Effects of Si and Mo additions on glass-forming in $\mathrm{FeGaPCB}$ bulk glassy alloys with high saturation magnetization

We investigated the effect of Si and Mo additions on the glass-forming ability (GFA) of $\mathrm{Fe}\text{−}\mathrm{Mo}\text{−}\mathrm{Ga}\text{−}\mathrm{P}\text{−}\mathrm{C}\text{−}\mathrm{B}\text{−}\mathrm{Si}$ alloys. The simultaneous addition of small amounts of Si and Mo was found to be effective for extension of the supercooled liquid region $\left(\mathrm{\Delta }{T}_x\right)$ defined by the difference between glass transition temperature $\left(T_g\right)$ and crystallization temperature $\left(T_x\right)$. The $\mathrm{\Delta }{T}_x$ value is $26\mathrm{K}$ for the ${\mathrm{Fe}}_{78}{\mathrm{Ga}}_2{\mathrm{P}}_{12}{\mathrm{C}}_4{\mathrm{B}}_4$ glassy alloy, and increases to 52 and $50\mathrm{K}$ for the ${\mathrm{Fe}}_{76}{\mathrm{Mo}}_2{\mathrm{Ga}}_2{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ and ${\mathrm{Fe}}_{74}{\mathrm{Mo}}_4{\mathrm{Ga}}_2{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ glassy alloys, respectively. Similarly, the $\mathrm{\Delta }{T}_x$ value is $33\mathrm{K}$ for the ${\mathrm{Fe}}_{77}{\mathrm{Ga}}_3{\mathrm{P}}_{12}{\mathrm{C}}_4{\mathrm{B}}_4$ glassy alloy, and increases to 60 and $57\mathrm{K}$ for the ${\mathrm{Fe}}_{75}{\mathrm{Mo}}_2{\mathrm{Ga}}_3{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ and ${\mathrm{Fe}}_{73}{\mathrm{Mo}}_4{\mathrm{Ga}}_3{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ glassy alloys, respectively. These four glassy alloys also exhibit rather high reduced glass transition temperature $(T_g∕T_l)$ of 0.58–0.60. By copper mold casting, bulk glassy alloy rods with the diameters of 1.5 to $2.5\mathrm{mm}$ were prepared. These four glassy alloys also exhibit high saturation magnetization $\left(I_s\right)$ of $1.11–1.32\mathrm{T}$ and good soft-magnetic properties, i.e., low coercive force $\left(H_c\right)$ of $2.4–3.3\mathrm{A}∕\mathrm{m}$, and high effective permeability $\left({\mu }_e\right)$ at $1\mathrm{kHz}$ of $8500–14000$. The relation between crystallization behavior and GFA was also investigated. It was found that the primary precipitation phase of the $\mathrm{Fe}\text{−}\mathrm{Mo}\text{−}\mathrm{Ga}\text{−}\mathrm{P}\text{−}\mathrm{C}\text{−}\mathrm{B}\text{−}\mathrm{Si}$ glassy alloys is a complex fcc $(\mathrm{Fe},\mathrm{Mo}{)}_{23}(\mathrm{B},\mathrm{C}{)}_6$ phase, and the addition of small amounts of Si and Mo is effective for the suppression of precipitation of $(\mathrm{Fe},\mathrm{Mo}{)}_{23}(\mathrm{B},\mathrm{C}{)}_6$ phase, resulting in the extension of $\mathrm{\Delta }{T}_x$ and the improvement of GFA.

Figure 1

DSC curves of melt-spun ${\mathrm{Fe}}_{78}{\mathrm{Ga}}_2{\mathrm{P}}_{12-x}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_x$ ($x=1.5$, 2, 2.5 and 3) glassy alloys.

Figure 2

DSC curves of melt-spun ${\mathrm{Fe}}_{78-x}{\mathrm{Mo}}_x{\mathrm{Ga}}_2{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ ($x=1$, 2, 4, and 6) glassy alloys.

Figure 3

DSC curves of melt-spun ${\mathrm{Fe}}_{77-x}{\mathrm{Mo}}_x{\mathrm{Ga}}_3{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ ($x=1$, 2, 4, and 6) glassy alloys.

Figure 4

XRD patterns of the cast ${\mathrm{Fe}}_{76}{\mathrm{Mo}}_2{\mathrm{Ga}}_2{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ rod with a diameter of $2\mathrm{mm}$ and ${\mathrm{Fe}}_{75}{\mathrm{Mo}}_2{\mathrm{Ga}}_3{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ rods with diameters of 2 and $2.5\mathrm{mm}$, together with the XRD patterns of the melt-spun glassy alloy ribbons with a thickness of $20\mathrm{\mu }\mathrm{m}$.

Figure 5

DSC curves of the ${\mathrm{Fe}}_{76}{\mathrm{Mo}}_2{\mathrm{Ga}}_2{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ glassy rod with a diameter of $2\mathrm{mm}$ and ${\mathrm{Fe}}_{75}{\mathrm{Mo}}_2{\mathrm{Ga}}_3{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ glassy rods with diameters of 2 and $2.5\mathrm{mm}$. The DSC curves of the melt-spun glassy alloy ribbons are also shown for comparison.

Figure 6

XRD patterns of the ${\mathrm{Fe}}_{75}{\mathrm{Mo}}_2{\mathrm{Ga}}_3{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ glassy alloy subjected to annealing for $600\mathrm{s}$ at temperatures of 760 and $830\mathrm{K}$. The XRD pattern of the as-quenched alloy is also shown for comparison.

Figure 7

XRD patterns of the ${\mathrm{Fe}}_{71}{\mathrm{Mo}}_6{\mathrm{Ga}}_3{\mathrm{P}}_{10}{\mathrm{C}}_4{\mathrm{B}}_4{\mathrm{Si}}_2$ glassy alloy subjected to annealing for $600\mathrm{s}$ at temperatures of 783, 825, and $868\mathrm{K}$. The XRD pattern of the as-quenched alloy is also shown for comparison.