Investigation Of Diffusion Behavior And Mechanical Properties Of Cu-Zn And Mg-Zn Systems

As the most common alloy materials,Al-Zn-Mg-Cu series alloy has been widely aplied in aerospace,military,automotive,electronics industry and medical fields because of its a series of advantages such as high specific strength,good corrosion resistance,low density and low cost.It taken as defence-related science and technology and the key supporting technology.Therefore,it has attracted a great of attendance.It is of great significance to further study the diffusion behavior,microstructure and the mechanical properties of intermetallic compounds?IMCs?.In this paper,the diffusion processes of Cu-Zn and Mg-Zn binary systems have been investigated by electron probe microanalysis?EPMA?and nanoindentation.Growth constants,diffusion coefficients and mechanical properties of the two binary systems have been evaluated.This main conclusions are as follows:?1?The Cu-Zn binary diffusion couple was annealed at a temperature ranging from 290? to 380?.Three intermetallic compounds ?',? and ? have been observed.They have been determined to be CuZn,Cu₅Zn₈ and CuZn5 by the analysis of EPMA.The growth of intermetallic compounds follows the law of parabolic growth.?2?The interdiffusion coefficient and diffusion activation energy of each phase have been estimated.At each temperature,the order of the magnitude of interdiffusion coefficient of intermetallics is of DCu₅Zn₈>DcuZn5>DcuZn.The diffusion activation energies of CuZn,Cu₅Zn₈ and CuZn5 phases are 106.25,97.95 and 112.01 kJ/mol,respectively.?3?The hardness of CuZn,Cu₅Zn₈ and CuZn5 have been measured and they are 1.67 GPa,6.81 GPa and 2.74 GPa,respectively.The Young's modulus are 105.71 GPa,186.76 GPa and 137.77 GPa,respectively.The smaller the creep stress index of the intermediate compound,the stronger the creep resistance.The creep stress index of CuZn5 with the lowes index and then it has the strongest creep resistance.?4?For Mg-Zn binary system,the annealing temperature is from 250? to 320?.There are four intermetallic compounds Mg21Zn25,Mg₂Zn₁₁,Mg4Zn7 and MgZn2 have been observed.The growth constant,growth activation energy,interdiffusion coefficient,and diffusion activation energy of the intermetallic compounds have been obtained.The MgZn2 phase has the largest diffusion coefficient and the smallest activation energy,which is 34.76kJ/mol.The diffusion coefficient of Mg21Zn25 phase is the smallest and the diffusion activation energy is up to 88.89kJ/mol.?5?The hardness of Mg₄Zn₇ is 5.45GPa,and the modulus of Mg₂Zn₁₁ is 132.87GPa.The minimum creep stress index of Mg₂Zn₁₁ is 0.71,then followed by MgZn2 and Mg21Zn25,Mg4Zn7.It is shown that Mg₂Zn₁₁ has the strongest creep resistance among the four intermetallic compounds.