Structure-Property Correlation of High Fe-Content Fe-B-Si-Hf Bulk Glassy Alloys

Fe-based amorphous alloys are well known for their good magnetic properties. But these alloys were only prepared into ribbon form in early times due to their insufficient glass-forming abilities GFAs). After first synthesized of Fe-(Al, Ga)-P-C-B bulk glassy alloy, many Fe- based bulk metallic glasses (BMGs) were synthesized. Compared with amorphous alloy ribbons, the GFA of these alloys was significantly improved, but the saturation magnetization (B-s) was less than 1.5 T. To achieve higher Bs in Febased amorphous alloys, the Fe content should be maximized and the metalloid and alloying elements contents should be minimized, but it makes glass formation difficult. It is difficult to reveal the effect mechanism of Fe atoms in high Fe- content amorphous alloys, due to the complexity of the amorphous structure. The present work focuses on explores the structure-property correlations of high Fe- content Fe-B-Si-Hf multi-component glassy alloys with an amorphous structure model. A series of high Fe- content alloys with the composition of [Si-B2Fe7.7Hf0.3] Fe+Fe-x (x= 0, 1.5, 2, 2.5 and 3) was produced by adding Fe atoms to the ideal cluster formula, which is based on the composition with the best glass-forming ability of [Si-B2Fe7.7Hf0.3] Fe ( Fe72.5B16.7Si8.3Hf2.5) for Fe-B-Si-Hf quaternary alloys. Liquid quench, thermal analysis and magnetic measurement results show that the critical rod size for glassy alloys gradually decreases from 2.5 mm to 1 mm as the number of Fe atoms increases from 0 to 2. The [Si-B2Fe7.7Hf0.3] Fe+ Fe-2 ( Fe76.4B14.3Si7.1Hf2.2) bulk glassy alloy has a high saturation magnetization of 1.58 T and a low coercive force of 2.8 A/m. The decreasing of the glass transition temperature, the thermal stability, the glass-forming ability and the Curie temperature with increasing Fe content in Fe-B-Si-Hf glassy alloys was evaluated using a"dual-cluster"({[Si-B2Fe7.7Hf0.3]+[Fe-Fe-14](x/15)} Fe) amorphous structure model. The result shows that the [ Fe-Fe-14] cluster from the alpha-Fe phase plays an important role in determining the properties change for this series high Fe- content Fe-B-Si-Hf glassy alloys.