Study On Microstructure And Mechanical Properties Of Al-Sc-Zr Alloy Based On Aging And Stirring Friction

Aluminum alloy is the most widely used type of non-ferrous metal structural material in industry which can be widely used in the automotive,aerospace,and wire industries.Adding a small amount of Sc and Zr to pure aluminum can effectively improve the mechanical properties,casting properties and electrical properties of the aluminum alloy.In this thesis,according to a certain proportion of Sc and Zr,Al-0.2Sc-0.04Zr,Al-0.15Sc-0.07Zr,Al-0.1Sc-0.05Zr alloys were prepared by metal mold casting method and tested by hardness test,conductivity measurement,elongation experiment,metallographic observation and scanning electron microscopy in order to study the microstructure evolution and mechanical properties of Al-Sc-Zr alloy during solution treatment,deformation heat treatment and friction stir process.Firstly,the effect of solution aging on the mechanical properties of Al-Sc-Zr alloys was investigated.The Al-Sc-Zr alloy forms a supersaturated solid solution after solution treatment at 600?for 24 hours,and the grain size is suiTab.After Al-Sc-Zr alloy was aged at 300?for 465min,Al₃?Sc,Zr?particles were precipitated and the mechanical properties of the alloy were improved.The hardness and electrical conductivity of Al-0.2Sc-0.04Zr alloy increased to 67.2HV and 60.2%IACS.And the hardness and electrical conductivity of Al-0.15Sc-0.07Zr alloy increased to 55.1HV and 58.9%IACS.The hardness and conductivity of the Al-0.1Sc-0.05Zr alloy increased to 42.3 HV and61.1%IACS.Secondly,in order to investigate the effect of cold rolling on the solid solution aging of Al-Sc-Zr alloys,the solid solution at 600?and the cold rolling deformation of20%,40%,60%,80%and high temperature aging at 300?were carried on.After comparison,it was found that 80%cold rolling deformation has the greatest influence on the mechanical properties of Al-Sc-Zr alloys.The tensile strength,yield strength,elongation and electrical conductivity of Al-0.2Sc-0.04Zr alloy were 235MPa,159.9MPa,6.61%,57.2%IACS.And the tensile strength,yield strength,elongation and electrical conductivity of Al-0.15Sc-0.07Zr alloy were 221MPa,173.9MPa,8.09%,56.7%IACS.The tensile strength,yield strength,elongation and electrical conductivity of Al-0.1Sc-0.05Zr alloy were 212MPa,138.3MPa,8.33%,59.1%IACS.Finally,the effect of friction stir processing on Al-Sc-Zr alloy was explored.By comparing the mechanical properties of ten parameters after friction stir,the suiTab stirring parameter of Al-Sc-Zr alloy was 800rpm×100mm/min.After the friction stir processing,the tensile strength,yield strength and elongation of Al-0.2Sc-0.04Zr alloy were 109.2MPa,46.5MPa and 35.22%respectively.The tensile strength,yield strength and elongation of Al-0.15Sc-0.07Zr alloy were 109MPa,47.4MPa,34.78%.And the tensile strength,yield strength and elongation of Al-0.1Sc-0.05Zr alloy were 104.8MPa,41.2MPa and 34.23%.The above conclusion can provide theoretical support for the performance of rare earth modified aluminum alloy.