TRANSFORMATION PSEUDO-ELASTICITY AND DEFORMATION-BEHAVIOR IN A TI-50.6AT-PERCENT NI-ALLOY
TRANSFORMATION PSEUDO-ELASTICITY AND DEFORMATION-BEHAVIOR IN A TI-50.6AT-PERCENT NI-ALLOY
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DOI：
10.1016/0036-9748(81)90346-x
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发表时间：
1981-01-01
期刊：
影响因子：
--
通讯作者：
SUZUKI, Y
中科院分区：
文献类型：
--
作者：
MIYAZAKI, S;OTSUKA, K;SUZUKI, Y
Ti-Ni合金以其形状记忆效应而闻名于世。事实上，它是目前商业上用于形状记忆效应的实际应用的唯一合金，例如联接器、连接器和医疗应用（1）。为了开发这样的应用，有必要研究与马氏体相变和/或马氏体状态相关的机械行为。迄今为止，沿着这条路线已经进行了沿着各种各样的调查，但是从基本观点来看，这些调查的数量和范围都不是很多，也不是那么深入。Rozner和Wasflewski（2），和Cross等人。(3)对较宽温度和应变范围内的应力-应变曲线（SS曲线）进行了相当系统的研究。发现Ti-Ni合金中的SS曲线由三个阶段组成，这与FCC和HCP单晶中的三个阶段非常相似。然而，他们没有研究卸载过程，也没有澄清这些阶段的性质。Wasflewski（5）和Honma（8）分别报道了Ti-51at%Ni和Ti-52at%Ni合金中相变伪弹性（4）的存在，但没有详细的数据，如温度依赖性等。本短文的目的是报道这种合金在某些dstafl中的相变伪弹性，并通过仔细观察加载和卸载时的应力-应变曲线以及通过测量卸载和随后加热时恢复的应变来阐明三个阶段的性质。已经进行了几项研究以澄清每个阶段的性质。虽然还没有很好地建立，但我们总结如下。Mohamed和Washburn（7）提供的证据表明，马氏体-马氏体界面在最初部分转变的材料的早期阶段（阶段I）发生移动。有些作者（7，8）提出，阶段H的变形是阶段I形成的马氏体的弹性变形。但Melton和Mercier（9）报告的证据与上述建议不一致。他们通过透射电子显微镜观察了变形到H阶段的试样的微观结构，并在某些部分发现了马氏体板条和位错的交叉阵列。然而，它们的观测仅限于II期的一个小区域，整个H期的变形模式也不清楚。在第III阶段，Mohamed和Washburn（7）对伸长8%的试样进行了电子显微镜观察，发现马氏体边界严重不规则。因此，他们建议，滑移发生在阶段HI。Michael（10）、Tadaki和Wayman（11）还对重冷轧（~ 30%）试样进行了电子显微镜观察，这大致相当于拉伸试验中的III阶段。他们都发现了高密度的位错和马氏体的分段。这些结果清楚地表明滑移发生在阶段HI，但缺乏关于应变恢复的拉伸试验的定性数据。同时，在Cu-Al-Ni单晶中，在特定取向上报告了明显非常相似的三个阶段的应力-应变曲线;在这种情况下，H和HI阶段的变形模式被明确地证明分别是由于马氏体的弹性变形和马氏体到马氏体的转变，通过在应力下用引伸计和中子衍射仔细测量应变（4）。将Ti-Ni合金中的三个阶段的性质与上述情况进行比较是有趣的。
The Ti-Ni alloy is so famous with the associated shape memory effect. In fact it is the only alloy which is used for the practical applications of the shape memory effect on a commercial basis at present, such as coupling, connectors and medical applications (1). In order to develop such applications, it is necessary to investigate mechanical behavior associated with the martensitic transformation and/or in the martensitic state. Various investigations have been made along this line so far, but the number and scope of these investigations are not very many nor so deep from a fundamental point of view. Rozner and Wasflewski (2), and Cross et al.(3) made rather systematic works on the stress-strain curves (SS curves) in wide temperature and strain ranges. They found that the SS curves in the Ti-Ni alloys consisted of three stages which are apparantly similar to three stages in FCC and HCP single crystals. However, they did not study the unloading process, and did not clarify the nature of these stages. The presence of the transformation pseudoelasticity (4) in Ti-51at% Ni and Ti-52at% Ni alloys has been reported by Wasflewski (5) and Honma (8) respectively, but no detailed data such as the temperature dependence etc. have been reported. The purpose of the present short note is to report the transformation pseudoelasticity in this alloy in some dstafl, and to clarify the nature of the three stages by carefully observing the stress-strain curves upon loading and unloading and by measuring the strains recovered upon unloading and subsequent heating.After the pioneering works by Rozner and Wasilewski, and Cross et al., several investigations have bean made to clarify the nature of each stage. Although it is not well established as yet, we summarize those in the following. Mohamed arid Washburn (7) have provided evidence that the martensite-martensite interface moves in the early stage (stage I) of an initially partially transformed material. Some authors (7, 8) have suggested that the deformation in stage H is an elastic deformation of the martensites formed in stage I. But Melton and Mercier (9) reported evidence inconsistent with the above suggestion. They observed microstructure in a specimen deformed into stage H by transmission electron microscopy and found an intersecting array of martensite laths in some part and dislocations in another part. However, their observation is limited to a small region of stage II, and the deformation modes throughout the stage H are not weU clarified. On stage HI, Mohamed and Washburn (7) made an electron microscopy observation of specimens elongated by 8% and found heavy irregularity of martensite boundaries. Thus they suggested that slip occurred at the stage HI. Michael (10) and Tadaki and Wayman (11) also made the electron microscopy observation of heavily cold-rolled (--30%) specimens, which roughly corresponded to stage HI in tensile tests. They both found high density of dislocations and the segmentation of martensites. These results are clear evidence to show that slip occurs in stage HI, but are lacking for the qualitative data by tensile tests as to the recovery of strains. Meanwhile, apparently quite similar three stage stress-strain curves are reported in Cu-A1-Ni single crystals in specific orientations; the deformation modes in stages H and HI in this case are proved unambiguously to be due to the elastic deformation of a martensite and martenalte-to-martensite transformation, respectively, by careful measurement of strains by extensometer and neutron diffraction under stress (4). It is interesting to compare the nature of the three stages in the Ti-Ni alloy with those in the above case.