Effects of Ni addition on the magnetostriction and microstructures of Fe70−xPd30Nix high-temperature ferromagnetic shape memory alloys

Abstract

This study investigated the effects of adding a third alloying element, Ni, to create Fe70−xPd30Nix (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 Fe70−xPd30Nix high-temperature ferromagnetic shape memory alloys were studied in detail. Investigation of the magnetostriction and microstructures indicated that the greater Ni amount in the Fe70−xPd30Nix 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 Fe70-xPd30Nix (x = 6 and 8 at. % Ni) alloys, the L10 + L1m twin phase decomposition into stoichiometric L10 + L1m + αbct structures could be suppressed when the alloys were aged at 500 °C for 100 h. The result was that the Fe70−xPd30Nix (x = 6 and 8 at. % Ni) alloys maintained a high magnetostriction and magnetostrictive susceptibility (Δλ‖s/ΔH) after the 500 °C/100 h aged treatment. This magnetic property of the Fe70−xPd30Nix (x = 6 and 8 at. % Ni) alloys is suitable for application in a high temperature (T > 500 °C) and high frequency environment.