大变形应变诱导等温球晶化制备铝合金半固态坯料工艺研究

发布时间：2018-04-19 15:54

  本文选题：7005铝合金 + 半固态坯料　； 参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：随着轻量化、节能化的需求,7005铝合金结构件凭借其良好的理化性能被广泛应用到航空航天、机械、汽车、能源、国防等领域。目前,铝合金传统的成形加工技术有凝固成形和塑性成型两种,凝固成形结构件力学性能较差,塑性成形不能制造形状复杂结构件;金属半固态成形技术是一种近净成形技术,在制备高质量结构件的应用方面效果显著,7005铝合金的半固态成形技术也将会成为未来主流的金属成形方式。对于半固态金属成形技术,制备高质量的半固态坯料是关键,本文采用等通道往复挤压与等温处理两个过程实现大变形应变诱导等温球晶化方法制备7005铝合金半固态坯料,研究挤压温度、热处理、等温温度、等温时间等参数对材料微观组织和力学性能的影响规律,探索坯料制备的最佳工艺参数。本文通过Deform-3D软件对等通道往复挤压过程进行模拟仿真,得到在不同冲头位移时,材料应力、应变的变化情况;同时也对不同挤压温度、叠加坯料挤压等状态进行模拟仿真。分析发现:挤压过程中,材料的应力、应变随着冲头位移的增加而增加;随着挤压温度的升高,材料的应力、应变减小,且应力集中区域变小;叠加坯料挤压时,坯料间接触处产生了畸形应变和应力集中区域。通过等通道往复挤压工艺对铸态7005铝合金进行晶粒细化处理,借助金相显微镜、拉伸试验机、电子背散射衍射(EBSD)技术、扫描电镜(SEM)对挤压过程中材料微观组织形貌、组成和力学性能进行测试分析,研究各参数对坯料微观组织和力学性能的影响规律;研究表明:经过等通道往复挤压后,坯料晶粒细化明显,晶粒致密度增加,材料力学性能提高;叠加坯料挤压实验中,随着变形量的增加,材料晶粒细化效果更佳;连续挤压实验则表明,随着挤压温度的增加,坯料晶粒尺寸先减小后增大,在挤压温度为400℃时挤压晶粒细化效果更好。将挤压后的坯料加热到半固态温度进行等温处理实验,利用金相显微镜、IPP图像处理软件、能谱分析仪(EDS)等设备,观察并分析材料微观组织在等温处理过程中的演变规律。分析发现,随着等温温度和等温时间的增加,晶粒尺寸和形状系数保持增加,但温度较高时,晶粒平均直径减小;Fe、Mn、Cu等元素形成共晶相,在等温处理过程中先熔化形成液相。得出最佳工艺参数:挤压温度为400℃,材料在610℃保温20min或在615℃保温15min。在对等温处理过程分析的基础上,提出大变形应变诱导等温球晶化制备7005铝合金半固态坯料的新方法。
[Abstract]:With the light weight and energy saving demand, the aluminum alloy structural parts have been widely used in aerospace, machinery, automobile, energy, national defense and other fields with its good physical and chemical properties.At present, the traditional forming technology of aluminum alloy includes solidification forming and plastic forming, the mechanical properties of solidified forming structural parts are poor, and plastic forming can not make complex structural parts, the metal semi-solid forming technology is a kind of near net forming technology.The semisolid forming technology of 7005 aluminum alloy, which has remarkable effect in the preparation of high quality structural parts, will also become the mainstream metal forming method in the future.For the semisolid metal forming technology, the preparation of high quality semi-solid billets is the key. In this paper, 7005 aluminum alloy semi-solid billets are prepared by means of large strain induced isothermal spheroidization by equal channel reciprocating extrusion and isothermal treatment.The effects of extrusion temperature, heat treatment, isothermal temperature and isothermal time on the microstructure and mechanical properties of the material were studied.In this paper, the process of reciprocating extrusion with equal channel is simulated by Deform-3D software, and the change of material stress and strain under different punch displacement is obtained. At the same time, the state of extrusion temperature and superposition billet extrusion are simulated.It is found that the stress and strain of the material increase with the increase of the punch displacement during extrusion, the stress and strain of the material decrease with the increase of extrusion temperature, and the stress concentration area becomes smaller.The abnormal strain and stress concentration area are produced at the contact between the billets.The grain size of as-cast 7005 aluminum alloy was refined by the equal channel reciprocating extrusion process. The microstructure and morphology of the as-cast 7005 aluminum alloy were studied by means of metallographic microscope, tensile testing machine, electron backscatter diffraction (EBSD) technique and scanning electron microscope (SEM).The composition and mechanical properties were tested and analyzed, and the effects of various parameters on the microstructure and mechanical properties of the billet were studied.In the superposition blank extrusion experiment, the grain refinement effect is better with the increase of deformation, and the continuous extrusion experiment shows that the grain size of the blank decreases first and then increases with the increase of extrusion temperature.When the extrusion temperature is 400 鈩，

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