Ni_(55)Ti_(45)形状记忆合金高温变形特性及机制  

High temperature deformation characteristic and mechanism of Ni_(55)Ti_(45) shape memory alloy

作　　者：舒小勇[1,2] 胡林丽[3] 鲁世强[1,2] 李贵发[1] 王克鲁[1] 

机构地区：[1]江西省金属材料微结构调控重点实验室(南昌航空大学),江西南昌330063 [2]南京航空航天大学材料科学与技术学院,江苏南京211106 [3]江西机电职业技术学院材料工程系,江西南昌330013

出　　处：《材料热处理学报》2017年第6期17-24,共8页Transactions of Materials and Heat Treatment

基　　金：国家自然科学基金(51164030);江西省教育厅科技项目(GJJ150703);江西省金属材料微结构调控重点实验室(南昌航空大学)开放基金(JW201523001)

摘　　要：采用Gleeble-3500热模拟试验机对锻态Ni_(55)Ti_(45)合金进行等温恒应变速率压缩实验,研究了该合金在变形温度为650~850℃、应变速率为0.01~1 s^(-1)范围内的高温变形特性,并分析其变形机制。结果表明,应力-应变曲线呈"应变软化"型,热变形激活能为317.304 k J/mol,根据双曲正弦函数建立了峰值流变应力本构方程。微观组织观察表明,在650℃、1 s^(-1)和700℃、1 s^(-1)时发生了局部塑性流动的失稳变形,主要由变形热效应导致。高温、低应变速率利于动态再结晶的发生,但动态再结晶晶粒尺寸更大。动态再结晶形核机制以晶界弓出机制为主,同时伴随有少量的PSN机制。The hot deformation characteristic and mechanism of as-forged Ni55 Ti45 shape memory alloy were investigated at deformation temperature range of 650 ℃ to 850 ℃ and strain rate range of 0.01 s^-1 to 1 s^-1 by a Gleeble-3500 thermal simulation machine. The results show that the flow stress of the alloy is greatly affected by strain rate and deformation temperature, and the flow stress decreases with the increasing of deformation temperature and the decreasing of strain rate. The deformation activation energy of the alloy is 317. 304 kJ/mol. A peak flow stress constitutive equation is established based on the hyperbolic sine equation. Microstrueture observation shows that the local plastic flow instability deformation occurs at 650 ℃ and 700 ℃ when strain rate is 1 s^-1 , which is mainly caused by deformation thermal effect. Higher temperature and lower strain rate are favorable for dynamic recrystallization, but the grain size of dynamic recrystallization is larger. The nucleation mechanism of dynamic recrystallization is dominated by the mechanism of grain boundary bulging, accompanied by a small amount of particle stimulated nucleation （PSN） mechanism.

关 键 词：Ni55Ti45形状记忆合金 高温变形特性 变形激活能 变形机制 

分 类 号：TG139[一般工业技术—材料科学与工程]