【作者】 王强；

【导师】 唐建国； 王国军；

【作者基本信息】 中南大学 ， 先进制造（专业学位）， 2025， 博士

【摘要】 在国民经济建设中,铝合金材料需求量仅次于钢铁材料,被广泛应用在交通运输、海洋工程、航空航天等领域,尤其在空天装备的关键部件上,铝合金材料发挥着不可替代性的作用,随着现代航空航天等领域的持续发展,对铝合金材料的综合性能也提出了越来越高的要求。本文针对国家重大工程规划的超高强7136铝合金型材的研制任务,开展了该铝合金挤压材制备的工艺原理研究,为工业化材料的生产制备提供理论和实验依据,获得了以下主要结论:1、在7136超高强铝合金主成分（Al-8.4～9.4Zn-1.8～2.5Mg-1.9～2.5Cu）范围内,基于相图计算结果,运用等量析出成分优化设计方法,计算出了7136超高强铝合金成分范围的等量析出成分线（区）和动力学曲线（TTT曲线）,并进行实验性能验证,优选出了兼顾超高强度与低淬火敏感性的试制合金主成分（Al-9.0Zn-2.0Mg-2.0Cu）;揭示了7136超高强铝合金相组成规律:460℃时合金位于α（Al）+η（MgZn₂）相区,120℃时合金位于α（Al）+TAO（Al₃Cu₅Zn₂）+η（MgZn₂）相区,为该合金的热处理制度提供了理论依据。2、研究了7136超高强铝合金的高温热变形行为,构建了基于Zener-Hollomon参数高温本构模型,建立了合金的热加工图,确定了7136超高强铝合金热加工窗口:400℃～430℃、0.01s^-1～0.1s^-1。运用有限元模拟方法,研究了7136超高强铝合金目标型材的正、反挤压工艺,揭示了反向挤压型材的应变场和温度场均匀性优于正向挤压,不仅有利于型材组织性能的均匀性,还能改善型材挤压料头偏转问题。3、研究了固溶工艺对7136超高强铝合金组织性能的影响规律,探索了新型高温预析出工艺对型材组织性能的影响,揭示了双级固溶工艺450℃/2h+470℃/4h能够有效降低7136超高强铝合金挤压型材的再结晶程度,改善合金的耐腐蚀性能,使其强度和断裂韧性匹配更佳;发现了450℃/2h+470℃/4h+460℃/10min的高温预析出工艺能进一步改善7136超高强铝合金型材时效后性能的均匀性。4、研究了单级时效、双级时效和三级时效对超高强7136铝合金微观组织演变及强韧性和耐腐蚀性能的影响,优化出超高强、耐蚀的微结构组织模式,揭示了不同时效工艺对7136超高强铝合金晶内/晶界沉淀相析出演变的影响和性能的调控作用;发现了7136铝合金在120℃/24h+175℃/150min+120℃/24h的三级时效制度形成的微观组织模式具有最优的综合性能:晶内沉淀相平均尺寸在5nm～10nm之间,晶界无沉淀析出带（PFZ）宽度约为69nm,合金具备近似单级峰时效的晶内相均匀细小弥散的组织特征和双级过时效的晶界相断续分布的组织特征,合金强度和耐腐蚀性能匹配良好。5、研究了超高强7136铝合金大规格铸锭和大截面挤压型材工业化制备技术,采用Φ440mm规格工业化圆锭制备出了7136超高强铝合金目标型材,确定了7136超高强铝合金挤压材工业化生产控制要点,形成了稳定可靠的工艺规程,型材的抗拉强度、屈服强度和延伸率分别在650MPa、630MPa和14.0%以上,断裂韧性高于34.0MPa·m^1/2,且抗剥落腐蚀等级为EA级,各项性能明显优于现役最优的超高强7055铝合金挤压材。更多还原

【Abstract】 In national economic development,aluminum alloy ranks second only to steel in demand and is extensively utilized in transportation,marine engineering,and aerospace sectors.It plays an irreplaceable role in critical components of aerospace equipment,with increasingly stringent requirements for its comprehensive properties as modern aerospace technology advances.This study addresses the development of ultra-high-strength 7136 aluminum alloy profiles for national major engineering projects,investigating the processing principles for extruded materials to provide theoretical and experimental foundations for industrial production.The key findings include:Within the main composition range of ultra-high-strength 7136aluminum alloy（Al-8.4～9.4Zn-1.8～2.5Mg-1.9～2.5Cu）,the equivalent precipitation composition linesand time-temperature-transformation（TTT）curves were calculated using phase diagram analysis and an equivalent precipitation optimization design method.Experimental validation identified an optimal composition（Al-9.0Zn-2.0Mg-2.0Cu）balancing ultra-high strength and low quench sensitivity.The phase evolution was clarified:at 460℃,the alloy resides in theα（Al）+η（MgZn₂）phase region,while at 120℃,it transitions toα（Al）+TAO（Al₃Cu₅Zn₂）+η（MgZn₂）,providing a theoretical basis for heat treatment design.The high-temperature deformation behavior of ultra-high-strength7136 aluminum alloy was investigated.A constitutive model based on the Zener-Hollomon parameter was established,and a hot processing map was constructed,defining an optimal processing window of 400～430℃and 0.01～0.1s^-1.Finite element simulations of forward and backward extrusion processes revealed that backward extrusion achieves superior uniformity in strain and temperature fields compared to forward extrusion,enhancing microstructure homogeneity and mitigating billet head deflection.The effect of solution process on microstructure of ultra-high strength 7136 aluminum alloy extruded profiles was systematically studied,and the effect of new high temperature pre-precipitation process on microstructure was explored.A two-stage solution treatment（450℃/2h+470℃/4h）effectively reduced recrystallization and improved corrosion resistance,and a high-temperature pre-precipitation process（450℃/2h+470℃/4h+460℃/10min）further enhanced the uniformity of post-aging properties in extruded profiles.The effects of single-stage,double-stage,and triple-stage aging on intragranular/grain boundary precipitate behavior of ultra-high strength7136 aluminum alloy were systematically studied.The three-stage regression reaging process:（120℃/24h+175℃/150min+120℃/24h）yielded optimal microstructural characteristics:the size of precipitated phase is between 5～10nm,and the width of precipitate-free zones（PFZ）is 69nm,this microstructure combines the fine,homogeneous intragranular dispersion of peak-aged alloys with the discontinuous grain boundary features of over-aged alloys,achieving an excellent balance of strength and corrosion resistance.Industrial-scaleΦ440 mm billets were employed to fabricate 7136ultra-high-strength aluminum alloy profiles.Critical control parameters for extrusion were identified,and a robust production protocol was established.The extruded profiles exhibited tensile strength>650 MPa,yield strength>630 MPa,elongation>14.0%,fracture toughness>34.0MPa·m^1/2,and EA-grade exfoliation corrosion resistance,significantly outperforming the state-of-the-art 7055 ultra-high-strength aluminum alloy extrusions currently in service.更多还原