Effect of the Processing Conditions on the Microstructural Features and Mechanical Behavior of Aluminum Alloys

Aluminum and aluminum alloys are widely used for aircraft structures, where they are subjected to demanding conditions and where is an increased demand for weight reduction and fuel savings. Aluminum comprises 8% of the earth?s crust and is, therefore, the most abundant structural metal. Its production since 1965 has surpassed that of copper and now comes next to iron. This increased use of aluminum alloys leads to a need for deeper understanding of their mechanical properties and the impacts of processing parameters. The mechanical properties can determine by controlling the microstructures of the alloys. For example, precipitation hardening is the main strengthening mechanism improving the tensile and yield strength. Solute atoms, precipitates and dispersoids influences to the yield strength, since they act as distributed pinning points for mobile dislocations, thus increasing the shear stress required to move the dislocations. Another approach is the manipulation of a grain size that can be performed by alloying or plastic deformation processes. Therefore, the precise understanding of each mechanism that can influence the properties of aluminum and its alloys is very important. The aim of this chapter is to shed light on the influence of the processing history on the microstructure and mechanical properties

HPDL Remelting of Anodised Al-Si-Cu Cast Alloys Surfaces

The results of the investigations of the laser remelting of the AlSi9Cu4 cast aluminium alloy with the anodised and non-anodised surfacelayer and hardness changes have been presented in this paper. The surface layer of the tested aluminium samples was remelted with thelaser of a continuous work. The power density was from 8,17•103 W/cm2 to 1,63•104 W/cm2. The metallographic tests were conducted inform of light microscope investigations of the received surface layer. The main goal of the investigation was to find the relation betweenthe laser beam power and its power density falling on a material, evaluating the shape and geometry of the remelted layers and theirhardness. As the substrate material two types of surfaces of the casted AlSi9Cu4 alloy were applied – the non–treated as cast surface aswell the anodized surface. As a device for this type of surface laser treatment the High Power Diode Laser was applied with a maximumpower of 2.2 kW and the dimensions of the laser beam focus of 1.8 x 6.8 mm. By mind of such treatment it is also possible to increasehardness as well eliminate porosity and develop metallurgical bonding at the coating-substrate interface. Suitable operating conditions forHPDL laser treatment were finally determined, ranging from 1.0 to 2.0 kW. Under such conditions, taking into account the absorptionvalue, the effects of laser remelting on the surface shape and roughness were studied. The results show that surface roughness is reducedwith increasing laser power by the remelting process only for the non-anodised samples, and high porosity can be found in the with highpower remelted areas. The laser influence increases with the heat input of the laser processing as well with the anodisation of the surface,because of the absorption enhancement ensured through the obtained alumina layer