ⓒ 2012 Journal of Magnetics Effects of Ni Addition on the Microstructures and Magnetic Properties of Fe70-xPd30Nix High-Temperature Ferromagnetic Shape Memory Alloys

This study investigated the effects of adding a third alloying element, Ni, to create Fe70-xPd30Nix (x = 2, 4, 6, 8 at. % Ni) ferromagnetic shape memory alloys (FSMAs). The Ni replaced a portion of the Fe. The Fe70-xPd30Nix alloys were homogenized through hot and cold forging to gain a ~38 % reduction in thickness, next they were solution-treated (ST) with annealing recrystallization at 1100 oC for 8 h and quenched in ice brine, and then aged at 500 oC for 100 h. Investigation of the microstructures and magnetostriction indicated that the greater Ni amount in the Fe70-xPd30Nix alloys reduced saturation magnetostriction at room temperature (RT). It was also observed that it was more difficult to generate annealed recrystallization. However, with greater Ni addition into the Fe70-xPd30Nix (x = 6, 8 at. % Ni) alloys, the L10+L1m twin phase decomposition into stoichiometric L10+L1m+αbct structures was suppressed after the 500 oC/100 h aging treatment. The result was that the Fe70-xPd30Nix (x = 6, 8 at. % Ni) alloys maintained a high magnetostriction and magnetostrictive susceptibility (Δλ|| s/ΔH) after the alloys were aged at 500 oC for 100 h. This magnetic property of the Fe70-xPd30Nix (x = 6, 8 at. % Ni) alloys make it suitable for application in a high temperature (T> 500 oC) and high frequency environ-ments