Effects of Ni addition on the magnetostriction and microstructures of Fe_(70-x)Pd_(30)Ni_x high-temperature ferromagnetic shape memory alloys

摘要

This study investigated the effects of adding a third alloying element, Ni, to create Fe_(70-x)Pd_(30)Ni_x (x = 2, 4, 6, and 8 at. % Ni) ferromagnetic shape memory alloys. The Ni replaced a portion of the Fe. The magnetostriction and microstructures of Fe_(70-x)Pd_(30)Ni_x high-temperature ferromagnetic shape memory alloys were studied in detail. Investigation of the magnetostriction and microstructures indicated that the greater Ni amount in the Fe_(70-x)Pd_(30)Ni_x alloys caused the less saturation magnetostriction at room- temperature (RT); it was also observed that it was more difficult to generate an annealed recrystallization. However, greater Ni addition into the Fe_(70-x)Pd_(30)Ni_x (x = 6 and 8 at. % Ni) alloys, the L1_0 + L1_m twin phase decomposition into stoichiometric L1_0 + L1_m + α_(bct) structures could be suppressed when the alloys were aged at 500 ℃ for 100 h. The result was that the Fe_(70-x)Pd_(30)Ni_x (x = 6 and 8 at. % Ni) alloys maintained a high magnetostriction and magnetostrictive susceptibility (Δλ_(||)~s/ΔH) after the 500℃/100h aged treatment. This magnetic property of the Fe_(70-x)Pd_(30)Ni_x (x = 6 and 8 at. % Ni) alloys is suitable for application in a high temperature (T> 500 ℃) and high frequency environment.