Refinement Of Al-5%Cu And Al-25%Cu Alloys By Means Of Kobo Methods

This study was undertaken to investigate the effect of severe plastic deformation (SPD) by extrusion combined with reversible torsion (KoBo) method on microstructure and mechanical properties of Al-5Cu and Al-25Cu alloys. The extrusion combined with reversible torsion was carried out using reduction coefficient of lambda = 30 and lambda = 98. In this work, the microstructure was characterized by light microscopy (LM), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). Compression test and tensile test were performed for deformed alloys. The binary Al-5Cu and Al-25Cu alloys consist of the face cantered cubic (FCC) alpha phase in the form of dendrites and tetragonal (C16) theta-Al2Cu intermetallic phase observed in interdentritic regions. The increase of Cu content leads to increase of interdentritic regions. The microstructure of the alloys is refined after applying KoB deformation with lambda = 30 and lambda = 98. Ultimate Tensile Strength (UTS) of Al-5Cu alloy after KoBo deformation with lambda = 30 and lambda = 98 reached about 200 MPa. UTS for samples of Al-25Cu with lambda = 30 and lambda = 98 increased compared to Al-5Cu alloy and exceed 320 MPa and 270 MPa respectively. All samples showed increase of plasticity with increase of reduction coefficient. Independently of reduction coefficient, the compressive strain of Al-5Cu alloys is about 60%. The Al-25Cu alloy with lambda = 98 showed the value of compressive strain exceed 60%, although for this same alloy but with lambda = 30, the compressive strain is only 35%.