Structural Analysis and Magnetic Properties of FeCo Alloys Obtained by Mechanical Alloying

Abstract

A systematic study on the structural and magnetic properties of F e 100 - x C o x alloys ( 10 < x < 90 , Δ x = 10 in wt. percent) obtained by mechanical alloying is presented. Elemental powders of Fe and Co mixed in an adequate weight ratio were milled at room temperature in a shaker mixer mill using vials and balls of hardened steel as milling media with a ball : powder weight ratio of 12 : 1. The mixtures were milled for 3 h. The results show that, after milling, for almost all the composition (up to x = 60 ), solid solutions based on bcc structures were obtained. For Co-rich alloys ( x ≥ 70 ), different phases were found, revealing the formation of a metastable intermetallic phase (FeCo, wairauite) together with fcc-Co and hcp-Co phases. The specific saturation magnetization increases by increasing Co content, reaching a maximum value of 225 emu/g for hcp-Fe 70 Co 30 , and then it shows a diminution up to 154 emu/g for bcc-Fe 30 Co 70 . All studied alloys ( F e 100 - x C o x ) present low coercivity, in the range from 0 to 65 Oe, which is lower than reported. The coercivity increases with the increment in Co, reaching a maximum of 64.1 Oe for Fe 40 Co 60 . After that, the coercivity falls up to 24.5 Oe for Co-rich alloys, which make them a very low coercive material.