【作者】 王战锋；

【导师】 张辉；

【作者基本信息】 湖南大学 ， 材料加工工程， 2007， 硕士

【摘要】 喷射沉积坯通常含有一定量的孔隙,作为结构件直接使用时性能比较差,其最终能否得到成功的应用,取决于制坯后的致密化加工过程中所获得的性能。因此,为了获得所要求力学性能,必须对喷射沉积坯进行后续塑性加工使其致密化。但采用挤压、旋压、锻造、轧制等技术,由于受加工方式及压力设备等的限制通常难以实现大型坯件的致密化加工。而采用楔形压制装置,可在小吨位压力机上通过局部变形、多道次小变形累积实现大变形,大大降低了喷射沉积材料后续致密化加工成本,解决了制备大件的难题。本文主要研究内容有:1.对喷射沉积5A06铝合金多孔材料高温压缩变形行为及显微组织演变进行了研究。建立了喷射沉积5A06铝合金热压缩变形流变应力的本构方程,将流变应力模型计算值与实测值进行比较,结果较为精确,为有限元数值模拟分析提供了数学模型。2.对热压缩后显微组织进行了金相分析和硬度测试,初步探明了孔洞及材料硬度同温度和应变速率的关系。3.本文还建立了单轴压缩时相对密度与高向变形量之间的理论关系,并用有限元模拟了单轴热压缩过程,结果显示理论公式与模拟结果和实验结果三者吻合较好,互相佐证。4.借助于有限元软件,文中针对大尺寸喷射沉积坯料研究了楔形压制实验中不同的压制温度和压制速度以及压制方式等相关工艺参数对变形与致密化的影响,结果表明:双面楔压可有效提高致密化效果,合理的楔压温度是450℃~500℃,合理的楔压速度是0.5~1.0mm/s。更多还原

【Abstract】 The spray deposited performs usually contain a certain quantity of porosity, thus have the poor property when using directly. Whether this material would be using well or not lies on the property after the densification. Therefore to get a required mechanical characteristics, the porous performs must be further dandified and deformed plastically. The traditional technology such as extrusion, screw pressing, forging, rolling can not get full dense material, however new technology named cyclic pressing was used to density the spray deposited 5A06 aluminum alloy, in which the large deformation can be obtained through the sum-up of local deformation. This method can also solve the problems in traditional process and greatly reduce the producing cost of the post-densification. The main researches in this study are as follows:1. A study on the behavior of hot compression of spray-deposited 5A06 aluminum alloy were performed. A constitutive equation was established by analyzing the relationships of the flow stress and the strain and the deformation temperatures and strain rates。The flow stress during hot compression can be described by the hyperbolic sine relation of Zener-Hollomon parameter Z. The proposed equation gives a good agreement with the measured values, which consequently can be as the numeric-simulated flow stress model of spray-deposited 5A06 aluminum alloy during hot deformation。2. In this study, the changes of the microstructure and the hardness have revealed the relationships of temperatures and the strain rates.3. A theoretic relationship to relative density and high reduction was established in the single axial compress, the results of FEM show that the theory values and the FEM results give a good agreement with the measured values.4. By the finite element software, the effects of the different process parameters on the deformation and densification in the cyclic pressing were researched. The results show that the two face cyclic pressing is needed and the reasonable temperature is 450℃~500℃, the reasonable velocity is0.5~ 1.0mm/s.更多还原