Fe-Ni-Co-Ti 铁磁形状记忆合金的沉淀相变和成分设计

Fe-Ni-Co-Ti alloys have received attention for its potential magnetically induced shape memory effect (MISME) with high output power since its saturation magnetization is 3 times of well-investigated Ni-Mn-Ga. The thin plate martensite with glissile interface at room temperature is critical for promising MISME. Present study is concerning on optimizing composition and ausageing technique to obtain the thin-plate-martensite at room temperature through the adjustment of transformation temperature and matrix strength. Morphology of martensite in different composition and ageing process were presented and the influence of component in alloy was investigated. Hardness and MS temperature are also tested as a function of ageing time with precipitation transformation. Results show that nickel is the sensitive element on morphologies of martensite and MS temperature. With Ni content of 29~32wt% and appropriate aging treatment, the thin plate martensite could be obtained at room temperature. Ti plays an important role in improving hardness in the process of precipitation, while Co accelerates the Ni3Ti precipitate. The impact of precipitation on martensitic transformation is also discussed.