STRUCTURAL AND MAGNETIC PROPERTIES OF Fe–Co/Al₂O₃ NANOCOMPOSITE POWDER PRODUCED BY MECHANICAL ALLOYING

Abstract

The effect of milling time and addition of elements on the microstructure, magnetic and mechanical properties of the Fe–xCo (x = 0, 5, 10, and 20 wt.%) matrix nanocomposite reinforced with 40 wt.% Al₂O₃ during mechanical alloying is examined. Fe–Al₂O₃ and Fe–Co–Al₂O₃ alloys are milled for 5, 15, 20, 30 and 20 h, respectively. The balance between the welding and fracturing and a steady-state situation is found out in the Fe–Co–40 wt.% Al₂O₃ nanocomposite after 20 h, due to the Co introduction into the Fe matrix, but not in the Fe–Al₂O₃ nanocomposite. After 30 h of milling, the average crystallite size was 5 nm in the Fe matrix. The lattice strain increased to ~0.64% in the Fe matrix after ≤30 h of milling and in the binary Fe–20 wt.% Co matrix after 20 h of milling; the average crystallite size was 3 nm. The lattice strain increased to ~0.56% for the Fe–20 wt.% Co matrix after ≤20 h of milling. The coercive field (H_c) increased from 6.407 to 82.027 Oe, while the saturation magnetization (M_s) decreased from 20.732 to 15.181 emu/g in the Fe matrix during milling. The H_c and M_s are maximum for the binary matrix (20 and 10% Co, respectively).