Influence of aluminium on carbide precipitation in low carbon microalloyed steels

Abstract

Precipitation in an 0·1C–0·5Si–1·5Mn–0·15Mo–0·5Ni–0·05V–Fe(wt-%) alloy containing from 0·04 to 0·2 wt-%Al was examined in the tempered condition. After hot rolling, the steels were solution treated at 1200°C for 2 h, then quenched in water. Tempering was mainly carried out at 600 or 650°C for 1 h. The precipitates were identified and measured using transmission electron microscopy and energy dispersive X-ray analysis. It was found that coarsening of Fe₃C carbides in the prior austenite grain boundaries was associated with low Al content, while the size of Fe₃C particles in the lath boundaries was independent of Al content. It is proposed that Al segregated to the prior austenite grain boundaries during solution treatment, associated with vacancies, and decreased the rate of vacancy migration, thereby retarding the coarsening of cementite.

MST/1707