Composition Optimization Design Of SiCp/2024Al Based On Phase Stability

At present,the requirements of flight capacity of aircraft are higher and higher in aerospace and other fields,which are closely related to the dimensional stability of precision instruments used in the aircraft.There are many factors that affect the stability of material size,and many people have studied the influence of structure factors and residual stress,but few researches on phase stability.The paper mainly studies the size change of SiCp/2024Al.Firstly,the composition of the matrix alloy was optimized according to the simulation and calculation results.The size change of Cu,Mg content(i.e.cu/mg value)and the temperature aging process were obtained.The matrix alloy with the smallest change in the simulation was found.Then the composite was prepared to observe the size change of the constant temperature material,and the related information of precipitated phase was obtained and analyzed by TEM.The relationship between the element content and the shape of precipitated phase was established.The relationship between the element content control and the size change in the process of constant temperature aging was obtained,and the relationship between lattice constant and the size change of the material during constant temperature aging was established,At the same time,the relationship between the properties of macro materials and microstructure is established.The chemical potential of the three main elements is Cu,Si and Mg from small to large at 190?;The activity was Cu,Mg and Si from small to large.When Cu element is constant,the chemical potential and activity of Cu and Si elements will decrease when mg increases.The Mg element is unchanged.When the Cu element is changed,the increase of Cu element will increase the chemical potential and activity of Si element,but the activity and chemical potential of Mg element will decrease.The content of Cu and Mg also affects the precipitation sequence of precipitates.When Mg content is more than2.3wt%,Cu content increases significantly on the increase of S-phase content,and the Cu content increases at the same time?Phase will increase;Too much mg will decrease?The content of the phase.According to the simulation results,the Mg content in the subsequent alloy design is determined to be 2.4wt%,according to the previous data,Si content is controlled,and Cu content is changed to change the Cu/Mg value to improve the S phase and?Phase content.Through the study of microstructure of five new composite materials,it is found that the change of the size of the composite materials at constant temperature aging is the same as the trend of lattice constant.The change of lattice constant can represent the change of the macro material size.It is found that the larger the content of Cu is,the larger the Cu/Mg value is,the larger the size change of the material is during the constant temperature aging process.When Si content increases to 0.23-0.28wt%.With the increase of cu/mg,the material size tends to decline,and the larger the ratio decreases,the better the size change is Cu 4.3wt%,Mg is 2.4wt%,that is,when cu/mg is 1.8.When the Si content does not increase to 0.1wt%,the size change of the material also shows a downward trend with the increase of cu/mg value.The larger the ratio decreases,the more the size change is,the more optimal the size change is 6.5wt%,Mg is 2.4wt%,that is,when cu/mg is 2.7,the precipitate is a combination of needle and granular s,and the size change can reach 10^-6 grades,which is two orders of magnitude higher than SiCp/2024Al.