PRICM-5

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Authors: Xiang Ming He, De Sheng Yan, Zhi Min Jiang, Li Jian Rong
Abstract: A ternary alloying element Niobium addition to the Ni-Ti shape memory alloy could optimize transformation temperatures, mechanical properties. In this paper, with the help of ambient tensile test and scan electron microscope observation, the influences of Nb-content on the mechanical properties of (Ni47Ti44)100-xNbx alloys were investigated in detail. The results indicated that both the fracture strength (sb) and the elongation (d) decreased gradually with the increasing of the Nb content. The fracture surfaces showed the fracture character of the alloys was clearly gliding fracture, which is typically transgranular fracture mode.
1945
Authors: Toshio Sakuma, Yuji Mihara, Yasuo Ochi, M. Ozawa, K. Okita, N. Okabe
Abstract: Ti-Ni-Nb shape memory alloy has a wide transformation hysteresis, and has been used as coupling devices and so on. However systematic researches of the influence of the amount of Nb addition on transformation temperatures are few. The purpose of this work is to clarify the influences of pre-strain and Nb content on transformation temperatures in Ti-Ni-Nb shape memory alloys. The specimens were Ti-Ni-Nb alloys (Ni/Ti=1.0, Nb=0-15at%), annealed at 1223 K for 0.3 ks. The variation of transformation temperatures with pre-strain and Nb content were investigated experimentally. The variation of As, Ms and transformation temperature hysteresis with pre-strain and Nb content will be discussed in relation to the elastic strain energy and the volume fraction of slip-deformed martensite.
1949
Authors: Keisuke Okita, Nagatoshi Okabe, Toshio Sakuma, Hiromasa Semba, Yuji Mihara
Abstract: Thermo-mechanical characteristic of shape memory alloy depends on cold working and heat treatment, because these processes can control the amount of defects including dislocation and precipitation [1]. In this study, the influence of cold working on the deformation behavior and the transformation characteristics was investigated on the Ti-Ni-Nb shape memory alloy (SMA). Both the tensile test and the shape recovery test were performed for the wire specimens of 1mm in the diameter with some different rates of cold working. The shape recovery tests were performed for the wire specimens of different cold working rates until the various levels of maximum applied strain, and the reverse-transformation characteristics on the process of heating after unloading were studied. It is clarified that the higher cold-working rate improves the shape memory properties of the alloy.
1953
Authors: Lei Wang, De Sheng Yan, Zhi Min Jiang, Li Jian Rong
Abstract: In order to improve the performance of pipe couplings, a technique has been developed to electroplate copper on the inner surface of Ni-Ti-Nb pipe-joints after pre-deformation. Gas leak tightness and tensile tests were conducted to evaluate the performance of the couplings both with and without copper coating. It was found that electroplating a thin copper layer on the inner surface of the pipe-joint effectively solved the problem of leakage and greatly enhanced the pull-out force of the couplings. Furthermore, the pipe-joints without ribs can be demounted easily after being cooled to the liquid nitrogen temperature and benefit the maintenance of the pipeline.
1957
Authors: H. Kyogoku, T. Kadomura, S. Komatsu, Fusahito Yoshida, Toshio Sakuma
Abstract: Ti-Ni-Cu shape memory alloy by elemental powders was fabricated by using a pulse-current pressure sintering method, and it was subjected to solid-solution heat treatment after sintering to homogenize the microstructure of the alloy. The influence of the thermo-mechanical cyclic deformation on the shape memory and thermo-mechanical characteristics of Ti-Ni-Cu alloy was investigated. The thermo-mechanical cyclic deformation improved the deformation behavior of the sintered alloy and made the thermo-mechanical behavior of the alloy stable caused by the introduction of dislocations. As a result, the recovery stress of the alloy after the cyclic deformation fairly increased. The transformation temperatures of the alloy after the cyclic deformation became lower than those of the alloy before the cyclic deformation. Therefore, the superelastic-like behavior of the alloy after the cyclic deformation appeared in an isothermal tensile test at lower holding temperature.
1961
Authors: Yeon Wook Kim, Tae Hyun Nam
Abstract: Transformation behaviors and shape memory characteristics of Ti–Ni45-Cu5 alloy ribbons prepared by melt spinning were investigated by means of DSC, XRD and OM. In these experiments particular attention has been paid to change the ejection temperature of the melt from 1400°C to 1600 °C. As the results, the thickness of ribbons could be controlled. An increase of the superheat of the melt leads to a reduced ribbon thickness and a refinement of grains. The microstructural refinement and the increased internal strains achieved by controlling the melt-spinning temperature decreased Ms significantly. It was also found that two-step transformation (B2-B19-B19’) occurred in the ribbons fabricated at higher melt-spinning temperatures than 1450°C.
1965
Authors: Fu Shun Liu, Yanping Qian, Hui Bin Xu
Abstract: Static and dynamic mechanical behavior of Ti50Ni47Fe3 shape memory alloy was investigated by mechanical tensile test and instrumention impact test under a wide temperature range from -196°C to 20°C. The instrumention impact test was carried out under different temperatures at which the alloys are with martensite, austenite and R phase, respectively. It is found that the alloy with austenite performed the best ductility, the samples with martensite and R phase exhibit superior and inferior ductility, respectively.
1969
Authors: Ailian Liu, Xianglong Meng, Wei Cai, Lian Cheng Zhao
Abstract: The effect of cerium addition on the martensitic transformation behavior and microstructure of Ti50-x/2Ni50-x/2Cex (x=0, 0.5, 2, 5 and 10at.%) alloys have been studied by differential scanning calorimetry (DSC) and energy dispersive spectroscopy (EDS). The results show that the addition of cerium affects the martensitic transformation temperature obviously. With the increase of Ce content, the phase transformation temperatures first increase rapidly and then decrease slightly, which may be attributed to the change of the Ni/Ti ratio in matrix. Moreover, the dispersed Ce-riched second particles with various morphologies are observed in TiNiCe alloys.
1973
Authors: Mi Seon Choi, Takashi Fukuda, Tomoyuki Kakeshita
Abstract: Martensitic transformation behavior of a series of Ti-(50-x)Ni-xCo at% alloys (x = 4, 8, 12, 16, 20) has been examined by electrical resistivity, magnetic susceptibility and specific heat measurements, in order to know the phase stability of the B2-type structure. The 4Co and 8Co alloys exhibit a typical first order B2-R-B19' transformation. The 12Co alloy probably transforms to the R-phase, but its microstructure is composed of small domains with about 10 nm in diameter, being quite different from the microstructure of a typical R-phase formed by nucleation and growth. The 16Co and the 20Co alloys do not show any martensitic transformation but anomalies of the electrical resistivity and magnetic susceptibility being similar to those of the 12Co alloy appear in these alloys. The diffuse scattering of 1/3<110> is also observed in the 16Co alloy. The Debye temperature decreases and electronic specific heat coefficient increases with increasing Co content.
1977
Authors: Tomonari Inamura, Hideki Hosoda, Kenji Wakashima, Shuichi Miyazaki
Abstract: Anisotropy in elastic properties of Ti-24mol%Nb-3mol%Al (TiNbAl), a new biomedical shape memory alloy developed by our group, was characterized in a temperature range from 133K to 413K. A well developed <110>{112}-type recrystallization texture is formed by an annealing at 1273K for 1.8ks after a severe cold-rolling. Young’s modulus of the -phase exhibited a strong anisotropy depending on the loading direction. Young’s modulus along of -phase of TiNbAl around room temperature was estimated to be , with assuming that the texture is perfectly developed.
1983

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