Ni-Fe-Ga-Co磁性记忆合金微观组织与力学行为

Microstructure and Mechanical Properties of Ni-Fe-Ga-Co Ferromagnetic Shape Memory Alloys

系统研究Ni-Fe-Ga-Co磁性形状记忆合金的显微组织结构以及力学行为,阐明掺Co对NiFeGa合金中γ相析出的影响规律,探明γ相增韧的微观机制。结果表明,铸态Ni-Fe-Ga-Co合金室温组织由马氏体和γ相两相组成,γ相数量随Co含量增加而增多。Fe和Co原子在马氏体相中存在最大饱和浓度,当二者含量之和超过16at%时,剩余的Fe和Co原子以γ相形式析出。γ相为富Fe和Co而贫Ga相,且Fe和Co原子的最大饱和浓度约为23at%。合金的屈服强度和断裂强度随Co含量增多呈增大趋势。断口观察发现,基体相为解理断裂,小尺寸的γ相被裂纹绕过或被整体拔出,大尺寸的γ相被拉长、撕裂或整体拔出,说明γ相有利于改善合金韧性,但增韧效果受到γ相尺寸的影响。

The microstructure and mechanical properties of Ni56Fe17Ga27-xCox（x=0, 2, 4, 6） magnetic shape memory alloys have been studied, and the influence of Co addition on γ, phase and the mechanism for increasing toughness by γ phase were revealed. The results show that the microstructure of as-melted alloys is composed of martensite phase and γ, phase at room temperature. With increasing Co content, the volume of γ, phase increases. For the martensite phase, the saturation solubility of Fe and Co atoms is fixed. If the total content of Fe and Co atoms exceeds 16 at %, the residual atoms will exist in the form of γ, phase, which is rich in Fe and Co atoms. Besides, the saturation solubility of Fe and Co atoms in γ phase is around 23 at %. The tensile tests show that the yielding strength and fracture strength increase with increasing Co content. The fracture mechanism of martensite phase is transcrystalline fracture, and the γ phase is gliding fracture, it proves that the γ, phase improves the toughness of experimental alloys.