ENHANCED MECHANICAL-PROPERTIES OF LASER TREATED AL-CU ALLOYS - A MICROSTRUCTURAL ANALYSIS

Both mechanical Vickers hardness and electron microscopic studies have been carried out on laser treated aluminium copper alloys with a copp er concentration in the range 0-40 wt%. It is found that a Vickers har dness of 470 kgf/mm(2) can be attained, which is high compared to a va lue of 120 kgf/mm(2) for conventionally heat treated Dural. The micros tructure, which causes this difference in hardness, is analysed by tra nsmission electron microscopy. The findings are: Al2Cu strong localize d obstacles, Al-Al2Cu interfacial energy, cellular to lamellar transit ion, misfit dislocations, perfect glissile dislocation loops and a vac ancy supersaturation. All these features effect hardness in their own way. Based on a composite model of the microstructure the hardness vs laser scan velocity could be predicted in fair agreement with experime nts.