Gao Weihong;Fu Jinlai;Li Ting;Cong Fuguan;Sun Keqiang;Sun Bin;Fu Yudong;

• 1:School of Materials Science and Engineering
• 2: Harbin Engineering University
• 3:Northeast Light Alloy Co.
• 4: Ltd.

Abstract：

With the rapid development of aerospace industry in China,2324 aluminum alloy has been widely applied as acritical structural material for aircraft owing to its excellent fracture toughness and stress corrosion resistance.During solidification,rapid cooling leads to severe dendritic segregation and residual internal stress.The alloying elements are not uniformly distributed in the ingot and have large eutectic phases,which leads to a decrease in the mechanical properties of the alloy.Homogenization heat treatment can reduce compositional segregation and is considered an effective method for preparing uniform microstructures.This process can eliminate the internal stresses generated during casting and prevent the alloy from cracking in subsequent hot rolling.However,homogenization of high-strength aluminum alloys is difficult due to their high alloying element content.Therefor,investigating the diffusion behavior of elements is one of the most important topics to homogenize aluminum alloys.In this paper,the homogenization treatment of 2324 aluminum alloy was systematically studied through experiments,numerical simulations,and kinetic calculations,and the homogenization scheme was determined.The effects of different homogenization temperatures(480 and 490℃) and times(12,16,20 and 24 h) on micro structure were investigated by field emission scanning electron microscopy(SEM) and X-ray diffraction(XRD) using 2324 aluminum alloy ingots as the research object.The elemental diffusion behavior and kinetic process were investigated by Jmatpro simulation system.The results showed that severe segregation existed in the as-cast microstructure,and a large number of coarse eutectic phases distributed at the grain boundaries.Among them,the white phase was θ phase(Al_2Cu) and the black phase was S phase(Al_2CuMg).The eutectic phase in the as-cast structure had a greater influence on the properties of the alloy.During homogenization,the re-dissolution of eutectic phases at grain boundaries and intragranular regions was essentially the re-dissolution of alloying elements in eutectic phase;therefore,homogenization was dominatedby the diffusion of alloy atoms.Homogenization heat treatment reduced the quantity and size of segregated phases in the alloy.After homogenization at 480℃,partial segregated phases dissolved,while obvious dendritic segregated phases were still observed at the grain boundaries.At this time,the homogenization temperature of the alloy was low and the diffusion rate of alloying elements was relatively slow.Although the time was long,there were still a large number of eutectic phases with large sizes in the matrix.After homogenization heat treatment at 490℃ for 16 h,it was found that the quantity and size of internal segregated phases were significantly reduced.The segregated phases such as S phase(Al_2CuMg) and θ phase(Al_2Cu) had been fully dissolved,only a small amount of dendrites existed,and the degree of dendrite segregation was weakened.After homogenization treatment at 490℃ for 20 h,the dendritic precipitated phases could no longer be observed.In addition,the remaining eutectic phases were small and fine,and the dendritic segregation disappeared completely.Under the high temperature and long time homogenization treatment,the alloying elements in eutectic phase diffused into aluminum matrix,and the chemical composition of the matrix and grain boundaries gradually tended to be homogeneous.However,with the increase of temperature and time,some insoluble precipitated phases would gradually agglomerate and spheroidize,thus affecting the mechanical properties of the alloy.In summary,490℃ was analyzed as the homogenization temperature,the microstructure and chemical composition of the alloy was more uniform and the homogenization effect was better.But overburning might occur at higher temperatures.The heat treatment processes containing S phase included 480℃ for 12 h,480℃ for 16 h,480℃for 20 h,480℃ for 24 h,490℃ for 12 h,490℃ for 16 h,490℃ for 20 h,490 ℃ for 24 h.θ phase existed only under the heat treatment of 480℃ with holding times of 12,16,20,and 24 h.Therefore,the θ phase disappeared first during homogenization.The redissolution rate of S and θ phases increased with increasing temperature and time.By comparing the diffusion rates of elements between the dendrites,Mg element was the first to diffuse completely compared to Cu element.Combined with the homogenization kinetics to study the diffusion process of alloy elements between dendrites,consistent conclusions were obtained,and the homogenization process parameters of 2324 aluminum alloy were calculated to be 490℃ for 20 h.In conclusion,the best homogenization regime for 2324aluminum alloy suitable for industrialization was 490℃ for 20 h.

Key Words： aluminum alloys;dendrite segregation;homogenization treatment;kinetics

Abstract:

Keywords:

Foundation: 国家重点研发计划项目(2018YFB2001904);; 中央大学基金项目(3072021CFT1009);; 黑龙江省“百千万”工程科技重大专项(2019ZX10A01);; 黑龙江省自然科学基金项目(LH2021E029)资助

Authors: Gao Weihong;Fu Jinlai;Li Ting;Cong Fuguan;Sun Keqiang;Sun Bin;Fu Yudong;

