Contribution of ultrasonic surface rolling process to the fatigue properties of TB8 alloy with body-centered cubic structure

作     者：Dan Liu Daoxin Liu Mario Guagliano Xingchen Xu Kaifa Fan Sara Bagherifard Dan Liu;Daoxin Liu;Mario Guagliano;Xingchen Xu;Kaifa Fan;Sara Bagherifard

作者机构：College of Civil AviationNorthwestern Polytechnical UniversityXi'an 710072China Department of Mechanical EngineeringPolitecnico di MilanoMilan 20156Italy 

出 版 物：《Journal of Materials Science & Technology》 (材料科学技术（英文版）)

年 卷 期：2021年第61卷第2期

页      面：63-74页

核心收录：

学科分类：0806[工学-冶金工程] 0817[工学-化学工程与技术] 08[工学] 0805[工学-材料科学与工程（可授工学、理学学位）] 080502[工学-材料学] 0703[理学-化学] 0802[工学-机械工程] 0702[理学-物理学] 0801[工学-力学（可授工学、理学学位）] 

基　　金：the support of National Natural Science Foundation of China(51771155) National Science and Technology Major Project(2017-VII-0012-0107) Equipment Pre-research Field Fund(61409220202) 

主　　题：Ultrasonic surface rolling process Gradient structure layers Fatigue crack Rotating-bending fatigue TB8 alloys 

摘      要：The effect of ultrasonic surface rolling process(USRP) as a severe plastic deformation technology was investigated on the evolution of microstructure, residual stress and surface morphology of TB8 alloys with body-centered cubic structure. Stress-controlled rotating-bending fatigue tests indicated increased fatigue strength in USRP samples prepared using different number of passes compared to the base material, which was attributed to the presence of gradient structure surface layers. Five subsequent USRP passes resulted in the highest fatigue strength, due to the optimal surface properties including higher extent of grain refinement, larger compressive residual stresses, smoother surface morphology and increased micro-hardness. However, the effect of USRP technology on improving fatigue strength of TB8 alloy was not significant in comparison with that of other titanium alloys(for example, Ti6 Al4 V), which was attributed to the notable surface residual stresses relaxation revealed from measurements on postfatigued USRP samples. Electron backscatter diffraction analysis confirmed that fatigue crack initiation occurred in the larger grains on the surface with high Schmid factor. Small cracks were found to propagate into the core material in a mixed transgranular and intergranular mode. Further analysis indicated that grain growth existed in post-fatigued USRP-treated TB8 samples and that the average geometrically necessary dislocations value reduced after fatigue loading.