Effect Of Isothermal Heat Treatment And Compressive Deformation On Microstructure And Properties Of 2024 Aluminum Alloy In Solid-liquid Two-Phase Zone

Semi-solid forming technology is an advanced forming technology,which has the advantages of being significantly different from traditional solid plastic forming and liquid forming.However,the conventional extrusion process has the disadvantages of low efficiency and large deformation resistance when extruding high-strength aluminum alloy.The semi-solid extrusion process is used to optimize the extrusion process of high-strength aluminum alloy.The solid-liquid two-phase zone isothermal heat treatment method applied to the semi-solid extrusion can eliminate the semi-solid billet preparation and secondary heating,and shorten the process flow.The specific research contents include:(1)Studying the evolution of 2024 aluminum alloy structure and the changes of phases and elements in the alloy during the isothermal heat treatment of solid-liquid two-phase zone.(2)Exploring the compressive strain mechanical behavior and microstructure change law of 2024 aluminum alloy in solid-liquid two-phase zone during isothermal compression.The results show that:(1)in the solid-liquid two-phase zone isothermal heat treatment,as the temperature increases,the spheroidization process of the crystal grains accelerates,and the liquid phase rate increases.When the heat preservation temperature is the same,with the heat preservation The time is prolonged,the grains are spheroidized and merged and grown,and the liquid phase rate increases.(2)In the process of non-dendritic transformation in solid-liquid two-phase zone isothermal heat treatment,the main eutectic phase in 2024 aluminum alloy does not change,still Al2Cu phase and Al2CuMg phase.Al2Cu phase increases Al2CuMg phase with increasing temperature cut back.When the temperature is 5 min at 595?,the Al2CuMg phase disappears almost.With the increase of isothermal heat treatment temperature,the Cu,Mg and Al elements in the 2024 aluminum alloy will be more evenly distributed,and the segregation will gradually disappear,but the grain boundary will disappear.The increase in liquid phase,Cu,Mg,Al segregation will be more serious.(3)2024 aluminum alloy in the solid-liquid phase phase isothermal heat treatment compression deformation,when the deformation temperature is the same,the alloy deformation resistance increases with the decrease of the compression rate,when the compression rate is the same,the alloy deformation resistance with the temperature The increase and decrease,especially when the solidus line is reached,the stress will drop significantly.(4)When compressively deformed in a semi-solid state,the 2024 aluminum alloy is mainly a solid phase skeleton fracture,a liquid phase flow,and sliding rotation and deformation of solid phase particles.In the semi-solid state,as the compression temperature increases,the degree of grain deformation of the core of the 2024 aluminum alloy sample is smaller,and the flow becomes more uniform along the vertical compression direction.