Effect Of Zirconium And Vanadium On Microstructures And Mechanical Properties Of Squeeze Cast Al-5.0Cu-0.4Mn Alloys

The Al-Cu-based casting alloys have been widely used in the fields of transportation,machinery,aviation and many other fields owing to their high strength and good toughness.Much concern focuses on the improvement of the comprehensive performance of the alloys.Squeeze casting,as an advanced near-net-shape forming technology to realize compact structure and eliminate the casting defects,can not only produce complex parts,but also obtain high surface quality of the castings,and is one of the effective ways to obtain high strengthen and toughness aluminum casting alloy.In addition,micro-alloying has been also utilized to improve the mechanical properties of the aluminum alloys.In this work,the squeeze casting technology and micro-alloying were combined to prepair the Al-5.0Cu-0.4Mn alloy.The effect of the trace elements Zr and V on the microstructures and mechanical properties of the Al-5.0Cu-0.4Mn alloys with or without Ti and RE were studied by tensile test,macro corrosion,optical microscope?OM?,scanning electron microscope?SEM?,Energy dispersive spectrum analysis?EDS?and transmission electron microscope?TEM?.Then compared with the corresponding gravity cast alloys,the optimal alloy composition with the best comprehensive performance was obtained,and the trial manufacture of heavy load wheel was carried out based on the optimal alloy composition.The main conclusions are as follows:?1?As for the as-cast Al-5.0Cu-0.4Mn alloys prepared by squeeze casting and gravity casting,the ultimate tensile strength,yield strength and elongation reach their peak values at 0.25%Zr content.As for the heat-treated alloys,the ultimate tensile strength and yield strength increase obviously with the increase of Zr content from 0% to 0.25%,while the maximum elongation appears at 0.15%Zr.Squeeze casting can significantly improve the elongation,and the elongation of the as-cast alloy is definitely superior than that of the heat-treated alloy.As for the as-cast Al-5.0Cu-0.4Mn alloy with or without Ti and RE addition,the main strengthing mechanism of the Zr is grain refinement strengthening.However,after T6 heat treatment,solid solution strengthening and dispersion strengthening of the Al₃Zr particle and ?'?Al₂Cu?phase are the main strengthing mechanisms.Squeeze casting can significantly improve the dispersion strengthening effect of the Al₃Zr particles.The effect of Zr on the precipitation of ?' and T(Al₂₀Cu₂Mn₃)phases is not obvious.The applied pressure can promote the precipitation of ?' phase,while retard the precipitation of T phase.?2?As for the as-cast Al-5.0Cu-0.4Mn alloy prepared by squeeze casting and gravity casting,the ultimate tensile strength and yield strength show a parabolic change with the increase of V content,and the peak values obtain at 0.25%V content.While the elongation changes little when the V content is less than 0.25%,but falls dramatically when the V content exceeds 0.25%.As for the heat-treated Al-5.0Cu-0.4Mn alloy,the maximum ultimate tensile strength,yield strength and elongation appear at V content of 0.25%.The refinement in the as-cast Al-5.0Cu-0.4Mn alloy by V addition is not as good as Zr.After T6 heat treatment,V can accelerate the precipitation of ?' phase,while retard precipitation of T phase when the content of V exceeds 0.25%.V is mainly dissolved in the a?Al?matrix and T phase.The excess V forms the primary coarse Al₁₀V,and its morphology and composition do not significantly change after heat treatment.?3?As for the Al-5.0Cu-0.4Mn alloy containg 0.1%Ti and 0.1%RE,after T6 heat treatment,the optimal comprehensive performance appears at Zr content of 0.15% for both squeeze casting andgravity casting.And the maximum ultimate tensile strength,yield strength and elongation appear at V content of 0.25%.When Zr and V are added simultaneously,the optimal comprehensive performance appears at Zr content of 0.05% and V content of 0.15%.The optimal ultimate tensile strength is 462 MPa,yield strength is 365 MPa and elongation is 18.6% when the squeeze pressure is 100 MPa.The “Zr poisoning” effect emerges when the Zr content increased to 0.15%.The primary coarse Al₁₀V appears at V content of 0.05%,and the number and size increase with the increase of V content.Squeeze casting is difficult to eliminate the “Zr poisoning” phenomenon and has no obvious effect on the number and morphology of Al₁₀V phase containg Ti and RE.?4?The squeeze casting of heavy load wheel is developed based on Al-5.0Cu-0.4Mn-0.1Ti-0.1RE-0.05Zr-0.15 V alloy.The wheel is obtained by squeeze casting using multi stage filling on the basis of numerical simulation.After T6 heat treatment,the mechanical property of the wheel is much better than those of the conventional A356 alloy wheels.