Study On Microstructure,properties And Hot Working Diagram Of Sc,Zr Composite 5083 Aluminum Alloy

The main alloying element of 5XXX series aluminum alloy is Mg,which has low alloy density,high tensile strength and good corrosion resistance.It is widely used in automobile,ship and other fields.With the development of national economy,higher requirements for material properties are put forward.Increasing Mg content can improve the strength,but it will reduce the corrosion resistance,lead to the limit the of Mg addition.In view of the contradiction between the strength and corrosion resistance of 5XXX aluminum alloy,5083 aluminum alloy was studied in this paper.The effects of 0～0.4wt.%Sc,Zr and compound addition of Sc and Zr on the microstructure and properties of as-cast and homogenized annealed alloys was studied by means of optical microscope,X-ray diffraction,scanning electron microscope,differential thermal analysis,Brinell hardness,tensile test and intergranular corrosion,so as to optimize the addition amount,improve the properties and control the cost.In addition,Gleeble3500 thermal simulation was used to study the changes of the constitutive equation of the alloy after the compound addition of Sc and Zr.The main conclusions are as follows:（1）After adding 0.2wt.%Sc+0.1wt.%Zr,the main phases of the alloy remain unchanged,most of Sc and Zr are dissolved in the matrix,the coarse dendrite changes into fine dendrite and equiaxed dendrite,and the grain size decreases.The reticulative Al₃Mg₂ and Al₆（Mn,Fe）distributing at the grain boundary are refined,which transformed into granular and fine strip.（2）Within the scope of research,Sc and Zr can effectively improve the mechanical properties of the alloy.Adding 0.2wt.%Sc,the tensile strength of as-cast alloy increased from 158.6Mpa to 217.0Mpa,an increase of 37%.Adding0.15wt.%Zr increases the strength to 184.4Mpa,an increase of 16%,and 0.1wt.%Sc+0.03wt.%Zr increases to 199.5Mpa,with an increase of 25.7%.The hardness is slightly improved.The compound addition effect of Sc and Zr is greater than that of single addition,which is conducive to reducing the cost.（3）After 470℃×After 24h homogenization annealing,coarse Al₃Mg₂redissolved or formed into granules.The tensile strength of 5083 aluminum alloy increased to 192.4MPa,the strength of alloy containing 0.2wt.%Sc increased to260.1Mpa,and the strength of alloy containing 0.1wt.%Sc+0.03wt.%Zr increased to 253.9MPa,and the elongation improved,indicating that adding a few of Sc and Zr can effectively refine the second phase Al₃Mg₂ as anode,passivate and spheroidize Al₃Mg₂,improve the homogenization effect of the alloy,and further improve the mechanical properties and corrosion resistance of the alloy.（4）Considering the performance and economic factors,the thermal deformation behavior of the alloy with 0.1wt.%Sc+0.03wt.%Zr was studied by Gleeble3500 thermal simulation machine.The results show that the thermal activation energy Q of 5083 aluminum alloy at 30%,50%and 70%deformation is 180.9,175.8 and 144.1k J/mol respectively.After alloying,Q is 161.8,163.8and 163.6 k J/mol respectively.At 30%and 50%deformation,the thermal deformation activation energy of the alloy is reduced by about 19.2 and12.0k J/mol respectively.Alloying is conducive to the deformation of the alloy;At70%deformation,the Q value of alloying is about 19.5k J/mol higher than that of5083 aluminum alloy,which can pin dislocations and inhibiting recrystallization more effectively.