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The microstructures and magnetic properties of bulk Fe73Ga27 and Fe73Ga18V9 (at.%) ferromagnetic shape memory (FSM) alloys were investigated by transmission electron microscopy (TEM), a magnetostrictive-meter setup, and a superconducting quantum interference device magnetometry. Results showed that in the Fe73Ga27 FSM alloy solution treated (ST) at 1100 °C for 4 h and quenched in ice brine, the antiphase boundary segments (APBs) of the D03 domain were in the A2 (disordered) matrix and the Fe73Ga27 FSM alloy had an optimal magnetostriction and a higher magnetostrictive susceptibility ( \Delta \lambda^s\| \Delta {H} ). In Fe73Ga27 FSM alloy ST, aged at 700 °C for 24 h and furnace cooled (7 HTFC), D03 nanoclusters underwent phase transformation to an intermediate tetragonal phase (i.e., L10 -like tetragonal martensite) via Bain distortion, and finally L12 (Fe3Ga) structures precipitated, as observed by TEM. The L10 -like tetragonal martensite and L12 phases in the aged Fe73Ga27 FSM alloy drastically decreased the magnetostriction from positive to negative. However, by adding V into the Fe73Ga27 alloy system to produce Fe73Ga18V9 FSM alloy ST and ageing at 7 HTFC, the phase transformation of D03 to an intermediate tetragonal martensite phase and precipitation of L12 structures were not found. The results indicate that the aged Fe73Ga18V9 FSM alloy maintained stable magnetostriction. However, the addition of V into the Fe73Ga27 alloy system to produce Fe73Ga18V9 does not result in a higher saturation magnetization ( Ms ) or magnetocrystalline anisotropy energy constant ( Ku ) in the Fe73Ga18V9 FSM alloy. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy (TEM), a magnetostrictive-meter setup, and a superconducting quantum interference device magnetometer were used to investigate the microstructures, saturation magnetostriction, and magnetic properties of bulk Fe81Ga19 and Fe73Ga19Ni8 (at. %) ferromagnetic shape memory alloys (FSMAs). In the Fe81Ga19 FSMA, after solution treatment (ST) at 1100 °C for 4 h and quenching in ice brine, the antiphase boundary segments of the D03 domain were observed in the A2 (disordered) matrix. When the Fe81Ga19 FSMA was solution treated and aged at 750 °C for 24 h and then furnace cooled (FC), the A2 + D03 phase transformed into A2 + B2 + D03 structures, accompanied by coarse B2 + D03 precipitates in the A2 matrix. This result decreased the saturation magnetostriction of the aged Fe81Ga19 FSMA. However, adding more Ni to the Fe81-xGa19Nix (x = 8 at. % Ni) FSMAs enhanced the formation of B2 + D03 structures, further decreased the saturation magnetostriction, and destroyed the ferromagnetic shape memory effect in Fe73Ga19Ni8 FSMA ST, aged at 750 °C for 24 h, and FC. [ABSTRACT FROM AUTHOR]