退火和时效工艺对富镍Ti-Ni形状记忆合金显微组织和相变行为的影响  

Effects of annealing and aging processes on microstructure and phase transformation behavior of Ni-rich Ti-Ni shape memory alloys

作　　者：贺志荣[1] 王芳 HE Zhirong;WANG Fang(School of Materials Science and Engineering,Shaanxi University of Technology,Hanzhong 723001,China)

机构地区：[1]陕西理工大学材料科学与工程学院,陕西汉中723001

出　　处：《功能材料》2023年第6期6172-6178,共7页Journal of Functional Materials

基　　金：国家重点研发计划项目(2016YFE0111400)。

摘　　要：为了给富镍Ti-Ni形状记忆合金热处理工艺的优化提供依据,以Ti-50.8Ni合金丝为对象,用光学显微镜、透射电子显微镜和示差扫描量热仪研究了退火和时效工艺对富镍Ti-Ni合金显微组织、相变类型、相变温度和相变热滞的影响规律。Ti-50.8Ni合金丝经350~800℃+5~120 min退火处理后,随退火温度和时间增加,合金发生回复、再结晶和晶粒长大过程,再结晶温度在600℃左右,显微组织形态由纤维状向等轴状变化;冷却/加热相变类型由B2→R→B19′/B19′→R→B2型向B2→R→B19′/B19′→B2型向B2→B19′/B19′→B2型转变(B2-母相,CsCl型结构;R-R相,菱方结构;B19′-马氏体相,单斜结构);R相变温度θ_(R)先升后降,极大值35.2℃在400℃退火态合金中取得;马氏体(M)相变温度θ_(M)升高,M相变热滞Δθ_(M)降低,R相变热滞Δθ_(R)约为4℃。该合金经300~500℃+0.5~50 h时效处理后,随时效温度和时间增加,合金中Ti3Ni4析出物形貌由细小颗粒状→针状→粗片状变化;300℃和500℃时效态合金的相变类型分别为B2→R→B19′/B19′→R→B2和B2→R→B19′/B19′→B2,400℃时效态合金的相变类型由B2→R→B19′/B19′→R→B2型向B2→R→B19′/B19′→B2型转变;θ_(R300)、θ_(R400)、θ_(R500)、θ_(M300)和θ_(M500)升高;θ_(M400)先降后升,极小值-121.4℃在400℃+1 h时效态合金中取得;Δθ_(M300)和Δθ_(M400)先升后降,极大值70.5℃和129.4℃分别在300℃+5 h和400℃+1 h时效态合金中取得;Δθ_(M500)降低,Δθ_(R300)和Δθ_(R400)约为4℃。In order to provide a basis for optimizing the heat treatment process of Ni-rich Ti-Ni shape memory alloys,the effects of annealing and aging processes on the microstructure,phase transformation type,phase transformation temperature and temperature hysteresis of Ni-rich Ti-Ni alloys were investigated by optical microscope,TEM and differential scanning calorimetry with Ti-50.8Ni alloy wire as the object.After annealing at 350~800℃for 5~120 min in Ti-50.8Ni alloy wire,with the increase of annealing temperature and time,the reversion,recrystallization and grain growth of the alloy occur,the recrystallization temperature is about 600℃,and the microstructure morphology changes from fibrous to equiaxed.The transformation types of the alloy change from B2→R→B19′/B19′→R→B2 to B2→R→B19′/B19′→B2 to B2→B19′/B19′→B2(B2-parent phase,CsCl type;R-R phase,rhombohedral;B19′-martensite phase,monoclinic)upon cooling/heating.The R transformation temperatureθ_(R) increases first and then decreases,and the maximum value 35.2℃is obtained in the alloy annealed at 400℃.The martensite(M)transformation temperatureθ_(M) increases,the temperature hysteresis of M transformationΔθ_(M) decreases,and the temperature hysteresis of R transformationΔθ_(R) is about 4℃.After aging at 300-500℃for 0.5-50 h in Ti-50.8Ni alloy,with the increase of annealing temperature and time,the evolution role of the morphology of Ti 3Ni 4 precipitates is fine particle→needle-shape→plate-shape.The transformation types of the alloys aged at 300℃and 500℃are B2→R→B19′/B19′→R→B2 and B2→R→B19′/B19′→B2,respectively,and the ones of the alloys aged at 400℃change from B2→R→B19′/B19′→R→B2 to B2→R→B19′/B19′→B2.Theθ_(R300),θ_(R400),θ_(R500),θ_(M300)andθ_(M500) increase.Theθ_(M400) decreases first and then increases,and the minimum value-121.4℃is obtained in the alloy aged at 400℃for 1 h.TheΔθ_(M300)andΔθ_(M400) increase first and then decrease,and the maximum valu

关 键 词：TI-NI合金 Ti-50.8Ni合金 形状记忆合金 退火 时效 显微组织 相变 

分 类 号：TG113.25[金属学及工艺—物理冶金]