Pb-Mg-10Al-0.5B合金高温流变行为及热挤压模拟

发布时间：2018-07-11 13:48

本文选题：Pb-Mg-10Al-0.5B + 合金　；参考：《昆明理工大学》2017年硕士论文

【摘要】：面对日益增长的能源需求与能源结构调整,大力发展绿色清洁能源是建立环境友好型社会和实现经济持续发展的必然选择。核反应堆的安全运行需要有效的核屏蔽材料作为保障,具有X射线,γ射线和中子辐射综合屏蔽材料的研制一直被作为重要科研课题受到各国重视。在Pb-Mg-Al-B系列合金中Pb-Mg-10A1-0.5B合金具有优异的力学性能以及屏蔽性能,其抗拉强度达到116MPa,对X射线的屏蔽率达到90%以上,对γ射线屏蔽率达到49%以上,对中子的屏蔽率达到90%以上。此外,Pb-Mg-10A1-0.5B合金的具有较小的平均腐蚀速度和腐蚀电流。但是由于该屏蔽材料存在大量的硬脆的低熔点金属间化合物,导致其塑性加工成形能力较差,严重制约了该屏蔽材料的推广和应用。为了探究Pb-Mg-10A1-0.5B合金的塑性变形理论和指导其热加工成形研究,本文利用Gleeble-3500D热模拟实验机对Pb-Mg-10A1-0.5B合金的高温流变行为进行了研究。利用线性拟合分析方法,研究了合金的高温塑性变形过程中的流变应力、应变、应变速率和温度的相互关系,建立了该屏蔽材料的流变应力本构模型;借助基于动态材料模型和Prasad失稳判据建立热加工图,结合微观组织,获得最佳工艺参数,同时还探讨了发生动态再结晶的临界条件;将流变应力数据和材料热物性参数耦合到MSC.Marc软件中,模拟了该屏蔽材料在热挤压过程中的应力分布、应变分布和温度分布,并研究分析了挤压条件对挤压过程的影响。结果表明:1.Pb-Mg-10A1-0.5B合金的应力-应变曲线表明合金具有明显的动态再结晶特征:压缩初始阶段,随着应变的增加,流变应力急剧增加达到峰值,随后缓慢下降直到稳态。应变速率一定时,流变应力随变形温度的升高而降低;变形温度一定时,流变应力随应变速率的增大而增大。2.根据双曲正弦模型,建立了 Pb-Mg-10A1-0.5B合金峰值应力本构模型,并且考虑到应变量可能对本构模型的影响,建立了应变量对方程参数的五次对应多项式,将应变量耦合入材料的高温变形本构模型,通过三种方法验证其准确性,其结果都能说明该模型具有很好的预测效果。3.通过Pb-Mg-10A1-0.5B合金的硬化率-应力曲线和硬化率-应变曲线得到该
[Abstract]:Facing the increasing demand for energy and the adjustment of energy structure, developing green clean energy is an inevitable choice to establish an environment-friendly society and achieve sustained economic development. The safe operation of nuclear reactors requires effective nuclear shielding materials as a guarantee, and the development of X ray, gamma ray and neutron radiation comprehensive shielding materials has been developed. In Pb-Mg-Al-B series alloy, the Pb-Mg-10A1-0.5B alloy has excellent mechanical properties and shielding properties, its tensile strength reaches 116MPa, the shielding rate of X ray is above 90%, the shielding rate of gamma ray is above 49%, and the shielding rate of neutron is above 90%. In addition, Pb-Mg-10A1-0 The.5B alloy has a small average corrosion rate and corrosion current. However, because the shielding material has a large number of hard and brittle low melting point intermetallic compounds, it causes poor plastic forming ability, which seriously restricts the popularization and application of the shielding material. In order to explore the plastic deformation theory of Pb-Mg-10A1-0.5B alloy and guide its heat. In this paper, the rheological behavior of Pb-Mg-10A1-0.5B alloy at high temperature was studied by Gleeble-3500D thermal simulation test machine. The relationship between the rheological stress, strain, strain rate and temperature in the high temperature plastic deformation process of the alloy was studied by using the linear fitting method. The rheological stress of the shielding material was established. The constitutive model, a thermal processing diagram based on dynamic material model and Prasad instability criterion, is established to obtain the best process parameters combined with microstructures. At the same time, the critical conditions for the occurrence of dynamic recrystallization are also discussed. The rheological stress data and material thermal properties are coupled to the MSC.Marc software, and the shielding material is simulated during the hot extrusion process. The stress distribution, strain distribution and temperature distribution, and the influence of extrusion conditions on the extrusion process are studied and analyzed. The results show that the stress strain curve of 1.Pb-Mg-10A1-0.5B alloy shows that the alloy has obvious dynamic recrystallization characteristics: the initial stage of compression, with the increase of strain, the rapid increase of the rheological stress to the peak, and then slow down. Down to steady state. When the strain rate is certain, the rheological stress decreases with the increase of the deformation temperature. When the deformation temperature is certain, the rheological stress increases with the increase of the strain rate and increases.2. according to the hyperbolic sinusoidal model. The peak stress constitutive model of the Pb-Mg-10A1-0.5B alloy is established, and the influence of the strain on the constitutive model is considered, and the effect of the strain on the constitutive model is considered. The five times corresponding polynomial of the equation parameters is applied to the equation, and the strain is coupled into the high temperature deformation constitutive model of the material. The accuracy of the model is verified by three methods. The results all show that the model has a good prediction effect.3. through the hardening rate stress curve and the hardening rate strain curve of the Pb-Mg-10A1-0.5B alloy.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.12

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