【作者】 张飞；

【导师】 王晓溪； 高仕恒；

【作者基本信息】 盐城工学院 ， 机械（专业学位）， 2025， 硕士

【摘要】 随着科学技术的不断发展和各种新兴技术、新产业的出现,对金属材料性能要求越来越高,单一金属材料的性能难以胜任现代工程设备的需求。双金属复合材料依靠材料的“互补效应”,充分发挥基体金属的优势,从而实现性能的协同提升。近年来,双金属复合材料的生产、研究和应用越来越引起人们的注意。钛具有较高的比强度、优良的耐腐蚀性、耐磨性和抗疲劳性,但较高的成本限制其应用范围。铝具有密度低,比强度高和来源广泛等优点,但是其耐磨性不佳,抗冲击能力较差。通过双金属复合工艺制备的钛铝双金属复合材料可以弥补两种金属的短板,既可以降低成本又可以获得纯铝不具备的力学性能。但是传统钛铝双金属复合工艺操作危险且复合效果不理想,这阻碍了钛铝双金属复合材料的大规模生产和应用。本文以钛铝双金属复合棒材为对象,采用数值模拟与工艺实验相结合的研究方法,利用新型大塑性变形工艺等通道转角膨胀挤压（Expansion Equal Channel Angular Pressing,Exp-ECAP）在450℃条件下制备钛铝双金属复合棒材,研究了工艺参数对钛铝双金属复合棒材界面结合行为及力学性能的影响。建立了钛铝双金属复合棒材Exp-ECAP变形有限元模型,通过DEFORM-3D有限元分析软件对钛铝双金属复合棒材Exp-ECAP变形过程进行模拟,分析了挤压载荷、等效应变、等效应力、损伤参数等场量在变形过程中的分布规律,发现Exp-ECAP工艺由于耦合了镦、剪、挤三种变形方式,使得坯料温度在变形时整体升高且降低了塑性差异,能够使钛铝双金属复合棒材更容易达到协调变形。根据Cockcroft-Latham断裂准则预测得到Exp-ECAP工艺能够无损伤制备钛铝双金属复合棒材。利用自行设计模具及工装完成钛铝双金属复合棒材在450℃条件下Exp-ECAP和ECAP工艺的无损伤制备,结合扫描电镜、能谱分析和X射线衍射等表征分析手段观察620℃×4 h退火后不同工艺处理的坯料界面结合处微观组织。实验结果表明,退火后在界面扩散层均是由TiAl、TiAl₃和少量的Ti₂Al₅组成。通过力学性能测试退火两种工艺界面组织性能,结果表明,Exp-ECAP工艺钛铝双金属复合棒材结合效果良好,剪切强度较ECAP工艺处理的坯料提升9%。对坯料进行不同工艺参数下（580℃×4 h、600℃×4 h、620℃×4 h、620℃×2h、620℃×8 h）的退火实验。实验结果揭示,随着退火温度的提升,界面扩散层的厚度由1.36μm（580℃）增长至4.27μm（620℃）,在此过程中,两基体金属的微观硬度保持稳定,未见显著变化,界面结合处的硬度始终处于两侧基体硬度之间,并且随着退火温度的增加,界面化合物保持一致。剪切强度从10.3 MPa（580℃）提升至13.7 MPa（620℃）。随着退火时间的增加,界面扩散层厚度2.26μm（2 h）增长至8.26μm（8 h）,钛侧显微硬度由171.4 HV下降至145.6 HV,铝侧显微硬度由25.1 HV下降至20.1 HV,界面扩散层硬度从33.7 HV（2 h）迅速增长至85.2 HV（4 h）,再缓慢增长至96.2 HV（8 h）,剪切强度随着时间匀速增长,从12.7 MPa（2 h）增长至14.7 MPa（8 h）。从生长动力学分析,界面扩散层的生长动力学方程为:x=0.99（t-t₀）。综上所述,本研究通过数值模拟与工艺实验相结合的方法,系统研究了Exp-ECAP工艺制备钛铝双金属复合棒材的界面结合行为及力学性能。结果表明,Exp-ECAP工艺能够有效降低钛铝双金属的塑性差异,促进协调变形,通过退火处理能够有效地改善坯料界面组织性能。退火温度和时间的增加均能促进界面扩散层的生长,同时优化界面化合物的分布,从而提升剪切强度。此外,界面扩散层的生长动力学方程为研究提供了理论依据。这些发现为钛铝双金属复合材料的制备工艺优化及性能提升提供了重要的实验和理论支持,具有广泛的应用前景。更多还原

