【作者】 李楠；

【导师】 邢书明；

【作者基本信息】 北京交通大学 ， 车辆工程， 2013， 博士

【摘要】 摘要：泡沫铝合金是一种具有孔状结构的轻质功能材料,具有低密度、高强韧、耐冲击、高比强度、高比刚度、高效散热、隔热、阻燃等一系列独特性能。先驱体是采用二步法制备泡沫铝合金的必备原料。论文以获得含有均匀分布发泡剂的先驱体为目标,提出了一种泡沫金属先驱体制备的新方法——半固态熔体搅拌法,并围绕这一制备技术,开展了如下研究：(1)设计研究和制造了半固态熔体搅拌法制备泡沫铝合金先驱体的试验装置。该装置包括能够促进发泡剂均匀分布的机械搅拌装置、能够直接高效地添加发泡剂的添加器、先驱体的快速取样装置、加热系统、以及数据采集系统五部分。(2)提出了基于数字图像技术的泡沫铝合金先驱体及泡沫铝合金件的内部结构和质量的表征与评价技术。重点研究了泡沫铝合金先驱体试样的处理、图像采集、处理和分析方法,并综合竖直和水平两个方向的数字化评价,获得先驱体质量的三维评价体系,该体系可以定量表征先驱体和泡沫铝合金中发泡剂及气孔的大小、数量和三维分布,能够定量表征发泡剂的集聚和团簇程度,能够客观、准确地反映先驱体的质量优劣及缺陷位置,为泡沫铝合金等多孔材料的质量综合评价提供了一种较为准确的方法。(3)研究得到了合金成分、搅拌温度、搅拌表观黏度、搅拌时间等工艺参数对发泡剂在先驱体中的分布、分解情况以及初生气泡的形貌尺寸及分布状况的影响规律,最终形成制备含有均匀分布发泡剂的铝合金先驱体制备工艺方案。(4)研究了发泡剂在半固态熔体搅拌混合过程的分解和气泡的长大行为,建立了气泡的长大模型,探讨了半固态熔体约束条件下气泡的极限尺寸及影响因素,并导出了半固态条件下初生气泡尺寸的控制模型,为先驱体内发泡剂分布和预发气泡的控制提供了依据。本论文提出的制备和评价方法对于降低先驱体制备成本、提高制备效率及泡沫铝质量,进而加速泡沫金属的产业化应用步伐具有重要的参考价值。今后还需加强这一技术的工程化应用研究,扩大其应用范围。图86幅,表9个,参考文献103篇。更多还原

【Abstract】 ABSTRACT:Metal foam is a lightweight functional material with series of performances such as hole-like structure, low-density, high-toughness, high impact resistance, high specific strength, high stiffness, efficient cooling, insulation, fire-retardant and etc. Precursor is the basic and only raw material for the two-step processing of metal foam. The aim of this paper to propose a new approach to obtain the precursor with uniform distributing blowing agents-processing precursor by semi-solid melt stirring, and the following researches were carried out about this approach:(1) The equipment of processing aluminum precursor was designed and manufactured which to obtain precursor by semi-solid melt stirring method. The equipment includes five main parts:the stirring part which to distribute blowing agents by mechanical stirring; the adding part which is adding to add blowing agents directly and efficiently, the sampling part which to obtain precursor samples, the controlling part which to adjust temperature and the data part which to collect the experiments’datas.(2) The characterization and evaluation method for quality and internal sturcture of both aluminum precursors and metal foam parts was proposed through diagital image technology. The main researches were focused on precursor sample treatment, image acquisition, image handling and data analysis. And it is to obtain the digital evaluation of precursor on both vertical and horizontal directions as well as the three-dimensional evaluation system. This3D system could quantitatively characterize the blowing agents or pores in precursors and aluminum foam by size, quantity and the three-dimensional distribution. Also this system could characterize agglomeration and degree of cluster of blowing agents, which could indicate objectively and accurately the quality of the precursor and defect locations. This3D system provided an alternative method for the quality evaluation of both precursor and metal foam parts.(3) The distribution and decomposition effects on blowing agents and the initial bubbles morphology in precursors were studied by changing processing parameters such as alloy composition, stirring temperature, stirring apparent viscosity, stirring time and quantity of blowing agents, and the technique of processing aluminum precursors with uniformly distributed blowing agents inside was carried out ultimately.(4)The decomposition behaviors of blowing agents as well as the growing behavior of intial bubbles in the semi-solid melt during stirring were studied in this paper. A growing model of bubbles in semi-solid melt was established, which exports the control model of the limit bubble size and its impacting factors in the semi-solid melt. And this model provided basises for the control of intial bubbles and blowing agents distribution in the procursor.This processing and evaluation methods presented by this paper were of reference value for reducing the cost of processing aluminum precursor, improving production efficiency and quality of the aluminum foam, even accelerating the pace of industrial applications of the metal foam. And the author believed that the engineering applications of this technology need to be strengthened in the future so as to expand the scope of its application.更多还原