泡沫铝制备与其压缩性能研究

采用粉末致密化发泡（PCF）工艺制备了泡沫纯铝,对制备过程及影响孔结构的因素进行了分析.系统研究了压力、发泡温度、发泡时间、发泡剂含量和粒度对泡沫纯铝结构变化的影响规律,用自行设计的软件FoamScan对孔结构进行了描述.得出了试验条件下的优化工艺参数配置.进行了泡沫铝压缩性能测试,通过理论模型、性能测试数据作图对比的方法获得了孔隙率83%～87%泡沫纯铝的屈服强度表达式.确定了泡沫纯铝的制备工艺、结构、性能的相互关系.     

造孔剂法制备泡沫钛的研究现状与进展

泡沫钛融合了泡沫结构与金属钛的双重属性，具有出色的力学性能、优异的耐腐蚀性和良好的生物相容性等优点，在航空、航天、海洋工程、生物医学、能源与环保等领域应用前景广阔。基于粉末冶金技术的造孔剂法是目前制备泡沫钛的主流方法，不仅具有操作简单、设备要求低的优点，而且能通过调整造孔剂参数来控制最终制品的结构与性能。本文综述了造孔剂法制备泡沫钛领域的研究现状与进展，通过分析文献、整理数据，讨论了高孔隙率泡沫钛的研究历程和瓶颈问题，指出了泡沫钛孔隙率研究的发展趋势。     

粉末冶金法制备通孔泡沫铝

通孔多孔金属材料具有良好的性能，被广泛用于各个领域。文章采用粉末烧结法制备了铝多孔泡沫金属材料，并对材料制备过程的工艺参数及材料的孔结构进行了初步的研究。     

闭孔胞状泡沫铝的单向压缩力学性能和吸能能力

通过不同孔隙度闭孔胞状泡沫铝的准静态压缩试验,研究泡沫铝孔隙度对其力学性能和吸能能力的影响。闭孔胞状泡沫铝单轴压缩应力应变曲线呈现明显的3个阶段:线性变形、平台阶段、致密化阶段;在单向压缩情况下,泡沫铝的压缩强度、吸能能力随着孔隙度的增大而减小;采用Gibson-Ashby的模型分析闭孔胞状泡沫铝的压缩屈服强度,并提出泡沫铝吸能能力公式,为工程应用提供理论支持。     

熔体发泡法制备泡沫鋁的缺陷分析

以TiH2作发泡剂，采用熔体发泡法通过控制发泡温度、保温时间、搅拌速度、冷却方式及各种添加剂含量，成功制备出孔结构基本均匀，孔隙率为60％～85％、平均孔径〈3mm泡沫铝样品。重点分析了泡沫铝制备过程中对孔结构稳定性和均匀性影响因素，针对泡沫铝常见缺陷（缩孔、裂纹、局部大孔），出现的原因提出改进措施。     

冷压-溶解-真空烧结法制备泡沫铝的阻尼性能研究

采用冷压-溶解-真空烧结法制备泡沫铝，并用单自由度稳态正弦激励法对制备的不同孔隙度及不同孔径的泡沫铝的阻尼性能进行了研究，讨论了加入Y2O3对泡沫铝阻尼性能和力学性能的影响。结果表明：泡沫铝的阻尼性能随着孔隙度的增加而增加，随着孔径的增大而减小；加入适量的Y2O3可以改善泡沫铝的阻尼性能和力学性能，当Y2O3加入的质量分数为0．5％～0．8％时泡沫铝达到了最佳的阻尼性能和力学性能，但过量的Y2O3将导致阻尼性能和力学性能降低。     

反重力渗流铸造法制备开孔泡沫铝材料

采用反重力渗流铸造法成功制备了开孔泡沫铝材料,分析了材料的准静态压缩性能及主要制备工艺参数与开孔泡沫铝空隙度之间的关系。研究结果表明：采用反重力渗流铸造法所制备的泡沫铝几乎没有宏观缺陷,孔洞分布均匀、孔壁结构完整;泡沫铝的空隙度对其压缩性能的影响很大,泡沫铝的屈服强度与平台应力均随空隙度的降低而升高;提高粒子预热温度、增大保压压力或延长保压时间,均有助于降低空隙度。     

