室温下Fe62Ni27Mn11（wt%）合金的压致fcc-hcp相变

 本文采用Mao-Bell型金刚石对顶砧（DAC）及高压在位（in situ）粉末X光衍射照相方法研究了Fe₆₂Ni₂₇Mn₁₁（wt%）合金在0~43.2 GPa压力范围内的压致结构相变和等温压缩行为，实验结果表明，该合金在低压时为fcc结构，在19.4 GPa压力附近出现压致fcc→hcp结构相变，直到43.2 GPa一直保持fcc、hcp二相共存；相变过程中，二相的molar体积相同；高压hcp相得晶格参数比值c/a基本上不随压力而变，可以表示为c/a=1.630±0.006；在卸压过程中，hcp相可保持到5.8 GPa，当卸压到常压时，该合金完全恢复到fcc结构；用Murnaghan等温固体状态方程对其压缩数据进行最小二乘法拟合，得到B₀=(166±12) GPa，B₀'=5.2±0.5；本文还给出了该合金的压致fcc→hcp结构相变模型，并对存在很宽的二相共存区间问题进行了初步探讨。

PRESSURE INDUCED fcc-hep PHASE TRANSITION OF Fe_(62)Ni_(27)Mn_(11)(wt%) ALLOY AT ROOM TEMPERATURE

By using Mao-Bell type diamond anvil cell (DAC) and an in situ high pressure powder X-ray diffraction method, the pressure induced phase transition and the isothermal compression of Fe₆₂Ni₂₇Mn₁₁ (wt%) alloy were investigated at room temperature and high pressure up to 43.2 GPa. The crystal structure of this alloy is the fcc structure below 19.4 GPa. The pressure induced fcc→hcp phase transition occurs at 19.4 GPa, and then the fcc phase and the hcp phase coexisted up to 43.2 GPa with the same molar volume. The ratio of the lattice parameters of the hcp phase, c/a, keeps essentially a constant value of 1.630±0.006 in the present high pressure range of the experiments. In the course of unloading, the hcp phase will remain its existence down to 5.8 GPa, and then transforms completely to the fcc structure as it is release to atmospheric pressure. The Murnaghan isothermal equation of state for this alloy was fitted with the parameters B₀=(166±12) GPa, B₀'=5.2±0.5 by using the least-square method. A model for this pressure induced fcc→hcp phase transition is presented and the reason why it has so wide a two-phase-coexistence pressure region is also discussed.