Mechanical properties and microstructure of an Al-4%Cu alloy severely deformed by equal channel angular pressing

Abstract

Equal channel angular pressing (ECAP) is the name given to a deformation process able to produce very fine grain size in metallic alloys. Its central characteristic is the ability to produce severe plastic deformation, thus providing a very high thermodynamic potential for processes such as recovery and recrystallization. Deformation levels are very high, reaching 10 or more, and can be obtained under relatively low mechanical loads and in conventional presses. The recent literature shows that ECAP hyper-deformation is applicable to a wide variety of alloys, viz: Cu, steels, Mg and Ti alloys, and above all to Al alloys. Current research is directed to process features: die/sample friction, die geometry, processing routes, deformation temperature, post-deformation heat treatments and microstructural changes due to the deformation. The motivations, objectives and results of these studies deal with fundamental aspects of plastic deformation, ultra-fine grains formation mechanisms and how to reach high levels of mechanical strength and ductility. More recently, techniques to obtain large sections of hyper-deformed materials are being developed, as well as near net shape products. One of the most interesting outcomes of the ECA process is superplasticity, a property which is required for the hydroforming of Al tubes and profiles for the automotive industry. This project seeks the application of ECA-deformation to an Al-4%Cu alloy, in order to obtain sub-micrometer grain size, plus the analysis of the effects of this microstructural feature in terms of mechanical strength, including the effects of pre- and post-deformation heat treatments. A minimum of four ECA passes will be applied at room temperature, to an extruded, homogenized and slow cooled Al-4%Cu alloy. Characterization includes hardness measurements, tensile tests, transmission electron microscope and EBSD observations. At the same time, the ECA die design will be improved. (AU)