Study On The Precipitation Behavior Of Ordered Phase And Hardening Mechanism Of Au-20Ag-10Cu Alloy During Solution-Deformation-Ageing Treatment

Au-20Ag-10Cu alloy is widely used as electrical contact materials for aerospace equipment because of its excellent electrical and thermal conductivity,oxidation resistance,low contact resistance and stability.The friction and wear damage of electrical contact materials is one of the main problems which lead to the instability of electrical signal and affect the service life of electrical contact materials.To ensure the reliability of electrical contact signals,it is imperative to further improve the hardness of the alloy to extend its service life.The "solution-deformationaging" treatment can realize the control of microstructure and properties by adjusting the process parameters,which is the key treatment process for Au-20Ag-10Cu alloy to obtain excellent performance.In this paper,in order to explore the optimal treatment process,the microstructural changes and phase transformation behavior of Au-20Ag-10Cu alloy subjected to the "solutiondeformation-aging" process were investigated,by means of DSC,XRD,OM,SEM,TEM,EBSD characterization techniques,microhardness and conductivity tests.The main findings and conclusions are as follows:(1)Au-20Ag-10Cu alloy has different types of precipitated phases at different aging temperatures,the ability to improve the properties of the alloy is different.At 235℃,The solute atoms were segregated to form metastable silver-rich α1’ phase.While equilibrium AuCu I ordered phase was precipitated at 300℃.By comparing the properties of deformation of 70%alloy aged for 16h at two different temperatures,it was found that the improvement of the ordered relative properties of the equilibrium AuCu I was better than that of the metastable silver-rich α1’phase.(2)The deformation,aging temperature and time have great influence on the distribution,content and size of the precipitated phases of the alloy.A higher deformation,higher aging temperature and longer aging time can effectively improve the trend of AuCu I ordered phase dispersion distribution during aging process.The increase of deformation can decrease the size of the ordered phase and increase the content.The size of ordered phase could be increased with the extension of aging time.AuCu I ordered phase has a {100}α0//{100}AuCuI coherent relationship with the matrix.(3)The deformation,aging temperature and time have great influence on the microhardness and conductivity of the alloy.After deformation and aging treatment,the microhardness increases and the conductivity decreases of the alloy with the increase of deformation.With the increase of aging time,the microhardness increases and then fluctuates,and the conductivity increases gradually.After 70%deformation treatment and aging at 300℃ for 16 h,the microhardness and conductivity of 307.44 HV and 8.40 MS·m-1,respectively,and the optimum preparation process of Au-20Ag-10Cu alloy was obtained.(4)The improvement of microhardness of alloy after "solution-deformation-aging"treatment mainly comes from ordered phase strengthening and dislocation strengthening.With the increase of aging time,the ordered phase content increases,the content of LAGB increases,and the dislocation density decreases to some extent,but the strain distribution in the organization becomes more uniform.The above factors affect the properties of the alloy,improve the microhardness and conductivity of the alloy.