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

摘要:

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16 at%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23 at%。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

Abstract:

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