The Effects Of Heat Treatment And Deformation On The Microstructure And Properties Of Al-Cu-Mg-Sc-Zr Alloy

Al-Cu-Mg alloys have been widely used for structural materials in the automobile,aerospace and other industrial fields due to high strength,fatigue resistance and excellent performance of processing.And rare earth element Sc has been considered to be the most efficient micro-alloying element in the aluminium alloy,the advantages of which in grain refinement,recrystallization resistance and dispersion strengthening attract much attention.However,the high cost of Sc limited its wide application in the aluminum alloy,so the introduction of other modifying elements is of great necessity to reduce the cost.In this paper a new type of aluminum alloy material with Sc and Zr addition is studied.Furthermore,it is important to optimize the heat treatment and deformation process to improve the comprehensive performance,which has theoretical significance and application value on the research of light-weight and high-strength aluminum alloy.In this work,two kinds of Al-Cu-Mg-Sc-Zr alloys with different compositions were designed.The effects on Al-Cu-Mg alloys' microstructure and properties with Sc and Zr addition were studied.Furthermore,the effects of deformation process and heat treatment on the microstructure and properties were also investigated.The main conclusions are listed as follows:Sc and Zr additives in the alloys improve the cast structure due to primary Al3(Sc,Zr)precipitates,the precipitates of bean-like secondary Al3(Sc,Zr)particles further strengthen the alloy via pinning the dislocations which are formed during pre-deformation and hindering the dislocation motion.In addtion,the recrystallization temperature of the alloy is improved.The tensile and yield strength gradually increase,but the plasticity decreases with the increase of pre-deformation amount,and the dual-peak aging phenomenon is eliminated due to the overlap of the segregation area and the metastable phase with the introduction of pre-deformation.Furthermore,the pre-aging process before pre-deformation enhances the plasticity in a certain extent on the basis of assuring the alloys' strength.The study on the Al-Cu-Mg-Sc-Zr alloy of high Mg content shows that the synergism of pre-deformation(20%)and pre-aging(130?/1h)achieves better mechanical properties: tensile strength is 488 MPa,yield strength is 391 MPa and the elongation is 11.2%.The tensile and yield strength respectively increase by 15.9%and 15.7% than conventional solution and artificial aging(T6)process.Meanwhile the pre-deformation process promotes the kinetics of aging and decreases the peakaging time.And the experiment of the Al-Cu-Mg-Sc-Zr alloy of low Mg content indicates that both low temperature and high temperature pre-aging process can achieve better mechanical properties.The tensile strength and yield strength with130?/1.5h pre-aging are 473 MPa and 375 MPa,while the elongation is 12.3%.And the tensile strength and yield strength with 280?/15 min pre-aging are 470 MPa and383MPa,while the elongation is 12.0% respectively.