PCM法泡沫铝的研究及应用现状

介绍了PCM法制备泡沫铝的国内外研究现状，讨论了一些因素对泡沫铝发泡行为及其孔结构的影响。并对PCM法大尺寸泡沫铝及复合结构的制备、应用做了介绍。最后对PCM法制备泡沫铝今后的发展方向和现存问题做了分析。     

放电等离子烧结溶解法制备SiC/Al复合泡沫 材料及其压缩性能

以纯铝为基体,NaCl作为造孔剂,粒径为20μm的SiC颗粒为增强相,采用放电等离子烧结溶解法制备SiC/Al复合泡沫。用SEM、EDS对其微观形貌进行表征,并对该复合泡沫材料进行压缩实验,研究其室温下的压缩性能.结果表明:在真空状态下,采用烧结温度550℃,外加压力30 MPa,保温时间10min,能够制备出致密度在97. 6%,性能优异的SiC/Al复合泡沫材料.与纯泡沫铝相比,SiC/Al复合泡沫的强度高,当SiC的添加量(质量分数)为10%时,SiC/Al复合泡沫的强度为58 MPa,增长幅度为82. 76%.     

Ni-Cr-Co-W-Mo-Al-Ti合金制备多孔材料的组织与性能研究

用粉末烧结法制备了孔结构为球形中空孔和线型中空孔的镍基多孔高温合金材料.对试样进行显微组织观察和力学性能测试.结果表明:制备的多孔高温合金材料的孔隙分布均匀,孔径大小一致.通过高温烧结,多孔合金骨架处的金属颗粒之间形成了烧结颈,发生了烧结结合.生成孔的孔隙度随造孔剂(尿素)的添加量增加而增加,当造孔剂的质量分数为40%时,可得到孔隙度为81.62%的球形多孔材料.多孔材料具有优良的能量吸收性能,其压缩性能随孔隙度和孔径的增加而下降.     

Acoustic Emission Analysis of Damage during Compressive Deformation of Amorphous Zr-Based Foams with Aligned, Elongated Pores

Acoustic emission methods are used to investigate the evolution of internal microfractural damage during uniaxial compression of amorphous Zr-based foams with aligned, elongated pores. The foams are fabricated by means of densifying a blend of crystalline W powders and amorphous Zr-based powders with two oxygen contents (0.078 and 0.144 wt pct) by warm equal channel angular extrusion, followed by dissolution of the elongated W phase from the fully densified amorphous matrix. For the high-oxygen foams, prior powder boundaries in the amorphous struts promote damage that accumulates during compression, resulting in energy-absorbing properties comparable with the low-oxygen foams without stress-concentrating powder boundaries. The influence of pore orientation on the evolution of microfracture damage and the ability of the foams to accumulate damage without catastrophic failure is also investigated: pores oriented from 24 to 68 deg to the loading direction promote wall bending, resulting in foams with more diffuse damage and better energy-absorbing properties.     

基于PCM法泡沫铝制备工艺的控制及发展

介绍了粉末冶金压制法制备泡沫铝的国内外研究现状,讨论了一些因素对PCM法制备泡沫铝发泡行为及其孔结构的影响。并对PCM法制备大尺寸泡沫铝的工艺做了介绍。最后对PCM法制备泡沫铝合金今后的发展方向和现存问题做了分析。     

PCM法泡沫铝合金的研究现状

介绍了泡沫铝的国内外研究现状和改善泡沫铝合金性能的途径,讨论了一些因素对PCM法制备泡沫铝发泡行为及其孔结构的影响。这些因素包括预制体制备方式、粉体颗粒粒度、TiH2的分解特性和冷却方式。并对PCM法制备泡沫铝合金今后的发展方向和现存问题做了分析。     

Deformation Behavior Estimation of Aluminum Foam by X-ray CT Image-based Finite Element Analysis

