轧制态Al-6Zn-2Mg-2Cu合金时效过程的组织转变及析出动力学

发布时间：2018-03-06 10:37

本文选题：Al-6Zn-2Mg-2Cu　切入点：轧制变形　出处：《沈阳工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：Al-Zn-Mg-Cu高强铝合金具备良好的比强度、加工性能且性价比高等优势,普遍应用在各个领域,尤其是在航空航天事业和国防建设上。如今生产需求的日益紧迫,必须不停改善Al-Zn-Mg-Cu高强铝合金的组织形貌,来提高材料的力学性能。经轧制后的变形铝合金比铸造铝合金具有更优异的性能。本文以Al-6Zn-2Mg-2Cu高强铝合金为实验对象,通过热处理工艺与轧制工艺相结合的方法,将均匀化处理后的Al-6Zn-2Mg-2Cu铝合金进行不同变形量的轧制,而后进行T6时效处理。通过光学显微镜、扫描电镜、X射线衍射仪等实验设备对合金的微观组织进行观察分析,通过拉伸试验测试不同状态下材料的拉伸性能,用布洛维硬度计和数显显微硬度计分别对Al-6Zn-2Mg-2Cu铝合金宏观和微观硬度进行分析。研究了时效对轧制后铝合金MgZn_2相相析出动力学的影响。实验结果表明:Al-6Zn-2Mg-2Cu铝合金经20%轧制变形量时,晶界较平直,晶粒开始出现再结晶现象,部分保持粒状;40%轧制变形量时,晶粒沿轧制方向明显拉长,呈纤维状,内部出现再结晶晶粒。轧制后再经180℃单级时效,合金的强度、硬度与时效时间之间存在"双峰"的特征。20%轧制变形量的合金,第一时效峰出现在时效24h,其屈服强度为559MPa,抗拉强度为570MPa,硬度为146.97HB;第二时效峰出现在104h,其屈服强度、抗拉强度和硬度分别为569MPa、576MPa和139.88HB;40%轧制变形量的合金,第一时效峰出现在时效16h,其屈服强度为579MPa,抗拉强度为587MPa,硬度为151.87HB;第二时效峰出现在104h,其屈服强度、抗拉强度和硬度分别为592MPa、597MPa和130.03HB。在第一峰值时效时间内,随时效时间的延长,MgZn_2相的晶粒尺寸增大,最大没有超过32nm。时效的各个时间点40%轧制的合金第二相尺寸都比20%的大,8h后第二相的长大速率都下降,第二相的尺寸趋于平稳。轧制变形量为20%和40%的合金在180℃时效过程中,其MgZn_2相析出动力学的拟合方程分别为y=1-exp(-0.00060t~(0.5306))和y=1-exp(-0.00063t~(0.5276)),40%轧制的合金MgZn_2相析出动力学曲线的拟合程度高于20%轧制。
[Abstract]:Al-Zn-Mg-Cu high strength Aluminum Alloy good strength, processing performance and higher price advantage, widely used in various fields, especially in the aerospace industry and national defense construction. Now the production demand is increasingly urgent, must keep improving the microstructure of Al-Zn-Mg-Cu high strength Aluminum Alloy, to improve the mechanical properties of materials. The deformation of Aluminum Alloy after rolling than casting Aluminum Alloy has excellent performance. In this paper, Al-6Zn-2Mg-2Cu high strength Aluminum Alloy as the experimental object, through the method of process and rolling process combined with heat treatment, the Al-6Zn-2Mg-2Cu Aluminum Alloy after homogenization treatment of different rolling deformation, and then the T6 aging treatment. By optical microscope, scanning electron microscope. Observation and analysis of microstructure of alloy X ray diffraction experiment equipment, the tensile properties of tensile test materials under different conditions, With hardness meter and digital micro hardness tester respectively on Al-6Zn-2Mg-2Cu Aluminum Alloy macro and micro hardness were analyzed. The effect of aging on the rolling Aluminum Alloy MgZn_2 phase precipitation kinetics. The experimental results show that the Al-6Zn-2Mg-2Cu Aluminum Alloy by 20% rolling deformation, the grain boundary is flat, the grain recrystallization phenomenon began to appear, part keep the granular; deformation of 40% rolling, the grains are elongated along the rolling direction, fibrous, internal recrystallized grains. After rolling 180 C single aging, the strength of the alloy, the existence of "deformation characteristics of.20% rolling Shuangfeng" between hardness and aging time, aging peak appeared in the first time 24h, its yield strength is 559MPa, tensile strength 570MPa, hardness is 146.97HB; second aging peak appeared at 104H, the yield strength, tensile strength and hardness are respectively 569MPa, 576MPa and 139.88HB; 40% The rolling deformation of the alloy, the first aging peak in aging 16h, its yield strength is 579MPa, tensile strength 587MPa, hardness is 151.87HB; second aging peak appeared at 104H, the yield strength, tensile strength and hardness are respectively 592MPa, 597MPa and 130.03HB. in the first peak aging time, with prolonging of aging time. MgZn_2 phase alloy grain size increases, the size of the second phase maximum each time no more than 32nm. time 40% rolling than 20%, 8h growth rate of the second phase of the decline phase size stabilized. The rolling deformation is 20% and 40% in the process of ageing in alloy 180, fitting equation the kinetics of precipitation of MgZn_2 were y=1-exp (-0.00060t~ (0.5306)) and y=1-exp (-0.00063t~ (0.5276)), the fitting degree of 40% rolled alloy MgZn_2 precipitation kinetics curve is higher than that of the 20% rolling.

【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21;TG166.3

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