采用液态金属冷却定向凝固方法制备出Co-Ni-Ga取向晶体, 并研究了不同晶体生长速度下, 晶体的轴向择优取向及其定向凝固组织的变化. 结果表明: 在温度梯度为250 K/cm、晶体生长速度为0.9 mm/min时, 柱晶具有完全的<110>取向, 存在单变体马氏体并有麦穗状'相析出;当生长速度提高至9 mm/min时, 合金试样为<111>+<001>+<110>混合取向, 凝固组织转变为单一的马氏体板条. EDS表明, 定向晶体沿稳定生长区轴向成分比较均匀, 无明显宏观偏析存在. 采用此方法能够获得比较长的稳定的马氏体单变体区, 为制备铁磁形状记忆合金取向多晶材料提供了新思路.
The directionally solidified Co-Ni-Ga ferromagnetic shape memory alloys were prepared by liquid metal cooling method. The preferred orientation and microstructure evolution of crystals under different growth velocity were investigated. The results indicate that keeping the temperature gradient GL=250K/cm, when the growth velocity was 0.9mm/min, a preferred orientation <110> was obtained and the worm-like second phase γ′ precipitated in the martensite matrix which was found to be coarsening along the solidification direction; While the growth velocity was increased to 9mm/min, a <110>+ <001>+<211> mixed orientation was obtained, and the single martensite phase was observed in this case. No obvious macro-segregation was detected based on the results of energy dispersive spectrometer. The paper proposes a new method to fabricate the ferromagnetic shape memory polycrystals with preferred orientation.
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