Influence Of Deformation Temperature And Deformation Times On Microstructure And Properties Of 7A04 Aluminum Alloy

With the increasing demand of energy conservation and environmental protection,people are paying more attention to the weight reduction of transportation Vehicles.Aluminum alloys are the most preferred light-weigh material for its high strength,high ductility,high welding capacity and corrosion resistance.Among of them,as heat-treatable high strength aluminum alloy, 7XXX aluminum alloys are especially widely used, such as in the aerospace and automobile field.At present,civil engineers and material scientists still have a large gap to fill in on the research of 7xxx aluminum alloys.In order to develop a reasonable extrusion, rolling and forging and other hot-processing technology, high temperature deformation and so requires much more work. In this work,the laws of microstructure and property evolution of 7A04 alloy on the different deformation temperature and times have been studied using the analysis method of room temperature tensile test,hardness test,OM observation,SEM.The purpose is to provide references for stipulating of the hot machining process, prediction and conformity of microstructure and property.The research result of deformation temperature shows that deformation temperature affect the microstructure and property of alloy. When 7A04 alloy is deformed on the temperature of less than 360℃, the hot deformation structure is mainly dynamic recovery structure. But when 7A04 alloy is deformed on the temperature of more than 400℃, recrystallization would occur. High temperature is beneficial for recrystallization. With the deformation temperature rose, thick second phase reduced, the strength, hardness and plastic of T5 alloy increased. After solution treatment, the second phase integrated into the matrix, then diffusion precipitated during aging. So with the deformation temperature rose, the strength and hardness of T6 alloy increased, but plastic first decreases then increase.The second phase and grain size of 7A04 aluminum alloy are affected by deformation times. When 7A04 alloy is deformed on the temperature of 320℃and 360℃, with the deformation times rose, second phase aggregate and distribute on the grain boundary. This complicates efforts to reduce solid solution strengthening and precipitation strengthening of alloying elements, so the strength and plastic both decreases. When 7A04 alloy is deformed on the temperature of more than 400℃, with the deformation times rose, the grain of alloy is thinning. Second phase integrates into the matrix in the the process of heating insulation on several times forming. The second phase will separate out in the cooling after deformation, so with the deformation times rose, the strength of T5 alloy increased, but plastic decreased; the strength and plastic of T6 alloy increased when deformation times is less than four times.When 7A04 aluminum alloy multiple deform at 320℃and 360℃, the static reply occured in the the process of heating insulation. But static reply and Static recrystallization occurred in the the process of heating insulation when alloy multiple deform more than 400℃.In this experiment, the best process of the 7A04 aluminum alloy is four times deformation in 480℃. After 470℃×45min+130℃×16h solution treatment and artificial aging, mechanical properties can be achieved:σb=590.9Mpa,σ0.2=532.5Mpa,δ=12.4%,ψ=18.3%.