TC11钛合金室温高周疲劳断口及微观组织
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摘要
以片层组织TC11钛合金为研究对象,借助光学显微镜(OM)、扫描电镜(SEM)和透射电镜(TEM)对室温高周疲劳断口及断口附近的微观组织形貌进行了观察分析。研究结果表明:不同载荷下TC11钛合金疲劳断口均由疲劳源区、裂纹扩展区和瞬断区3部分组成,且裂纹扩展区存在着大量与疲劳裂纹扩展方向相垂直的二次裂纹。随着载荷的增大,二次裂纹数量逐渐增多的同时,其宽度明显增加,疲劳辉纹的宽度也随之增大,从0. 6μm(475 MPa)增加到1. 0μm(525 MPa)。在交变载荷的作用下,钛合金内部萌生出大量的位错亚结构,且位错多堆积在α/β相界处,造成应力集中,导致界面开裂形成裂纹源,从而降低疲劳寿命。
The fatigue fracture and microstructure near the fatigue fracture of TC11 titanium alloy after high cycle fatigue were analyzed by means of optical microscope( OM),scanning electron microscopy( SEM) and transmission electron microscopy( TEM). The results show that the fatigue fracture under different loads is composed of fatigue source area,crack propagation area and transient breaking area. Meanwhile,there are large amounts of secondary cracks perpendicular to propagation directions of the fatigue crack. With the load increasing,the number of secondary cracks and the width of the cracks increase,as well as the width of fatigue striations. When the load is from 475 MPa to 525 MPa,the width of fatigue striations increases from 0. 6 μm to 1 μm. Under alternating load,a large number of dislocation substructures are emerged in titanium alloy,and high density dislocation pile-up lies in the interface of α and β,leading to the stress concentration. Finally,the crack source is formed and the fatigue life is reduced.
The fatigue fracture and microstructure near the fatigue fracture of TC11 titanium alloy after high cycle fatigue were analyzed by means of optical microscope( OM),scanning electron microscopy( SEM) and transmission electron microscopy( TEM). The results show that the fatigue fracture under different loads is composed of fatigue source area,crack propagation area and transient breaking area. Meanwhile,there are large amounts of secondary cracks perpendicular to propagation directions of the fatigue crack. With the load increasing,the number of secondary cracks and the width of the cracks increase,as well as the width of fatigue striations. When the load is from 475 MPa to 525 MPa,the width of fatigue striations increases from 0. 6 μm to 1 μm. Under alternating load,a large number of dislocation substructures are emerged in titanium alloy,and high density dislocation pile-up lies in the interface of α and β,leading to the stress concentration. Finally,the crack source is formed and the fatigue life is reduced.
引文
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[2]金和喜,魏克湘,李建明,等.航空用钛合金研究进展[J].中国有色金属学报,2015,25(2):280-292.
[3] SANTHOSH R,GEETHA M,RAO M N. Recent developments in heat treatment of betat titanium alloys for aerospace applications[J]. Transactions of the Indian institute of metals,2017,70(7):1681-1688.
[4] LIU H B,HUANG W N,WEI C. Investigation on high cycle fatigue-low cycle fatigue life of alloy material[J]. Journal of aerospace power,2014,29(1):74-80.
[5] LUO S H,NIE X F,ZHOU L C,et al. High cycle fatigue performance in laser shock peened TC4 titanium alloys subjected to foreign object damage[J]. Journal of materials engineering&performance,2018,27(3):1466-1474.
[6] ZHONG L,ZHEN Y,LIANG Y,et al. Property of high cycle fatigue of TC11 under residual stress and different stress ratios[J]. Rare metal materials&engineering,2015,44(5):1224-1228.
[7] YU H J,FAN R Y,HUANG J,et al. Microstructure and mechanical properties of high-strength TC11 titanium alloy joints welded by laser beam[J]. Chinese journal of nonferrous metals,2015,25(1):1-8.
[8] SONG Z M,LEI L M,ZHANG B,et al. Microstructure dependent fatigue cracking resistance of Ti-6. 5Al-3. 5Mo-1. 5Zr-0. 3Si alloy[J]. Journal of materials science&technology,2012,28(7):614-621.
[9] ZHANG B,SONG Z M,LEI L M,et al. Geometrical scale-sensitive fatigue properties of Ti-6. 5Al-3. 5Mo-1. 5Zr-0. 3Si alloys withα/βlamellar microstructures[J]. Journal of materials science&technology,2014,30(12):1284-1288.
[10] NIE X F,HE W F,ZANG S L,et al. Effect study and application to improve high cycle fatigue resistance of TC11 titanium alloy by laser shock peening with multiple impacts[J]. Surface&coatings technology,2014,253(9):68-75.
[11]赵振华,陈伟.高低周复合载荷对TC11钛合金疲劳性能的影响[J].航空动力学报,2011,26(11):2468-2474.
[12]钟丽琼,严振,梁益龙,等.残余应力场和不同应力比下TC11钛合金的高周疲劳性能[J].稀有金属材料与工程,2015,44(5):1224-1228.
[13]王芳,王忠堂. TC11钛合金热压缩变形时微观组织演变规律研究[J].热加工工艺,2015,44(11):65-67.
[14]岳赟. Ti Zr基合金组织调控及疲劳行为研究[D].秦皇岛:燕山大学,2017.
[15]林翠,杜楠.钛合金选用与设计[M].北京:化学工业出版社,2014:100-152.
[16]严振.残余应力场及表面完整性对TC11钛合金和高温合金疲劳性能的影响[D].贵阳:贵州大学,2015.
[17]王宏权,李进元,郭征,等.热变形及热处理工艺对TC11钛合金棒材显微组织和力学性能的影响[J].热加工工艺,2017(13):160-162.
[18] YUE Y,DAI L Y,ZHONG H,et al. Effect of microstructure on high cycle fatigue behavior of Ti-20Zr-6. 5Al-4V alloy[J].Journal of alloys&compounds,2017,696:663-669.
[19]霍东兴,梁精龙,李慧,等.钛合金研究及应用进展[J].铸造技术,2016,37(10):2065-2066.
[20]宋鸿武,张士宏,程明,等.钛合金片层组织两相区变形时的流动软化机理分析[J].金属学报,2011,47(4):462-468.