The Study of the Mechanism of the All-Round Shape Memory Effect in TiNi Alloy

富镍钛合金（Ti-51 - 52at%Ni）显示了受约束老化影响的全圆形状记忆效应。这个研究项目的目标是澄清这种全圆形状记忆效应的机制。Ti-51和52 at %Ni specimens对光学显微镜和电镜显微镜的各种受约束老化条件的影响进行了调查。结果如下所示：1。该合金在300-600 ° C之间产生的TTT图表。Precipitates were<Ti_3><Ni_4>（precisely<Ti_11><Ni_14>）、<Ti_2><Ni_3>and Ti<Ni_3>.钛<Ni_3>是稳定的，其他的都是可过渡的阶段。一种精细和分散的精确度<Ti_3>，<Ni_4>由于相干的谷物边界造成了全轮形状记忆效应。这种影响在较大的违规者成长的情况下不会出现。它<Ti_3>是一个<Ni_4>rhombohedral结构（a=6.72 &lt;!）A&gt; ，<alpha>=113.9）与有序原子安排。lenticular precipitate<Ti_3><Ni_4>has the anisotropy in both of inner （compression stress） side and outer （tension stress）side. 5。反对压力轴，<Ti_3>占主导地位的半个轴在<Ni_4>压缩方面和张力方面是绝对的，尊重。中间（R）阶段和麦芽（M）在特定冷却期间生成的阶段是最好的方便方向，即在父阶段和前齐位之间的内部应变，特别是在半质或前齐位轴的方向上，在半质或前齐位轴的方向上。因此，在R阶段的增长之后，R阶段的单个变体围绕Precipitate， Martensite阶段出现。由于晶格恒定的压缩压力侧延伸和张力压力侧收缩的结果在弯曲约束的物质中的差异。它包含了特殊变化的形状，以及在冷却期间出现的全圆形状记忆效应。

Ni rich TiNi alloys (Ti-51-52at%Ni) exhibit the all-Round Shape Memory Effect by aging under constrain. The aim of this research project is to clarify the mechanism of this All-Round Shape Memory Effect. Shape memory effects of Ti-51 and 52at%Ni specimens were investigasted under the various conditions of constrained aging by means of optical microscope and eleotron microscope. The results are as follows.1. The TTT diagrams of precipitates in this alloy were made between 300-600゜C. Precipitates were <Ti_3> <Ni_4> (precisely <Ti_11> <Ni_14> ), <Ti_2> <Ni_3> and Ti <Ni_3> . Ti <Ni_3> is stable and the others are metastable phases.2. Fine and dispersed precipitates of <Ti_3> <Ni_4> with coherent grain boundary cause the All-Round Shape Memory Effect. This effect does not appear in the case of bigger precipitates grown up.3. The crystal structure of <Ti_3> <Ni_4> is rhombohedral structure (a=6.72 <。!A> , <alpha> =113.9) with ordered atomic arrangement.4. The lenticular precipitate <Ti_3> <Ni_4> has the anisotropy in both of inner (compression stress) side and outer (tension stress) side.5. Against the stress axis, the semimajor axis of presipitate <Ti_3> <Ni_4> is perpendecular in the compression side and parallel in the tension side, respectively.6. The growth direction of intermediate (R) phase and martensite (M) phase which generate in specimen during cooling is the best convenient direction which accomodates the internal strain between parent phase and precipitates, especially the strain in the direction of semiminor axis of precipitate. Therefore, after the growth of R phase with single variant around precipitate, martensite phase appears. As the result ofthe difference of lattice constant the compression stress side elongates and the tension stress side shrinks in bending constrained specimen during cooling. It is concluded that the shape of the specimen changes spontaneously and the All-Round Shape Memory Effect appears during cooling.