Severe Plastic Deformation Induced Precipitation Melting On The Microstructure And Properties Of Al-Cu Alloy Phase Back

The re-dissolution of second phase particles during severe plastic deformation(SPD) is a new significant micro-phenomenon.In order to investigate the effect of the re-dissolution of second phase particles on the structures and properties of Al alloy,the experimental materials as Al-Cu were employed in this paper.The mechanical properties were measured by means of hardness measurement and tensile test at room temperature and the evolution of microstructures was characterized by optical microscopy,scanning electron microscopy,transmission electron microscopy and x-ray diffraction analysis.The main results are as follows:The strength has an increase in all the four conditioned specimens (solution treated,containingθ″,containingθ′,containingθ) during multi-axial compression,the ductility of the sample containingθ″and the sample containingθ′were improved while the ductility of the solution treated sample and the sample containingθdecreased with the strain increasing.The precipitated phases were re-dissolved during multi-axial compression in the sample containingθ″and the sample containingθ′, which caused the decrement of precipitated phases strengthening,so the increase extent of strength is not so large as that of the solution treated sample and the sample containingθ,the ductility of SPD materials can be improved by the re-dissolution of precipitated phases.Supersaturated solid solution is formed by re-dissolution of precipitated phases during multi-axial compression in the sample containingθ″and the sample containingθ′,during subsequent annealing, new precipitated phases will precipitate again from the strain-induced solid solution,which can strength the matrix,and the precipitated rate is significantly accelerated.The precipitated rate is related to heating temperature and the total strain.When annealing at 120℃,the strength of the sample containingθ″and the sample containingθ′will be increased,while the strength of the sample containingθdecreased because of the recovery of work hardening.The samples containingθ″ and the sample containingθ′have little change in strength when annealing at 150℃,while the sample containingθhas an obvious decreasing tendency in strength.When annealing at 200℃,the strength of all the three conditioned specimens have an obvious decreasing tendency.The annealing hardening at 120℃is due to combined effect of re-precipitate strengthening and the recovery of strain hardening.When the precipitated phases are not re-precipitated completely during multi-axial compression,the precipitated phases re-dissolve and re-precipitate alternately during subsequent annealing and the strength of annealing sample is lower.The strain extent has a significant effect on the annealing properties of Al-Cu alloy,and the samples that the precipitated phases were re-dissolved completely exhibit best overall qualities after subsequent annealing.