Study On The Microstructure And Properties Of 5A12 Aluminum Alloy During Hot Deformation

AI-Mg alloy is a representative non-age-hardenable alloy.Al-Mg alloy is widely used in transportation industry,as an excellent structure material,because of small specific gravity,corrosion resistance and superior welding performance etc.However,the application of Al-Mg alloy is greatly restricted for its relatively low strength.Adding minute amount of rare earth element Sc or Er can improve the strength of Al-Mg alloy.But the price of Sc and Er is too expensive.Using Severe plastic deformation(SPD)technology such as equal channel angular extrusion(ECAE)can prepare fine grain or even super fine grain Al-Mg alloy and obtain comprehensive mechanical property.But these technologies are not suitable for producing large size alloy sheet.So how to obviously improve the mechanical property of AI-Mg alloy by using regular processing means is a subject with great research value.The aim of current study is focused on 5A12 aluminum alloy with high Mg content.Firstly used hot compression stimulation experiment researched hot deformation behavior of this alloy in different Z parameters.Illuminated the dynamic softening mechanism of 5A12 aluminum alloy at hot deformation process in different Z parameters,and provided basis for the formulation of subsequent rolling craft.The influence of deformation condition and initial ingots on the microstructure and properties was researched during multi-pass rolling experiments,and concluded the relationship between microstructural features and mechanical properties of 5A12 aluminum alloy.The main conclusions are obtained:(1)The flow stress and dynamic softening mechanism of 5A12 aluminum alloy were illustrated by hot compression stimulation experiment.The results show:the hot compression deformation process of 5Al2 aluminum alloy is the thermal activation process controlled by dislocation.A hyperbolic sine relationship can satisfactorily correlate strain rate ε and deformation temperature T with flow stress σ by introducing an Arrhenius term as follows:ε =2.25×1014[sinh(0.005σ)]8.22exp(-174600/RT)The dynamic softening behavior is very sensitive to strain rate.At high strain rate and at the low strain rate,these all inhibit the happening of dynamic recrystallization.Increasing the deformation temperature is beneficial for the happening of dynamic recrystallization.At the experimental condition of this study(deformation temperature in 280~400℃,strain rate in 0.1-25s-1),only incompletely dynamic recrystallization structure was obtained in this alloy.(2)The effect of deformation temperature on microstructure and properties of 5A12 aluminum alloy sheets was verified:the yield strength(YS)and ultimate tensile strength(UTS)of the hot-rolled sheets decreased with the rise of the deformation temperature,the elongation(EL)was on the contrary.The best mechanical property of sheet was obtained after rolling at 360℃,the YS,UTS and EL was 446MPa,558MPa and 15%separately.After cold rolling which total elongation was 50%,the mechanical property of the sheet obviously improved,the YS and UTS reached 560MPa and 646MPa separately,and the EL was still 10.5%.(3)The effect of initial ingots on microstructure and properties of 5A12 aluminum alloy sheets was verified:the grain size of the ingots and the amount of non-equilibrium eutectic phase and the degree of supersaturation in the matrix of Zr and Mn increased along with the increased of cooling rate.After homogenization treatment,finer Al3Zr and Al6Mn particles were found.The secondary particles can effectively pin the movement of dislocation and sub-grain.The cold rolled sheets which produced by centrifugal casting ingots exhibited the best mechanical property.The YS and UTS reached 538MPa and 648MPa,and the elongation was 9.7%.