| With the development of aerospace technology,it is urgent to further improve the service life of electric contact materials under the precondition of ensuring the reliability of electrical contact signals.The existing precious metal conductive slip ring Au-20Ag-10Cu alloy,as the key contact material of electrical signal transmission system in aerospace equipment,can reach tens of millions of cycles.But it is far from enough to meet the use requirements(over hundreds of millions of cycles).To improve the service life of Au-20Ag-10Cu alloy conductive slip ring is mainly to improve its friction and wear property.For this alloy,hardness is the main index to evaluate its service life.Based on this,this paper systematically studied the effects of solution and aging processes on the microstructure and mechanical properties of Au-20Ag-10Cu.In addition,the alloy machining deformation when can store large amounts of distortion,therefore this article also studied the deformation to the subsequent heat treatment process of ordered phase rule,the influence of precipitation through controlling its microstructure,find out its high hardness and good electrical contact performance of the process,get a"longevity" used in aerospace bar on conductive slip ring.The results of solution treatment show that the recrystallization of 70%Au-20Ag-10Cu alloy occurs at 500-600?,and the recrystallization grains gradually grow up at 600-850?.No second phase was found at different solution temperatures.By increasing the solution temperature of the alloy,it is found that the electrical conductivity and hardness of the alloy show a decreasing trend.The diffraction peaks of the characteristic phases corresponding to the XRD pattern tend to shift to a higher Angle gradually,indicating that the solid solubility of the alloy has been improved.In order to choose the best solution temperature,the solution treatment temperature from 500? to 850? was aged at 300? for 1 hour,and the results showed that Conductivity and hardness of alloys were the best at 850? solution treatment.When Au-20Ag-10Cu alloy was held at 850? for 1 hour and then held at 200-450? for 1 hour respectively,the results of XRD diffraction peak showed that the amplitude-modulated decomposition of Au-20Ag-10Cu alloy occurred after the aging treatment at 350?,and the Au-based solid solutions were decomposed into Ag-rich and Cu-rich solid solutions.AuCu ordered phase appeared at 200,250 and 300?,and the diffraction peak of the ordered phase gradually increased with the increase of temperature.The ordered phase disappeared when the temperature continued to rise.The hardness and electrical conductivity of the samples were tested.It was found that the hardness and electrical conductivity of the alloy were better when the alloy was held at 300? for 1 hour.After solution treatment at 850? for 1 hour,Au-20Ag-10Cu alloy was aged at 300? for different time.The results showed that the hardness and electrical conductivity of the alloy increased to the maximum value at 24 hours and decreased to the maximum value at 48 hours.The main reason is that the ordered transformation of the alloy continues after further prolonging the aging time.According to XRD,the content of AuCu ordered phase increases with the prolonging of aging time,leading to the further improvement of hardness of the alloy.Au-20Ag-10Cu alloy aged at 300? for 1-8 hours mainly underwent matrix a0 phase to AuCu ordered phase transformation.Ag-rich al phase is gradually precipitated from the matrix after 8 h aging.The transition from ?0 phase of matrix to Ag rich al phase and AuCu ordered phase occurs during aging from 8 to 48 hours.After solution treatment at 850? for 1 hour,the alloy was cold-deformed at 10%,30%,50%and 70%respectively,and then aged at 350?for 1 hour.The results show that the hardness of the alloy after solution treatment increases with the increase of deformation,so that the maximum value of 70%is 249.4HV,but the electrical conductivity decreases.The DSC curve shows that the recrystallization temperature of the alloy decreases with the increase of deformation,and the endothermic peak appears at 350?.After aging at 350? for 1 hour,the hardness of the alloy aged after deformation is higher than that of the above isothermal aging,and the hardness and electrical conductivity of the alloy aged after 70%cold deformation are the highest. |
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