Development of New Fe-based Shape Memory Alloy (Fe-Ni-Co-Ti Alloy)

1. Fe-Ni-Co-Ti合金经适当的奥氏体化处理后，产生一种完全孪晶的薄板马氏体。通过调整化学成分和热处理条件，薄板马氏体的热滞效应发生了很大的变化，无论热滞效应的大小，薄板马氏体都能产生理想的形状记忆效应。例如，Fe-33 Ni-10 Co-4 Ti合金在973 K等温时效18 ks时，形成Ms和Af温度低于室温的热弹性马氏体，并在77 K形变后加热至室温时产生完全的形状记忆效应。Fe-31 Ni-10 Co-3 Ti合金在873 K等温时效3.6ks时，出现了具有较大热滞后的薄板马氏体（即，Ms 200K，As 350K，Af 500K）。该试样在室温下为完全奥氏体，在Ms附近或以下温度变形后，加热到Af以上，显示出完全的形状记忆效应。 关于我们 当在室温下变形时，MEN几乎不显示形状记忆效应。然而，当试样一旦在零度以下冷却到液氮中以产生大量马氏体时，即使在室温下变形，也会发生几乎完全的形状记忆效应。研究发现，Fe-Ni-Co-Ti合金的形状记忆效应是一个特征，它通过改变热膨胀程度而在从低温到高温的宽温度范围内发生.在Fe-Ni-Co-Ti合金中加入B或Al可改善奥氏体等温淬火后的塑性。这是由于抑制了相沿着奥氏体晶界的析出.当Fe-33 Ni-10 Co-4 Ti合金中的热弹性马氏体在273 ~ 77 K之间热循环时，热滞后显著增大，Ms温度略有降低，Af显著增加。经过几次热循环后，Af温度升高至室温以上，即使加热至室温后仍保留一定量的马氏体。因此，形状恢复程度通过转变从100%降低到约60%。少

1. The properly ausaged Fe-Ni-Co-Ti alloys produce a thin plate martensite which is completely twinned. The thermal hysteresis of thin martensite is widely changed by the adjustment of chemical composition and the ausaged condition, and these thin plate martensites cause a perfect shape memory effect irrespective of the extent of the thermal hysteresis. For example, when Fe-33Ni-10Co-4Ti alloy is ausaged at 973K for 18ks, the thermoelastic martensite whose Ms and Af temperature are below room temperature is formed and the complete shape memory effect occurs during heating up to room temperature after deformation at 77 K. In the case of Fe-31Ni-10Co-3Ti alloy ausaged at 873K for 3.6ks, thin plate martensite with a large thermal hysteresis (i.e., Ms 200K, As 350K, Af 500K) is formed. This specimen which is fully austenitic at room temperature shows a complete shapememory effect when specimen is heated up above Af after the deformation at temperatures near or below Ms. The as-ausaged spec … More imen hardly exhibits the shape memory effect when deformed at room temperature. However, when the specimen is once subzero cooled to liquid nitrogen to produce a large amount of martensite, the almost complete shape memory effect occurs even by the deformation at room temperature. It has been found to be characteristic that the shape memory effect in Fe-Ni-Co-Ti alloys occurs over the wide temperature range from low temperature to high temperature by the change in the extent of thermal hysteresis.2. The ductility of austenite after ausaging is improved by the addition of B or Al to Fe-Ni-Co-Ti alloys. This is due to the suppression of precipitation of phase along austenite grain boundaries.3. When the thermoelastic martensite in Fe-33Ni-10Co-4Ti alloy is thermally cycled between 273K and 77K, the thermal hysteresis becomes markedly large, i.e., the Ms temperature is slightly decreased and the Af is markedly increased. After several thermal cycles, the Af temperature is raised above room temperature and the some amount of martensite remains even after the heating up to room temperature. Therefore, the degree of shape recovery is decreased from 100% to about 60% by the transformation. Less