Study On Diffusion And Diffusion Layer Structure And Mechanical Properties Of (AlZn)-X(X=Al,Mg,Cu)

As one of the most important alloy materials,Al-Zn-Mg-Cu series alloy has a lot of advantages,such as high specific strength,good processability,low density and good fatigue resistance,at present,which has been widely used in aerospace,shipbuilding,construction and other fields.The stability of the internal microstructure of the material has a great influence on the properties and application of aluminum alloy,therefore,it is of great significance to deeply study the diffusion behavior between the alloy elements and the mechanical properties of the formed intermetallic compounds.In this paper,the diffusion properties and mechanical properties of?AlZn?-Al,?AlZn?-Mg and?AlZn?-Cu have been investigated by electron probe microanalysis and nanoindentation.The conclusions are as follows:?1?Three kinds of alloys with different Zn contents of Al-5at.%Zn,Al-9at.%Zn and Al-12at.%Zn were prepared by smelting.In this paper,?AlZn?-Al diffusion couple composed of Pure Aluminum and solid solution and the impurity diffusion coefficient of Zn in each sample at 773K was calculated,the order of diffusion coefficient is D _{Al-?Al-12at.%Zn?}>D _{Al-?Al-9at.%?Zn}>D Al-?Al-5at.%Zn?.?2?The mechanical properties of solid solution region of Al-Zn system were analyzed by nanoindentation.The results show that:When the content of Zn is 9.81at.%,the hardness of the solid solution region of Al-Zn system is 2.41?±0.1?GPa.?3?Three kinds of diffusion couples with different Zn contents?Al-3at.%Zn?-Mg,?Al-4.5at.%Zn?-Mg and?Al-9at.%Zn?-Mg were melted and produced,annealed at 673K,and determination of components by EPMA.The results shows that:There are three intermetallic phases of Al₃Mg₂,Al₆Mg₁₁Zn₁₁ and Al₁₂Mg₁₇ in all diffusion couples,in addition,there is a intermetallic phase of Al₅₅Mg₄₅ in the?Al-9at.%Zn?-Mg diffusion couple.The growth constants of the above intermetallic compounds were calculated,and the growth constant of Al₃Mg₂ is the largest,the interdiffusion coefficients of Al₃Mg₂ and Al₁₂Mg₁₇ compounds under different conditions were estimated.?4?For?AlZn?-Mg system,When the content of Zn is 3at.%,the hardness of Al₃Mg₂ is the highest,and the hardness is 6.615?±0.2?GPa.The hardness of Al₁₂Mg₁₇ phase is similar to that of 5.272?±0.2?GPa when the content of Zn 4.5 at.%.?5?Three kinds of diffusion couples with different Zn contents?Al-0.32at.%Zn?-Cu,?Al-3.2at.%Zn?-Cu and?Al-4.5at.%Zn?-Cu were melted prepared,and annealed at 773K.There are two intermetallic phases of Al₂Cu,Al₄Cu₉ in all diffusion couples.The growth constants of the above intermetallic compounds were calculated,the growth constant of Al₄Cu₉ is the largest,the interdiffusion coefficients of Al₂Cu and Al₄Cu₉ compounds under different conditions were estimated.?6?For?AlZn?-Cu system,when the content of Zn is 3.2 at.%,the hardness of Al₂Cu and Al₄Cu₉ compounds reach the maximum,the hardness of Al₂Cu phase is 6.341?±0.5?GPa;and the hardness of Al₄Cu₉phase is 8.246?±0.5?GPa.