Formation of non-equilibrium phase by leaching of rod-milled Al0.6(Co50Cu50)0.4 alloy powders

Abstract

We report upon the formation of non-equilibrium phase by leaching of Al 0.6 (Co 50 Cu 50 ) 0.4 alloy powders produced by rod milling. X-ray diffractometry (XRD), scanning electron microscopy, differential scanning calorimetry, transmission electron microscopy, and vibrating sample magnetometry were used to characterize the as-milled and leached specimens. After 400 h of milling, bcc type peaks of the intermetallic compound AlCo were present in the XRD pattern. Leaching of the Al from the as-milled powders did not induce any significant change in the diffraction pattern. After annealing the leached specimen at 500 °C for 1 h, the nanoscale crystalline phase was transformed into the fcc Cu phase, and this was accompanied by a change in the magnetic properties. Magnetization decreased gently on heating from room temperature to 189.0 °C, then increased suddenly with temperature rising to 514.0 °C, as the Co and Cu atoms were rearranged, and finally decreased gently as heating continued to 800 °C. On cooling the specimen from 800 °C, the magnetization increased gently. The Curie temperature was about 564.2 °C for the as-milled powders.