| Magnetrictive material is a kind of new type of functional material, which exhibits many outstanding advantages and is widely applied in avigation, spaceflight, navigation, atuomanto, and energy sources domains. Now they have been used to design and fabricate many intelligent devices such as active vibration absorbers, linear motors, micro-pumps, micro-valves, and micro-positioners etc.Fe–Ga alloy, as a kind of new magnetostrictive material, was concentrated by people in recent years because it has high mechanical strength, good ductility, large magnetostriction at low saturation magnetic fields, negligible magnetic hysteresis, and lower associated cost relative to the materials of Tb-Dy-Fe. Moreover, Galfenol have an appreciable tensile strength and good ductility.In this paper we will mainly focus on the study on the physical properties of Galfenol magnetostrictive alloy and discuss the reason of large magnetostriction. We also try to improve the magnetostrictive, mechanical, and other physical properties of Galfenol. All the contents are as following.Study on intrinsically increasing the electrical resistivity without magnetostriction greatly deteriorated in Fe-Ga alloys currently keeps open and attractive. So we present the results of the effects of Mn-doping on the structure, electrical resistivity, the magnetostriction, and Curie temperature of Fe-Ga alloys. Both high electrical resistivity and even enhanced magnetostrictive properties were obtained in the Fe-Mn-Ga alloys. It may make the Fe-Ga alloys become very attractive candidate materials for magnetic actuator applications. We also present the effects of Mn-doping on the structure, electrical resistivity, and the magnetostriction of Fe-Al alloys. Though high electrical resistivity was obtained but magnetostrictive properties were greatly deteriorated in the Fe-Mn-Al alloys.In practical application, a large and linear magnetostriction is expected in Fe-Ga alloys. On the other hand, it is also important to investigate the effect of the coupled magneto-mechanical loading on magnetostriction and compressive strain of Fe-Ga alloys. A shift from negative value to positive value in magnetostriction was observed with increasing compressive stress in Fe85Ga15 single crystal. The nonlinear behavior of the compressive strain in different magnetic fields was observed during the compressive loading and unloading process. A model based on the magnetic-domain switching process can clearly explain these phenomena.In view of applications, proper alignment of the magnetic moments is very important. For getting full strain performance, a post-growth treatment process is indispensable. Due to the longitudinally solidified crystal grains in the textured rod, the magnetocrystalline anisotropy and the shape anisotropy are both in the growth direction. Thus, an optimal treatment should use tensile stress during the post-growth process to align the magnetic moments in this direction. A novel tensile-stress heat-treatment method has been used for textured polycrystalline rods and a large magnetostriction up to 200 ppm has been obtained in an alloy with composition Fe83Ga17 without application of pre-stress. It also makes that as much as about 90% of the total magnetostriction can be adjusted by stress.Due to the complete alignment of the magnetic moments, a magnetostrictive contribution of the BCC(A2) phase can be ruled out and the magnetostrictive behavior of the Fe3Ga(DO3) phase has been investigated in detail. We also make some other Fe based magnetostriction alloys by way of doping and study their magnetic properties. The related physics is complex which requires a further fundamental investigation.
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