LAUSR

The objective of this work was to investigate the effect of rapid heating and cryogenic cooling on the fracture and tensile properties of Al-Cu-Mg samples. The specimens were subjected to three different heat treatment cycles in which the Infrared heating (IR) were used as the heating medium at the ageing stage, and the liquid nitrogen and water were used as the quenching mediums. The ageing temperature and time were 1900C and from 2 to 10h respectively. The results indicated that by using IR at the ageing stage, the hardening rate enhanced because the rapid heating via this method led to faster diffusion of the alloying elements. Moreover, the high density of nanosized precipitates formed during ageing was another reason for higher strength and ductility. Cryogenic treatment had a negligible effect on both the microstructure and tensile properties. However there was an improvemnet in the ductility to some extent. Overall, the combination of a high heating rate and cryogenic treatment led to the highest mechanical properties. SEM micrographs of the fracture surface demonstrated that in Cryogenic treatment plus Artificial Ageing (CAA) condition, the surface was fully covered by deep dimples in contrast to the Cryogenic treatment plus Infrared Heating (CIR) and Water-Quench plus Infrared Heating (QIR) conditions which contained shallwer dimples. Some facets were also observed in the latter samples.