Microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with different prestrain levels  

作　　者：Y.H.Zhang H.Li Z.W.Yang X.Liu Q.F.Gu 

机构地区：[1]State Key Laboratory of Solidification Processing,School of Materials Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China [2]Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment,Northwestern Polytechnical University,Xi’an 710072,China

出　　处：《Journal of Materials Science & Technology》2024年第4期80-93,共14页材料科学技术（英文版）

基　　金：support from the National Natural Science Foundation of China(No.51775441);the National Science Fund for Excellent Young Scholars(No.51522509).

摘　　要：Ni_(47)Ti_(44)Nb_(9)shape memory alloy(SMA)is a promising material in the aerospace field due to its wide transformation hysteresis.The application of shape memory effect depends on multistep thermomechan-ical loading,viz.,low-temperature deformation and subsequent heating to recovery.Low-temperature deformation prestrain plays a pivotal role in shape memory properties tailoring of SMA components.However,microstructure evolution and deformation mechanisms of Ni_(47)Ti_(44)Nb_(9)SMA subjected to vari-ous prestrain levels are still unclear.To this end,microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with prestrain levels of 8%-16%at-28℃(M_(s)+30℃)were investigated.The results demonstrate that the stress-strain curve of the specimen exhibits four distinct stages at a maximal prestrain of 16%.Whereas stageⅡand stageⅢend at prestrains of∼8%and∼12%,respectively.In stageⅡ,the stress-induced martensitic transformation is accompanied by the dislocation slip of the NiTi matrix andβ-Nb inclusions.In stageⅢ,in addition to the higher density of dislocations and further growth of stress-induced martensite variants(SIMVs),(001)compound twins are introduced as a result of the(001)deformation twinning in stress-induced martensite.More{20-1}martensite twins are gradually introduced in stageⅣ.Correspondingly,after subsequent unloading and heating,a higher density of{114}austenite twins form in the specimen with a larger prestrain of 16%.With increasing prestrain from 8%to 16%,the recoverable strainε_(re)^(T)upon heating increases first and then decreases.Theε_(re)^(T)obtains a maximum of 7.03%at 10%prestrain and de-creases to 6.17%at 16%prestrain.The increase ofε_(re)^(T)can be attributed to the formation of new SIMVs,the further growth of existing SIMVs,and the recoverable(001)compound twins.While the decrease ofε_(re)^(T)is mainly associated with the irrecoverable strain by{20−1}martensite twins.The effect ofβ-Nb inclusions o

关 键 词：Ni_(47)Ti_(44)Nb_(9)shape memory alloy Wide transformation hysteresis Thermomechanical loading Microstructure evolution Shape memory behaviors Stress-induced martensitic transformation Deformation twinning 

分 类 号：TB333[一般工业技术—材料科学与工程] TG139.6[金属学及工艺—合金]