Inverse gradient nanostructure through gradient cold rolling demonstrated with superelasticity improvement in Ti-50.3Ni shape memory alloy  

作　　者：Jian Zhang Ke Liu Tong Chen Chen Xu Chen Chen Dingshun Yan Ann-Christin Dippel Jun Sun Xiangdong Ding 

机构地区：[1]Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology,Jiangnan University,Wuxi 214122,China [2]State Key Laboratory for Mechanical Behavior of Materials,Xi’an Jiaotong University,Xi’an 710049,China [3]School of Materials Science and Engineering,Central South University,Changsha 410083,China [4]Deutsches Elektronen-Synchrotron DESY,Notkestrasse 85,Hamburg 22607,Germany

出　　处：《Journal of Materials Science & Technology》2024年第18期233-244,共12页材料科学技术（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.52171007,52101166,51931004);the 111 Projects 2.0(Grant No.BP0618008).

摘　　要：Gradient nanostructured(GNS)metallic materials are commonly achieved by gradient severe plastic de-formation with a gradient of nano-to micro-sized structural units from the surface/boundaries to the center.Certainly,such GNS can be inversely positioned,which however has not yet been reported.The present work reports a facile method in deformation gradient control to attain inverse gradient nanostructured(iGNS),i.e.,tailoring the cross-section shape,successfully demonstrated in Ti-50.3Ni shape memory alloy(SMA)wire through cold rolling.The microstructure of the rolled wire is characterized by a macroscopic inverse gradient from boundaries to the center—the average sizes of grain and martensite domain evolve from micrometer to nanometer scale.The iGNS leads to a gradient martensitic transforma-tion upon stress,which has been proved to be effectively reversible via in-situ bending scanning electron microscopy(SEM)observations.The iGNS Ti-50.3Ni SMA exhibits quasi-linear superelasticity(SE)in a wide temperature range from 173 to 423 K.Compared to uniform cold rolling,the gradient cold rolling with less overall plasticity further improves SE strain(up to 4.8%)and SE efficiency.In-situ tensiling synchrotron X-ray diffraction(SXRD)analysis reveals the underlying mechanisms of the unique SE in the iGNS SMAs.It provides a new design strategy to realize excellent SE in SMAs and sheds light on the advanced GNS metallic materials.

关 键 词：Inverse gradient nanostructured metallics Gradient cold rolling Shape memory alloys Gradient martensitic transformation SUPERELASTICITY 

分 类 号：TG139[一般工业技术—材料科学与工程] TB383.1[金属学及工艺—合金]