zener-Hollomn参数和Arrhenius方程建立了TNW700钛合金的峰值应力本构方程。结果表明:TNW700钛合金的超塑性变形行为与普通钛合金不同,其加工硬化阶段较长,且温度越高、应变速率越低,动态硬化的效果更加明显,远高于再结晶软化程度,晶粒尺寸的增加是导致加工硬化的主要原因。在950℃,0.0005 s^(-1)条件下获得的最大延伸率为933%。所建立的峰值应力方程为σ_p=17.414[1.047(lnε+540210/RT)-46.587],其变形激活能Q=540.21 k J·mol^(-1)。在较低温度条件下变形,在断口附近由于应变速率高和变形温度低的双重作用在晶界三角区产生应力集中使晶界滑移变得困难而导致有孔洞产生。随着变形温度的升高,β相含量和尺寸逐渐增加,高温、高应变速率条件下有次生α相析出,采用电子探针分析(EPMA)发现β晶粒微区成分的变化是次生α相产生的主要原因。
TNW700 titanium alloy as a near-α high-temperature titanium alloy which could be used for a short term service at 700 ℃. The superplasticity of TNW700 titanium alloy sheet under the conditions of 890 - 950 ℃ and 0.0100 - 0.0005 s - 1 was studied. The results showed the superplastic deformation behavior of TNW700 alloy was significantly different from the common titanium alloy, whose work hardening period represented much longer than dynamicrecrystallization （DRX） period when at the higher deformation tem- perature and the lower strain rate. The main reason was the coarsening of grain size. The maximum elongation obtained at 950 ℃ and 0. 0005 s-1 was 933%. A constitutive equation based on the Zener-Hollomn parameter and Arrhenius equation was defined for TNW700 alloy, and the deformation energy Q = 540.21 kJ.mol^-1. Due to the double function of low deformation temperature and strain rate at triple junctions which caused local stress concentration, the boundary sliding became much more difficult and thus some cavities would be caused near the fracture. The volume fraction and grain size of β increased with the increase of deformation temperature, the second α phase would be generated under higher temperature and strain rate, and the change of chemical composition in β grains was the main reason of the generation of second α phase by electron probe micro analysis （EPMA）.
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2016年第1期1-7,共7页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(51405458)
航空研究项目(61901110301)资助
关键词
TNW700钛合金
超塑性
本构方程
显微组织
TNW700 titanium alloy
superplasticity
constitutive equation
microstructure
