Constitutive behavior of nickel-titanium shape memory alloy （Ni-Ti SMA） under hot deformation was investigated by means of the compression tests and the linear fitting method. Based on the true stres-strain curves o...Constitutive behavior of nickel-titanium shape memory alloy （Ni-Ti SMA） under hot deformation was investigated by means of the compression tests and the linear fitting method. Based on the true stres-strain curves of Ni-Ti SMA under compression at the strain rates of 0.001-1 s land at the temperatures ranging from 600 to 1 000 ℃, the constitutive equation of Ni-Ti SMA with respect to the Zener-Hollomon parameter was established according to the high stress level and the low stress level at various temperatures so as to more accurately describe the deformation behavior of Ni-Ti SMA during hot working. Dynamic recovery and dynamic recrystallization of Ni-Ti SMA occur under hot compression, which lays the theoretical foundation for understanding the constitutive behavior of Ni-Ti SMA.展开更多
The reversible transformation between matrix and martensite in Ni-Ti shape memory alloys has been dynamically observed under TEM.The orientation relation between martensite and austenite as well as the structural chan...The reversible transformation between matrix and martensite in Ni-Ti shape memory alloys has been dynamically observed under TEM.The orientation relation between martensite and austenite as well as the structural change near the transition temperature has been also studied with the help of HREM SADP.The results show that the orientation relation between martensite and austenite is[11]_A//[10]_M,[110]_A//[001]_M,(110)_A//(001)_M and the angle between(110)_A and(010)_M is about 6.5°.The crystal defects of martensite are found to be twin and stacking fault,and the twin plane as(100).展开更多
The ribbons of the Ti45.3Ni54.7 shape memory alloy were prepared through the melt spinning technique. The study was focused on investigating the effect of the rapid solidification and grain size at characteristic star...The ribbons of the Ti45.3Ni54.7 shape memory alloy were prepared through the melt spinning technique. The study was focused on investigating the effect of the rapid solidification and grain size at characteristic start martensitic (Ms), final martensitic (Mf), start austenite (As) and final austenite (Af) transformation temperatures. Changes on martensitic transformation temperatures in Ti45Ni55 melt spun ribbons were observed as grain size is reduced. Results of optical microscopy and differential scanning calorimetry (DSC) were used to associate grain size with transformation temperatures.展开更多
利用形状记忆合金(SMA)的形状记忆效应,将它埋入复合材料中作为应变激励器,以改善复合材料结构内部的应力分布,控制孔边或损伤附近的应力集中,使结构具有强度自适应性。采用超奇异积分方程与边界元结合的方法,求解埋入 SMA 纤维的正交...利用形状记忆合金(SMA)的形状记忆效应,将它埋入复合材料中作为应变激励器,以改善复合材料结构内部的应力分布,控制孔边或损伤附近的应力集中,使结构具有强度自适应性。采用超奇异积分方程与边界元结合的方法,求解埋入 SMA 纤维的正交各向异性平面问题,分析SMA 动作前后孔边的应力,并给出数值计算结果与实验结果。展开更多
基金Project(51071056) supported by the National Natural Science Foundation of ChinaProjects(HEUCFR1132, HEUCF121712)supported by the Fundamental Research Funds for the Central Universities of China
文摘Constitutive behavior of nickel-titanium shape memory alloy （Ni-Ti SMA） under hot deformation was investigated by means of the compression tests and the linear fitting method. Based on the true stres-strain curves of Ni-Ti SMA under compression at the strain rates of 0.001-1 s land at the temperatures ranging from 600 to 1 000 ℃, the constitutive equation of Ni-Ti SMA with respect to the Zener-Hollomon parameter was established according to the high stress level and the low stress level at various temperatures so as to more accurately describe the deformation behavior of Ni-Ti SMA during hot working. Dynamic recovery and dynamic recrystallization of Ni-Ti SMA occur under hot compression, which lays the theoretical foundation for understanding the constitutive behavior of Ni-Ti SMA.
文摘The reversible transformation between matrix and martensite in Ni-Ti shape memory alloys has been dynamically observed under TEM.The orientation relation between martensite and austenite as well as the structural change near the transition temperature has been also studied with the help of HREM SADP.The results show that the orientation relation between martensite and austenite is[11]_A//[10]_M,[110]_A//[001]_M,(110)_A//(001)_M and the angle between(110)_A and(010)_M is about 6.5°.The crystal defects of martensite are found to be twin and stacking fault,and the twin plane as(100).
文摘The ribbons of the Ti45.3Ni54.7 shape memory alloy were prepared through the melt spinning technique. The study was focused on investigating the effect of the rapid solidification and grain size at characteristic start martensitic (Ms), final martensitic (Mf), start austenite (As) and final austenite (Af) transformation temperatures. Changes on martensitic transformation temperatures in Ti45Ni55 melt spun ribbons were observed as grain size is reduced. Results of optical microscopy and differential scanning calorimetry (DSC) were used to associate grain size with transformation temperatures.
文摘利用形状记忆合金(SMA)的形状记忆效应,将它埋入复合材料中作为应变激励器,以改善复合材料结构内部的应力分布,控制孔边或损伤附近的应力集中,使结构具有强度自适应性。采用超奇异积分方程与边界元结合的方法,求解埋入 SMA 纤维的正交各向异性平面问题,分析SMA 动作前后孔边的应力,并给出数值计算结果与实验结果。