DOI: 10.13373/j.cnki.cjrm.XY23030022

References：

• [1]Kumar N M S, Dhruthi, Pramod G, Samrat P,Sadashiva M. A critical review on heat treatment of aluminium alloys[J]. Materials Today:Proceedings,2022. doi:10.1016/j.matpr.2021.12.586.
• [2]Wang Z X, Li M Y, Han Q H, Yun X, Zhou K, Gardner L,Mazzolani F M. Structural fire behaviour of aluminium alloy structures:review and outlook[J]. Engineering Structures, 2022, 268:114746.
• [3]Zhang P, Liu J L, Gao Y R, Liu Z H, Mai Q Q. Effect of heat treatment process on the micro machinability of 7075aluminum alloy[J]. Vacuum, 2023, 207:111574.
• [4]Liu X T, Dong J, Cui J Z, Zhao G. Homogenization heat treatment of high-strength aluminum alloys[J]. Chinese Journal of Nonferrous Metals, 2003, 13(4):909.（刘晓涛，董杰，崔建忠，赵刚.高强铝合金均匀化热处理[J].中国有色金属学报，2003, 13(4):909.）
• [5]Zhong B, Hou S B, Yu Z Y, Xie J H, Zhang C W,Ding C. Influence of ultrasonic vibration on expansion forming process and quality for 6061 aluminum alloy tube[J]. Forging&Stamping Technology, 2025, 50(4):56.（钟斌，侯尚步，于正洋，谢佳昊，张传伟，丁春.超声振动对6061铝合金管材扩口成形过程及质量的影响[J].锻压技术，2025, 50(4):56.）
• [6]Wang D, Zhang W X, Huang S Q, Yi Y P, He H L.Effect of three-dimensional deformation at different temperatures on microstructure, strength, fracture toughness and corrosion resistance of 7A85 aluminum alloy[J]. Journal of Alloys and Compounds, 2022, 928:167200.
• [7]Wang Y W, Hou L G, Su H, Tian Q K, Yu K C, Eskin D,Katgerman L, Zhuang L Z. Tuning homogenization of high-strength aluminum alloys through thermodynamic alloying approach[J]. Materials&Design, 2022, 221:110975.
• [8]Yin J R, Chen J H, Cheng X X, Qiu Q Q, Wang W X,Weng Y Y. Micro-structure of Al-Cu alloys for automobile engines with multistage solution treatment and Sc microalloying[J]. Chinese Journal of Rare Metals,2025, 49(3):342.（殷嘉蓉，陈家浩，程翔翔，邱铨强，王文鑫，翁瑶瑶.多级固溶处理及Sc微合金化对汽车发动机用Al-Cu合金微观结构的影响[J].稀有金属，2025, 49(3):342.）
• [9]Lu W H, Wu X C, Yang N P, Wei Z Y, Huang Y L,Xu Z B, Tang H Q, Wang Y B, Jiang A K, Wang J S.Melt purification treatment, as-cast microstructure and mechanical properties of 6111 aluminum alloy with rareearth composite flux[J]. Chinese Journal of Rare Metals,2025, 49(8):1169.（陆维鸿，吴晓聪，杨南鹏，韦泽羽，黄杨林，许征兵，汤宏群，王友彬，蒋奥克，王俊升.稀土复合熔剂对6111铝合金熔体净化处理及其铸态组织与力学性能的影响[J].稀有金属，2025, 49(8):1169.）
• [10]Shan Z J, Liu S D, Ye L Y, Liu X D, Dong Y, Li Y R,Tang J G, Deng Y L, Zhang X M. Effect of three-stage homogenization on recrystallization and fatigue crack growth of 7020 aluminum alloy[J]. Journal of Materials Research and Technology, 2020, 9(6):13216.
• [11]Liu C, Luo B H, Wang C, Yang L. Study on the homogenization heat treatment of 2024 aluminum alloy[J]. Aluminum Processing, 2010,(4):8.（刘成，罗兵辉，王聪，杨磊. 2024铝合金的均匀化热处理研究[J].铝加工，2010,(4):8.）
• [12]Gupta A K, Gaunt P, Chaturvedi M C. The crystallography and morphology of the S'-phase precipitate in an Al(CuMg)alloy[J]. Philosophical Magazine A,1987, 55(3):375.
• [13]Li Z S, Pan F S, Wu H L, Chen Y R. Effect of homogenization treatment on the structure and properties of 7A55 aluminum alloy[J]. Journal of Aerospace Materials, 2011, 31(2):13.（李忠盛，潘复生，吴护林，陈韵如.均匀化处理对7A55铝合金组织与性能的影响[J].航空材料学报，2011, 31(2):13.）
• [14]Liu J D, Cao Z Q, Zhang H L, Li T J, Wang J C.Determination of homogenization process for 7050aluminum alloy[J]. Mechanical Engineering Materials,2009, 33(8):32.（刘吉东，曹志强，张红亮，李廷举，王家淳. 7050铝合金均匀化工艺的确定[J].机械工程材料，2009,33(8):32.）
• [15]Liu J T, Zhang Y, Liu J C, Ran F Q, Cui L. Analysis of casting microstructure and homogenization treatment of2324 aluminum alloy[J]. China High-Tech Enterprises,2016, 375(24):64.（刘俊涛，张义，刘君城，冉凡青，崔莉.浅析2324铝合金铸态组织及均匀化处理[J].中国高新技术企业，2016, 375(24):64.）
• [16]Wang S. Effect of Solution Treatment and Cold Rolling Deformation on Microstructure and Properties of Al-CuMg Alloy[D]. Harbin:Harbin University of Science and Technology, 2022. 1.（王帅.固溶处理与冷轧变形对Al-Cu-Mg合金组织与性能的影响[D].哈尔滨：哈尔滨理工大学，2022. 1.）
• [17]Lin G Y, Peng D S, Wei S M, Han H Y, Zhang H. Effect of strengthened solution treatment on microstructure of7075 aluminum alloy[J]. HTM, 2002, 27(11):30.（林高用，彭大暑，魏圣明，韩红阳，张辉.强化固溶处理对7075铝合金组织的影响[J].金属热处理，2002, 27(11):30.）
• [18]Sun K Q. Research on the Microstructural Transformation and Microscopic Mechanism of 2324 Aluminum Alloy during Heat Treatment Process Optimization based on Sheet Forming Process[D]. Harbin:Harbin Engineering University, 2022. 1.（孙克强.基于板材成型过程热处理工艺优化的2324铝合金组织转变及微观机制研究[D].哈尔滨：哈尔滨工程大学，2022. 1.）