热处理对Ti-50.6Ni形状记忆合金相变和显微组织的影响  

Effect of heat treatment on phase transformation and microstructure of Ti-50.6Ni shape memory alloy

作　　者：贺志荣[1] 王芳 HE Zhi-rong;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：《材料热处理学报》2023年第5期95-103,共9页Transactions of Materials and Heat Treatment

基　　金：国家重点研发计划项目(2016YFE0111400)。

摘　　要：为了给形状记忆效应和超弹性优异的Ti-50.6Ni形状记忆合金实际应用时制订热处理工艺提供依据,采用示差扫描量热仪、光学显微镜和透射电镜等研究了退火和时效处理对Ti-50.6Ni形状记忆合金相变行为和显微组织的影响。结果表明:当退火温度由350℃升高到800℃时,Ti-50.6Ni合金冷却/加热相变类型由B2→R→B19′/B19′→R→B2(B2-母相,CsCl型结构;R-R相,菱方结构;B19′-马氏体,单斜结构)型向B2→R→B19′/B19′→B2型再向B2→B19′/B19′→B2型转变;R相变温度T_(R)先升后降,极大值36.44℃出现在400℃退火态合金中;马氏体相变温度T_(M)先升后降,极大值-19.98℃出现在600℃退火态合金中;M相变热滞ΔT_(M)降低;R相变热滞ΔT_(R)≈4℃;组织形态由纤维状向等轴状变化。随退火时间延长,T_(R)和T_(M)升高,ΔT_(M)降低,ΔT_(R)约为4℃。300℃和400℃时效态合金发生B2→R→B19′/B19′→R→B2型相变,500℃时效态合金发生B2→R→B19′/B19′→B2型相变,且T_(R)^(400)>T_(R)^(300)>T_(R)^(500),T_(M)^(500)>T_(M)^(400)>T_(M)^(300),ΔT_(M)^(300)>ΔT_(M)^(400)>ΔT_(M)^(500)≫ΔT_(R)^(300)≈ΔT_(R)^(400)≈4℃。随时效时间延长,T_(R)^(300)、T_(R)^(400)、T_(R)^(500)、T_(M)^(300)和T_(M)^(500)升高;T_(M)^(400)先降后升,极小值-87.30℃出现在400℃×1 h时效态合金中;ΔT_(M)^(300)升高;ΔT_(M)^(400)先升后降,极大值99.74℃出现在400℃×5 h时效态合金中;ΔT_(M)^(500)降低,ΔT_(R)^(300)和ΔT_(R)^(400)在3.81~5.53℃之间变化。随时效温度升高,该合金中Ti3Ni4析出物形貌由细小颗粒状→针状→粗片状变化。退火温度和时效温度对Ti-50.6Ni合金相变行为的影响远大于退火时间和时效时间。冷却方式不影响Ti-50.6Ni合金的相变行为。In order to provide the basis for formulating the heat treatment process of Ti-50.6Ni shape memory alloy with excellent shape memory effect and superelasticity in practical application,the effect of annealing and aging treatment on phase transformation behavior and microstructure of the Ti-50.6Ni shape memory alloy was studied by means of differential scanning calorimeter,optical microscope and transmission electron microscopy.The results show that with the increase of annealing temperature from 350℃to 800℃,the cooling/heating transformation type of the Ti-50.6Ni alloy changes from B2→R→B19′/B19′→R→B2(B2-parent phase,CsCl type;R-R phase,rhombohedral;B19′-martensite phase M,monoclinic)to B2→R→B19′/B19′→B2 type and then to B2→B19′/B19′→B2 type;the R transformation temperature T_(R)increases first and then decreases,and the maximum value of 36.44℃appears in the alloy annealed at 400℃;the martensitic transformation temperature T_(M)increases first and then decreases,and the maximum value of-19.98℃appears in the alloy annealed at 600℃;the temperature hysteresis of M transformationΔT_(M)decreases;the temperature hysteresis of R transformationΔT_(R)is about 4℃;the microstructure morphology changes from fibrous to equiaxed.With the increase of annealing time,the T_(R)and T_(M)increase,ΔT_(M)decreases,andΔT_(R)is about 4℃.The transformation type of the alloy aged at 300℃and 400℃is B2→R→B19′/B19′→R→B2;the transformation type of the alloy aged at 500℃is B2→R→B19′/B19′→B2,and T_(R)^(400)>T_(R)^(300)>T_(R)^(500),T_(M)^(500)>T_(M)^(400)>T_(M)^(300),ΔT_(M)^(300)>ΔT_(M)^(400)>ΔT_(M)^(500)≫ΔT_(R)^(300)≈ΔT_(R)^(400)≈4℃.With the increase of aging time,the T_(R)^(300),T_(R)^(400),T_(R)^(500),T_(M)^(300)and T_(M)^(500)increase,the T_(M)^(400)decreases first and then increases,and the minimum value of-87.30℃appears in the alloy aged at 400℃for 1 h;theΔT_(M)^(300)increases,theΔT_(M)^(400)increase first and then decrease,and the maximum va

关 键 词：Ti-50.6Ni合金 形状记忆合金 热处理 相变 显微组织 

分 类 号：TG139.6[一般工业技术—材料科学与工程]