Deformation mechanism and in-situ TEM compression behavior of TB8βtitanium alloy with gradient structure  

作　　者：Dan Liu Daoxin Liu Junfeng Cui Xingchen Xu Kaifa Fan Amin Ma Yuting He Sara Bagherifard 

机构地区：[1]College of Civil Aviation,Northwestern Polytechnical University,Xi’an,710072,China [2]Key Laboratory for Precision and Non-Traditional Machining Technology of Ministry of Education,Dalian University of Technology,Dalian,116024,China [3]Department of Aeronautics and Astronautics,Air Force Engineering University,Xi’an,710038,China [4]Department of Mechanical Engineering,Politecnico di Milano,Milan,20156,Italy

出　　处：《Journal of Materials Science & Technology》2021年第25期105-115,共11页材料科学技术（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(No.51771155);the National Science and Technology Major Project(No.J2019-I-0016)。

摘　　要：Severe plastic deformation is known to induce grain refinement and gradient structure on metals’surfaces and improve their mechanical properties.However,the fundamental mechanisms behind the grain refinement and micromechanical properties of materials subjected to severe plastic deformation are not still well studied.Here,ultrasonic surface rolling process(USRP)was used to create a gradient microstructure,consisting of amorphous,equiaxed nano-grained,nano-laminated,ultrafine laminated and ultrafine grained structure on the surface of TB8βtitanium alloy.High energy and strain drove element co-segregation on sample surface leading to an amorphous structure during USRP processing.In situ transmission electron microscope compression tests were performed in the submicron sized pillar extracted from gradient structure and coarse grain,in order to reveal the micromechanics behavior of different grain morphologies.The ultrafine grained layer exhibited the lowest yield stress in comparison with single crystal and amorphous-nanocrystalline layers;the ultrafine grained layer and single crystal had an excellent strain hardening rate.The discrepancy among the grain sizes and activated dislocation sources led to the above mentioned different properties.Dislocation activities were observed in both compression test and microstructure evolution of USRP-treated TB8 alloy.An evolution of dislocation tangles and dislocation walls into low angle grain boundaries and subsequent high angle grain boundaries caused the grain refinement,where twinning could not be found and no phase transformation occurred.

关 键 词：TB8 alloy Ultrasonic surface rolling process Gradient microstructure Microstructure evolution In situ transmission electron microscope compression test 

分 类 号：TG146.23[一般工业技术—材料科学与工程]