The effect of milling time on the evolution of nanostructure, thermal stability, and magnetocaloric properties of (Ni0.50Fe0.50)70.5B17.7Si7.8Ti4

We report the evolution of nanocrystalline γ-Ni of 3-7 nm size along with amorphous phase in (Ni0.50Fe0.50)70.5B17.7Si7.8Ti4 (at.%) upon mechanical alloying of the elemental powder mixture up to 36 h. The effect of milling time on the nanostructure, thermal stability and magnetic properties, have been investigated using x-ray diffraction, differential scanning calorimeter, transmission electron microscope, and vibrating sample magnetometer. The lattice parameter of the γ-Ni phase gradually decreases from 0.3607 nm for 9 h milling down to 0.3554 nm upon 36 h of milling. A first-order magnetic transition has been identified using Arrott plot analysis at Curie temperature (TC) of 608 K along with a large magnetic entropy change (ΔSM) of 0.45 J/kg.K at an applied field of 13800 Oe, and relative cooling power (RCP) of 10.15 J/kg. The effects of nanostructure and phase constituents on the thermal stability, TC, magnetization and coercivity, have been correlated.