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对于经过冷变形的固溶态Ti-10Mo-8V-1Fe-3.5Al(TB3)合金,透射电子显微镜(TEM)观察结果表明:其内部冷变形产生的高密度位错在常规时效后依然大量存在,这将导致合金材料力学性能的劣化。针对此问题,本实验研究了一种二次时效工艺,在常规时效基础上增加了短时间高温时效阶段。TEM观察结果表明,二次时效工艺处理后,合金内部位错密度大幅降低,与此同时时效析出的α片出现了变体选择效应。对经过冷变形及二次时效工艺处理后的TB3合金试样(SA试样)和未变形的常规峰值时效状态试样(FA试样)进行低周轴向拉压疲劳测试结果表明:在总应变幅低于0.01时,SA试样疲劳寿命稍高;总应变幅高于0.01时,FA试样疲劳寿命稍高。另外,对低周疲劳测试后的试样TEM观察结果表明:(1)位错滑移是该合金低周疲劳过程中的主要变形方式;(2)低周疲劳产生的位错条带结构在FA试样中较宽且不连续,而在SA试样中细小均匀。
Transmission electron microscopy (TEM) observations of cold-deformed solid solution Ti-10Mo-8V-1Fe-3.5Al (TB3) alloy show that high density dislocations due to internal cold deformation remain abundant after conventional aging , Which will lead to the deterioration of mechanical properties of alloy materials. In response to this problem, this study studied a secondary aging process, based on the conventional aging added a short period of high temperature aging stage. The results of TEM observation show that the dislocation density in the alloy decreases greatly after the secondary aging treatment, while the α-sheet precipitated during aging shows the effect of variant selection. The test results of low-frequency axial tension and compression tests on TB3 alloy specimens (SA specimens) and non-deformed conventional peak aged specimens (FA specimens) after cold deformation and secondary aging treatment showed that in the total When the strain amplitude is less than 0.01, the fatigue life of SA specimen is slightly higher; when the total strain amplitude is higher than 0.01, the fatigue life of FA specimen is slightly higher. In addition, the TEM observation results of the samples after low-cycle fatigue test show that: (1) dislocation slip is the main deformation mode during the low-cycle fatigue of the alloy; (2) dislocation band structure caused by low cycle fatigue The FA sample is wide and discontinuous, while it is small and uniform in the SA sample.