Preparation And Properties Of NiFeGa Magnetic Shape Memory Alloys (MSMA)

Ni55Fe17.5Ga27.5-xSnx(x=0,0.5,1,2) and Ni55Fe,7.5Ga27.5-xNbx(x=0,0.5,1,1.5,2,3) magnetic shape memory alloys (MSMA) were prepared by Induction melting and copper-mold vacuum suction casting. The effect of alloy composition and heat treatment on micro structure、crystal structure、magnetic performance of alloys were investigated by optical microscopy (OM)、X-ray diffraction (XRD) and vibrating sample magnetometer (VSM).The major results as follows:1. The microscopic structures of Ni55Fe17.5Ga27.5-xSnx and Ni55Fe17.5Ga27.5-xNbx alloy are related to the content of Sn and Nb. With the increase of the content of Sn (0～2at.%), martensite content in alloy decreased significantly. Without Sn addition, Alloy is composed of a large number of martensite phase and y phase; when the Sn content is2at.%, Alloy is composed of austenite phase only. With the increase of the content of Nb (0～3at.%), martensite volume decreased slightly in the Alloy, and the width of martensite variants becomes narrow. Without added Nb, Alloy is composed of martensite phase and y phase; when the Nb content is3at.%, Alloy are martensite phase, austenite phase, y phase coexistence.2. The saturation magnetization of Ni55Fe17.5Ga27.5-xSnx alloys is related to the content of Sn and heat treatment conditions. The saturation magnetization of alloy decreases with the increase of the content of Sn,The saturation magnetization of Ni55Fe17.5Ga27.5alloy as-cast is22.85emu/g; After add2at.%Sn, The saturation magnetization of alloy decreased to9.91emu/g. In the range of673K-1273K, with the increase of quenching temperature increasing, the saturation magnetization of the alloy increases.When quenched at673K, the saturation magnetization of Ni55Fe17.5Ga26.5Sn1alloy is13.89emu/g; when quenched at1273K, The saturation magnetization of alloy is18.02emu/g.3. The saturation magnetization of Ni55Fe17.5-xGa27.5Nbx alloys is related to the content of Nb and heat treatment conditions. The saturation magnetization of alloy decreases with the increase of the content of Sn. Quenched at1073K,thc saturation magnetization of Ni55Fe17.5Ga27.5alloy is24.8emu/g; After add3at.%Nb, the saturation magnetization of alloy decreases to12.48emu/g. In the range of673K-1273K, with the increase of quenching temperature increasing, the saturation magnetization of alloy increases. Quenched at673K, the saturation magnetization of Ni55Fe16Ga27.5Nb1.5alloy is14.03emu/g; At1273K, The saturation magnetization of alloy is24.26emu/g.4.The microscopic structures and saturation magnetization of Ni-Fe-Ga-X(X=Zn, Sb, Cr) alloys are related to addition element. Add Zn, Sb, Cr elements of the alloy,martensite content reduced in different degrees, saturation magnetization of alloy has decreased in different degree, quenched at1273K, Ni55Fe17.5Ga27.5alloy is composed of martensite phase, γ phase, saturation magnetization is24.79emu/g; add1at.%Cr alternative Fe, alloy make into the main phase of austenite, martensite phase, the saturation magnetization decreased to15.56emu/g.5.At the same quenching temperature, the saturation magnetization of Ni-Fe-Ga-Nb alloy increased slightly with the increase of the holding time. Quenched at1273K, for1h, The saturation magnetization of Ni55Fe17Ga27.5Nb0.5alloy is20.21emu/g; for4h,The saturation magnetization of alloy is21.23emu/g.6.The curie temperature of Ni55Fe17.5Ga27.5-xSnx alloy and Ni55Fe17.5-xGa27.5Nbx alloy are related to the content of Nb、Nb. The Curie temperature of Ni55Fe175Ga27.5-xSnx alloy decreases with the increase of content of Sn. Quenched at1273K, The curie temperature of Ni55Fe17.5Ga27.5alloy is461K; When add2at.%of the Sn, the Curie temperature of the alloy is decreased to444K. The Curie temperature of Ni55Fe17.5-xGa27.5Nbx alloys is different with the different content of Nb.When quenched at1273K, the curie temperature of Ni55Fe16.5Ga27.5Nb1is489K.7. Microstructure of Ni-Fe-Ga-Nb alloys is related to heat treatment conditions. In the range of673K-1273K, The content of the martensite increases as the quenching temperature. Quenched at673K, a small amount of martensite existed in Ni55Fe17.5Ga27Nb0.5alloy; Quenched at1273K,alloy is mainly composed of martensite phase. At the same quenching temperature, the content of martensite in the alloy increases with increasing of the holding time. When quenched at1273K for3h, alloy is almost entirely composed of martensite phase composition.