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中文摘要: 对固溶处理后的Ti-2.5Cu合金分别施加0.05、0.1、0.15、0.2的拉伸预应变,随后进行一次时效(400℃×24 h/AC)和二次时效处理(475℃×8 h/AC),研究了预应变时效处理对Ti-2.5Cu合金拉伸性能和低周疲劳性能的影响。结果表明:二次时效后析出的Ti_2Cu粒子尺寸较一次时效有了明显的长大;一次时效处理的合金强度随预应变量的增加而升高,而二次时效处理的合金强度随预应变量的增加先增加,当预应变量超过0.15后,开始下降;2种时效工艺处理的合金延伸率均保持在较高的水平。在考虑应变回复的基础上,建立了Ti-2.5Cu合金预应变时效的强度预测模型,其理论预测值与实验结果相吻合;一次时效和二次时效后的疲劳寿命相当,都表现为循环软化,疲劳裂纹以穿晶方式扩展。通过预应变时效处理可以提高Ti-2.5Cu合金的综合力学性能。
Abstract:After solution treatment,prestrains with 0.05, 01, 0.15 and 0.2 were applied to Ti-2.5 Cu alloy samples followed by first(400 ℃×24 h/AC) and second(475 ℃×8 h/AC) aging treatments and the corresponding tensile and low cycle fatigue(LCF) behaviors were investigated. The results show that the larger Ti_2Cu particles are observed after the second aging compared to the first aging. The yield strength increases with the prestrains for the first aging. Whereas the strength firstly increases with the prestrain while reduction in strength is observed when prestrain exceeds 0.15 for the second aging. Meanwhile, elongation of pretrained and aged Ti-2.5 Cu samples keeps in a same level with those unstrained ones. Considering strain recovery, the strength model of Ti-2.5 Cu alloy with prestrain and aging is established, which is in well agreement with experimental results. LCF results show that the similar LCF life and cycle softening are observed for both aging treatments. The fractography analyses suggest that transgranular fracture with well developed fatigue striations is the predominant failure mode. It can be concluded that the process of prestrain followed by aging is a useful method to obtain good mechanical properties of Ti-2.5 Cu alloy.
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