Preparation, Microstructure And Properties Of High Strength And Toughness Al-Cu Alloys

Al-Cu is a typical aluminum alloy of high strength and high toughness,which has been widely used in aerospace and automotive manufacturing field due to its good comprehensive properties,such as high strength,good ductility and plasticity.At present,Al-Cu alloy has been unable to meet the application requirements along with the improvement of aluminum alloy new model indicators,so the development of new high strength and high toughness aluminum alloy is particularly important.In this paper,the effects of various alloying elements on the microstructure and mechanical properties of aluminum alloy have been analyzed,the chemical composition range of Al-Cu alloys have been designed firstly,and then the designed Al-Cu alloys have been melted,refined,degassed and casted.By Optical Metallographic Microscope?OM?,X-ray Diffraction?XRD?,Scanning Electron Microscope?SEM?,Rockwell Hardness Tester,and analysis of test equipment,such as universal testing machine,the effects of the Al5Ti1B addition amount on microstructure and mechanical properties of Al-Cu alloy have been studied,and the suitable content of Al5Ti1B has been determined.Then the effects of solid solution and aging treatment process on the microstructure and mechanical properties of Al-Cu alloy with the optimal Al5Ti1B content have been investigated,and the optimal heat treatment process has been determined.The research results showed that the contact microstructure of Al-Cu alloy could be obtained after 3 times of refining and rotating injection for 20min degassing.The cast microstructure of Al-Cu alloy is mainly composed of??Al?,??Al₂Cu?and Al₃T phases.Grain refinement effect of A15Ti1B is distinct,but refinement limit phenomenon exists.For Al-5Cu and Al-6Cu,when A15Ti1B addition amount was less than 0.6wt.%,grain size reduced with the inctreasing of the A15TiB content,but the grain size increased when A15Ti1B content was more than 0.6wt.%.The addition amount A15Ti1B of 0.6wt.%is best,and the average grain size is about 40?m and 30?m,respectively.For Al-5.5Cu alloy,the average grain size is about50?m with the optimal addition amount of 0.4wt.%A15Ti1B.The solid solution and aging treatment of the three kinds of Al-Cu alloy with optimal Al5Ti1B addition has been studied.The results showed with the increasing of solution temperature and extending of holding time,the amount of dissolved phase decreased and the grain size had increasing trend,gradually;With the increasing of aging temperature and aging time,the amount of precipitated phase which had the trend of gathered growing up increased,.The optimized solid solution and aging treatment process of three kinds of Al-Cu alloys are as follows:Al-5Cu alloy,535?/15h solid solution,and 175?/12h aging treatment;Al-5.5Cu alloy and Al-5cu alloy,535?/15h solid solution,and 175?/15h aging treatment.The tensile properties of the three kinds of Al-Cu alloy with optimal Al5Ti1B alloy addition amount has been tested after solid solution and aging treatment.The results showed that highest tensile properties for Al-6Cu alloy with A15Ti1B addition amount of 0.6wt.%by535?/15h solid solution and 175?/15h aging treatment could be obtained.The tensile strength of this alloy is 491 MPa,and the elongation 12.7%.