Aluminum foam is a lightweight material owing to the existence of a large number of internal pores. The compressive properties and deformation behavior of aluminum foam are considered to be directly affected by the shape and distribution of these pores. In this study, we performed image-based finite element (FE) analyses of aluminum foam using X-ray computed tomography (CT) images and investigated the possibility of predicting its deformation behavior by comparing the results of FE analyses with those of actual compressive tests. We found that it was possible to create an analytic model reflecting the three-dimensional (3D) pore structure using image-based modeling based on X-ray CT images. The stress distribution obtained from image-based FE analysis correctly indicates the layer where deformation first occurs as observed in actual compressive tests. Also, by calculating the mean stress of each plane perpendicular to the direction of compression based on the stress distribution obtained from image-based FE analysis, it was found that deformation begins in the layer containing the plane with maximum stress. It was thus possible to estimate the layer where deformation begins during the compression of aluminum foam.     

Amorphous Zr-Based Foams with Aligned,Elongated Pores

Interpenetrating phase composites are created by warm equal channel angular extrusion (ECAE) of blended powders of amorphous Zr_58.5Nb_2.8Cu_15.6Ni_12.8Al_10.3 (Vit106a) and a crystalline ductile metal (Cu, Ni, or W). Subsequent dissolution of the continuous metallic phase results in amorphous Vit106a foams with ~40 pct aligned, elongated pores. The extent of Vit106a powder densification in the composites improves with the strength of the crystalline metallic powder, from low for Cu to high for W, with a concomitant improvement in foam compressive strength, ductility, and energy absorption.     

Deformation of Pores in Viscoplastic Soil Material

Changes in soil pore volume and shape in response to internal and external mechanical stresses alter key soil hydrologic and transport properties. The extent of these changes is dependent on details of pore shape and size evolution. We present a model for quantifying rates of deformation and shape evolution of idealized spheroidal pores as functions of macroscopic stresses and soil rheological properties. Previous solutions for shrinkage of spherical pores embedded in a viscoplastic matrix under isotropic stress were extended to spheroidal pore shapes and biaxial stresses using Eshelby’s classical theory. Bulk soil behavior was obtained from upscaling of detailed single pore deformation. Results show that pore closure rates increase with decreasing initial aspect ratio (i.e., oblate pores close faster than spherical pores), and with higher deviatoric stress. Incomplete pore closure is attributed to soil hardening due to pore shape accommodation under biaxial stresses. The model provides a means for approximating pore deformation as input to predictive models for soil hydraulic properties.     

Detection and Influence of Shrinkage Pores and Nonmetallic Inclusions on Fatigue Life of Cast Aluminum Alloys

In the current study, test bars of cast aluminum alloys EN AC-AlSi8Cu3 and EN AC-AlSi7Mg0.3 were produced with a defined amounts of shrinkage pores and oxides. For this purpose, a permanent mold with heating and cooling devices for the generation of pores was constructed. The oxides were produced by contaminating the melt. The specimens and their corresponding defect distributions were examined and quantified by X-ray computer tomography (CT) and quantitative metallography, respectively. A special test algorithm for the simultaneous image analyses of pores and oxides was developed. Fatigue tests were conducted on the defective samples. It was found that the presence of shrinkage pores lowers the fatigue strength, and only few oxide inclusions were found to initiate fatigue cracks when shrinkage pores are present. The results show that the pore volume is not sufficient to characterize the influence of shrinkage pores on fatigue life. A parametric model for the calculation of fatigue life based on the pore parameters obtained from CT scans was implemented. The model accounts for the combined impact of pore location, size, and shape on fatigue life reduction.     

镁质熔剂性球团孔结构特性

 为了研究镁质熔剂性球团的孔特征,采用压汞法测量研究了碱度对镁质熔剂性球团孔结构的影响规律,利用多重分形理论分析了镁质熔剂性球团孔径分布的均匀性,并阐述了液相量和孔径与抗压强度之间的关系。结果表明,随着碱度的提高,镁质熔剂性球团的临界孔径先降低后增加,最可几孔径、平均孔径逐渐增大,孔径分布也越来越均匀,且主要以大孔为主;镁质熔剂性球团适宜的液相量有利于抗压强度的提高,可以弥补孔隙变大导致抗压强度降低的影响。