Novel phase decomposition, good soft-magnetic and mechanical properties for high-entropy (Fe0.25Co0.25Ni0.25Cr0.125Mn0.125)100–B (x = 9–13) amorphous alloys

Abstract

Abstract As-spun (Fe0.25Co0.25Ni0.25Cr0.125Mn0.125)100–xBx (x = 9–13 at%) alloys are fully amorphous with bending plasticity and good soft-magnetic properties. Manganese addition favors amorphous phase formation at lower B content than in comparable alloys. On heating, the alloys transform: [am] → [am’ + bcc + fcc] → [fcc] at 9–11% B; and [am] → [am’ + bcc + fcc] → [bcc + fcc + borides] → [fcc + borides] at 12–13% B. Novel observations are the formation of metastable bcc + fcc phases, and an endotherm due to the [bcc + fcc] → [fcc] transition. The Vickers hardness of 9–11% B alloys is ∼650 in the as-spun state, shows a maximum of 1010 for [bcc + fcc] state and then decreases to 750 upon transition to [fcc]. As-cast 9–11% B 2-mm-diameter rods, mainly [bcc + fcc], exhibit compressive strength of 1520–1705 MPa and plastic strain >25%. These high-strength alloys, and the as-spun amorphous alloys with soft-magnetic properties, are encouraging for the further development of structural and functional materials.