Analyses of Aging in Aluminum Cast Alloys by X-Ray Diffraction

Aluminum alloys are used due to their combination of weight and strength, which is obtained by heat treating. The alloying elements are put in solution at a high temperature, and cooling at a rate fast enough for them to remain in solution; strengthening is produced by precipitation. This work presents the results of analyses on cast aluminum alloys hardened by either the precipitation of Mg₂Si or Al₂Cu. The samples were solution treated at temperatures adequate for the different alloys and cooled by placing them in hot water. Aging was conducted at two different temperatures in all cases for times as long as 200 hrs. Changes due to aging were documented by microhardeness, microscopical examination and by X-ray diffraction. X-ray examination showed that the peak corresponding to the {311} position shifts the aging condition, indicating changes in the lattice parameter of aluminium, which depends on the type of particle that precipitates.