Thermal stability, crystallization behavior, Vickers hardness and magnetic properties of Fe-Co-Ni-Cr-Mo-C-B-Y bulk metallic glasses

Thermal stability, crystallization behavior, Vickers hardness and magnetic properties of the Fe41Co7-xNixCr15Mo14C15B6Y2 (x=0, 1, 3, 5) bulk metallic glasses were investigated. The Fe41Co7-xNixCr15Mo14C15B6Y2 (x=0, 1, 3, 5) metallic glasses were fabricated by copper mold casting method. The thermal stability and crystallization behavior of the metallic glass rods were investigated by differential scanning calorimetry and isothermal experiments. Hardness measurements for samples annealed at different temperatures for different time were carried out at room temperature by the Vickers hardness tester, and magnetic measurements were performed at different temperatures by the vibrating sample magnetometer. It is shown that the addition of Ni does not play a positive role for enlarging ΔTx and GFA from parameter γ (=Tx/(Tg+Tl)), and it can, however, increase the activation energy in the initial stage of crystallization by changing the initial crystallization behavior. The minor addition of Ni can refine the crystal grain obtained from the full crystallization experiment. The primary crystallization causes the decrease of hardness in these alloys, and as the crystallization continues, the hardness in all samples increases instead due to the precipitation of carbide and boride. The annealing temperature has an obvious effect on magnetic properties of these alloys, and the minor addition of Ni can effectively prevent the alloy annealed at high temperature to transform from paramagnetic to ferromagnetic state.