The Increase in a Brittle-to-ductile Transition Temperature in Fe–Al Single Crystals

Abstract

The effect of aluminium concentration on a brittle-to-ductile transition (BDT) has been investigated in Fe–Al single crystals. The BDT temperatures in Fe-4mass%Al and Fe-8mass%Al crystals with <100> specimen axis were measured by an instrumental falling weight impact tester, indicating that the BDT temperature in Fe-8%Al is higher than that in Fe-4%Al. Twin-twin intersections were seen on fracture surfaces in Fe-8%Al tested at low temperatures, which shows that the intersection was the origin of a brittle fracture. In order to highlight the effect of deformation twinning on the BDT behaviour, specimens with the <110> axis were also employed to suppress the onset of deformation twinning during the impact tests. The BDT temperature in Fe-8%Al was found to be decreased by suppressing deformation twinning, which indicates that deformation twinning is a key mechanism behind increasing the BDT temperature in Fe–Al single crystals. A model to explain the increase in the BDT temperature with aluminium content is also presented.