Evolution of a FeV sigma phase ball-milled in a mixture of argon and air

Abstract

A coarse-grained sigma phase Fe48.1V51.9 was ground in argon in a vibratory mill in the presence of a small but steady air supply. The oxygen content increases regularly at a rate of about 0.25 at.%/h. During the first 140 h of milling, the sigma phase transforms into a heterogeneous bcc alpha phase because of a preferential oxidation of the sole vanadium atoms into V2O3. At that milling time, the average composition of the remaining bcc alloy is ~Fe80V20. Mossbauer spectroscopy shows too the presence of an amorphous phase. For longer milling times, ternary Fe–V–O spinel phases do form.