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

As-spun (Fe0.25Co0.25Ni0.25Cr0.125Mn0.125)(100-x)B-x (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 similar to 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. (C) 2020 The Authors. Published by Elsevier B.V.