An Efficient Test Method For Material Properties And Technological Parameters And Its Application In 7055 Aluminum Alloys

In the material heat treatment process parameters,the temperature,holding time and cooling rate is the most important three parameters,in which the cooling rate is the most difficult to quantify the amount.This paper explores a method of measuring cooling rate of quenching in order to obtain good microstructure and mechanical properties by means of a low test and efficient quantification method.The relationship between the temperature field of the cooling process and the organization and properties of the material is established.First,the end quench test and simulation of the temperature field are combined with each other to obtain an accurate spatial continuous temperature field,and then the micro-specimen characteristics of the small punch test are used to ensure that the measured mechanical performance can reflect the specific cooling rate.Correspondence between the cooling rate,microstructure and performance are also ensured by the metallographic phase and hardness test in the same section.In this paper,spray forming 7055 aluminum alloy is used as the experimental material to study the effects of different quenching cooling rates on its microstructures and performance under two-stage solid solution at 450?for 3 hours and 475?for 3hours and two-stage aging treatment at 115?for 8 hours and 155?for 36hours.The research results are as follows:Through the end quench test and simulation of the temperature field are combined with each other to obtain an accurate spatial continuous temperature field,so that the correspondence between cooling rate and performance can be achieved in different cross-section.The SPT results of materials from end quench test show that the values of yield load and maximum load of the material are the highest at 6mm from the end of the quenching surface,which means that the material has the best mechanical properties at this cooling rate.The microstructure in this zone is the large second phase distribute dispersively in the grains,the grain size is 11,the hardness is 184.74HV.With the reduction of the quenching cooling rate,the second phase precipitates,and the solid solution supersaturation of the material after quenching is reduced.Strenthening phase??MgZn₂?is precipitated after age,the second phase is the common composition of precipitation during solid solution cooling and aging precipitation,and the grain size of precipitation of solid solution is relatively coarse.The microhardness increased significantly after aging,which is the result of aging hardening;with the reduction of quenching cooling rate,the microhardness decreases gradually;the change trend of quenching sensitivity and electrical conductivity are the same as cooling rate changes,both of which gradually increase as the cooling rate decreases.