AMORPHIZATION OF AL-CR ATOMIZED POWDER BY MECHANICAL GRINDING

Faster amorphization of the Al-Cr system has been investigated by the use of atomized powders as a starting powder for mechanical grinding ( MG). The MG of both as-atomized and fully heat-treated (at 1173 K for 1 h) Al-20mol.%Cr powders was performed using a vibration mill. For th e MG of as-atomized powders, an amorphous phase was very easily obtain ed after only 10 h vibration milling. The amorphous phase crystallized into an equilibrium delta phase at about 860 K when it was continuous ly heated at a heating rate of 0.33 K s-1. In the case of MG using the heat-treated powders, an amorphous phase, with a Cr content of about 30 mol.%, was formed at the initial stage of the milling. On further m illing, an amorphous phase of Cr content 20 mol.% was produced. The fo rmer amorphous phase crystallized into the epsilon and delta phases, a nd the latter crystallized into an equilibrium delta phase by subseque nt heat treatment.