Fig. 1. The goal of this work was to increase the heat transfer coefficient and thus the cooling rate by developing novel cooling strategies during molten metal gas atomization. Gas atomization (GA) with conventional cooling, spray cone cooling (GA + SCC), and liquid quenching (GA + LQ) were used in this study. Both cooling techniques used distilled water as a cooling medium. Spray cone cooling used distilled water to cool the spray cone from all angles, whereas liquid quenching was performed to quench the molten droplets. Experimental details are listed in Supplementary Material.

Fig. 2. XRD analyses for {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 powders using different cooling strategies.

Fig. 3. XRD analyses for Fe76B10Si9P5 powders using different cooling strategies.

Fig. 4. DSC analyses on (a) {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 and (b) Fe76B10Si9P5 powders for two different particle size classes (25-45 μm and 125-150 μm). The abbreviations GA, GA + SCC, and GA + LQ stand for conventional gas atomization, conventional gas atomization and spray cone cooling, and conventional gas atomization and liquid quenching, respectively (see Fig. 1).

Fig. 5. Enthalpy of crystallization describing the amorphous fraction as a function of particle diameter. (a) {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 and (b) Fe76B10Si9P5 soft ferromagnetic glass-forming alloys were considered for gas atomization with conventional cooling and the different cooling strategies. The {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 alloy was additionally quenched in poly(ethylene glycol) (PEG). The horizontal error bars represent the d16,3 and d84,3 percentiles measured by particle laser diffraction. Measurements on melt spinning (MS) samples were also plotted for comparison. The dashed line refers to the average enthalpy of crystallization and the upper and lower edges of the orange area defines the upper and lower standard deviation. The abbreviations GA, GA + SCC, and GA + LQ stand for conventional gas atomization, conventional gas atomization and spray cone cooling, and conventional gas atomization and liquid quenching, respectively (see Fig. 1).

Fig. 6. Hydrogen and oxygen measurements for {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 and Fe76B10Si9P5 powders. Different particle size classes were considered.

Fig. 7. Saturation magnetization determined from vibrating sample magnetometer measurements as a function of particle size for (a) {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 and (b) Fe76B10Si9P5 powders. Conventional gas atomization and novel cooling strategies were considered for this study. Measurements on melt spinning samples (MS) were also plotted for comparison (the dashed line refers to the average saturation magnetization and the upper and lower edges of the orange area defines the upper and lower standard deviation).

Fig. 8. Saturation magnetization determined from B-H curve tracer measurements as a function of two particle size classes (< 25 μm and 25-45 μm) for (a) {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 and (b) Fe76B10Si9P5 as-atomized powders, as well as sintered toroidal rings. The toroidal rings had an outer and inner diameter of 13 and 8 mm as well as a height of 2.6 ± 0.15 mm. Conventional gas atomization and novel cooling strategies were considered for this study. Measurements on melt spinning samples (MS) were also plotted for comparison (the dashed line refers to the average saturation magnetization and the upper and lower edge of the orange area defines the upper and lower standard deviation). The abbreviations GA, GA + SCC, and GA + LQ stand for conventional gas atomization, conventional gas atomization and spray cone cooling, and conventional gas atomization and liquid quenching, respectively (see Fig. 1).

Fig. 9. Coercivity (a) and permeability (b) of sintered toroidal rings for two soft ferromagnetic glass-forming alloys ({(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 and Fe76B10Si9P5). The rings had an outer and inner diameter of 13 and 8 mm as well as a height of 2.6 ± 0.15 mm. Two particle size classes were used to consolidate the powders (< 25 μm and 25-45 μm). The abbreviations GA, GA + SCC, and GA + LQ stand for conventional gas atomization, conventional gas atomization and spray cone cooling, and conventional gas atomization and liquid quenching, respectively (see Fig. 1).