【Abstract】 With the continuous development of science and technology and the emergence of various emerging technologies and industries,the performance requirements for metallic materials are becoming increasingly demanding.Single metallic materials often struggle to meet the needs of modern engineering equipment.Bimetal composite materials,relying on the"complementary effect"of materials,fully leverage the advantages of the base metals,there by achieving performance improvements.In recent years,the production,research,and application of bimetal composite materials have gained increasing attention.Titanium boasts high specific strength,excellent corrosion resistance,wear resistance,and fatigue resistance,but its high cost limits its application range.Aluminum,on the other hand,offers low density,high specific strength,and abundant availability,but it suffers from poor wear resistance and impact resistance.Titanium-aluminum bimetal composite materials,prepared through bimetal composite processes,can compensate for the shortcomings of both metals,reducing costs while achieving mechanical properties that pure aluminum lacks.However,traditional titanium-aluminum bimetal composite processes are hazardous and yield unsatisfactory bonding performance,hindering the large-scale production and application of titanium-aluminum bimetal composite materials.This dissertation focuses on titanium-aluminum bimetal composite rods,employing a research method that combines numerical simulation with process experiments.Using the novel severe plastic deformation process of Expansion Equal Channel Angular Pressing（Exp-ECAP）,titanium-aluminum bimetal composite rods were prepared at450℃.The study investigates the effects of process parameters on the interface bonding behavior and mechanical properties of titanium-aluminum bimetal composite rods.A finite element model for the Exp-ECAP deformation of titanium-aluminum bimetal composite rods was established.The DEFORM-3D finite element analysis software was used to simulate the Exp-ECAP process of titanium-aluminum bimetal composite rods.The distribution of extrusion load,effective strain,effective stress,and damage parameters during deformation were analyzed.It was found that the Exp-ECAP process,by coupling upsetting,shearing,and extrusion deformation modes,increases the overall temperature of the billet during deformation and reduces plasticity differences,making it easier for titanium-aluminum bimetal composite rods to achieve coordinated deformation.According to the Cockcroft-Latham fracture criterion,the Exp-ECAP process can prepare titanium-aluminum bimetal composite rods without damage.Using self-designed dies and tooling,titanium-aluminum bimetal composite rods were successfully prepared at 450℃using both Exp-ECAP and ECAP processes without damage.Characterization techniques such as scanning electron microscopy（SEM）,energy-dispersive spectroscopy（EDS）,and X-ray diffraction（XRD）were employed to observe the microstructure of the interface bonding area of billets treated with different processes after annealing at 620℃for 4 hours.Experimental results showed that after annealing,the interface diffusion layer consisted of TiAl,TiAl₃,and a small amount of Ti₂Al₅.Mechanical property tests on the interface microstructure of both processes after annealing revealed that the Exp-ECAP process resulted in excellent bonding of titanium-aluminum bimetal composite rods,with shear strength increasing by 9%compared to billets treated with the ECAP process.Annealing experiments were conducted on billets under different process parameters（580℃×4 h,600℃×4 h,620℃×4 h,620℃×2 h,620℃×8 h）.The results indicated that as the annealing temperature increased,the thickness of the interface diffusion layer grew from 1.36μm（580℃）to 4.27μm（620℃）.During this process,the microhardness of the two base metals remained stable without significant changes,and the hardness at the interface bonding area consistently fell between the hardness of the two base metals.The interface compounds remained consistent as the annealing temperature increased.Shear strength increased from 10.3 MPa（580℃）to 13.7 MPa（620℃）.As the annealing time increased,the thickness of the interface diffusion layer grew from 2.26μm（2 h）to8.26μm（8 h）.The base metal undergoes continuous dynamic recrystallization and stress relaxation within its microstructure,leading to a gradual decline in microhardness.The microhardness on the titanium side decreased from 171.4 HV to 145.6 HV,while on the aluminum side,it decreased from 25.1 HV to 20.1 HV.The hardness of the interface diffusion layer increased rapidly from 33.7 HV（2 h）to 85.2 HV（4 h）,then slowly to 96.2HV（8 h）.Shear strength increased steadily over time,from 12.7 MPa（2 h）to 14.7 MPa（8 h）.From the growth kinetics analysis,the growth kinetics equation for the interface diffusion layer is:x=0.99（t-t₀）.In summary,this study systematically investigated the interface bonding behavior and mechanical properties of titanium-aluminum bimetal composite rods prepared using the Exp-ECAP process through a combination of numerical simulation and process experiments.The results demonstrate that the Exp-ECAP process effectively reduces the plasticity differences between titanium and aluminum,promoting coordinated deformation.Annealing treatment can significantly improve the interface microstructure and properties of the billets.Both increasing annealing temperature and time promote the growth of the interface diffusion layer while optimizing the distribution of interface compounds,thereby enhancing shear strength.Additionally,the growth kinetics equation of the interface diffusion layer provides a theoretical basis for further research.These findings offer important experimental and theoretical support for the optimization of preparation processes and performance enhancement of titanium-aluminum bimetal composite materials,with broad application prospects.更多还原