Effect of Cold Work and Trace Rare-Earth Additions on the Aging Behavior of Al–Cr Alloys Containing Zirconium

Precipitation behavior during aging of a cold-worked aluminium chromium alloy containing zirconium has been investigated by electron microscopy transmission. The effect of trace rare-earth additions on the aging behavior of Al–Cr–Zr alloys has been studied using microhardeness testing and metallographic analysis. A detailed microstructural analysis revealed that the age hardening in these alloys is mainly due to the formation of precipitates on dislocations. It was further noted that cold working prior to aging greatly accelerated the process of age hardening, and a two-stage hardening has been observed in most of the alloys with or without cold work. Two types of precipitates, viz CrAl7 and Cr2A11, formed at different aging temperatures, have been identified.