泡沫铝三明治预制坯变形行为及复杂结构制备

利用粉末包套轧制法制备出泡沫铝三明治预制坯,通过室温与高温拉伸实验,研究了三明治预制坯的变形行为;采用冲压成形技术进行了三明治预制坯的成形试验,评价了其成形性能;在高温条件下进行了三明治预制坯的发泡实验,利用光学金相对泡沫铝三明治的微观结构进行了观察,并对孔隙特征进行了计算。结果显示,三明治预制坯既是温度敏感型材料也是速率敏感型材料,在450℃/0.001 s-1的条件下表现出较好的变形性能,其峰值应力与延伸率分别为22.1 MPa和23.8%;与室温条件相比,三明治预制坯在450℃条件下的热冲压成形精度更高,型面弧高达27.1 mm;高温发泡后制备出泡沫铝三明治弧面结构和曲面结构,证实了该工艺路线的可行性,其面板与芯板之间形成了冶金结合,且芯板的孔隙率达78%,平均孔径为3.5 mm,孔壁的微观组织为树枝状α铝和共晶相α+Si组成。     

发泡工艺对泡沫铝夹芯板孔结构及压缩性能的影响

采用包套轧制-粉末冶金发泡法制备了具有良好冶金结合界面的泡沫铝夹芯板,利用X射线衍射仪、扫描电镜、电子万能试验机等研究了发泡工艺对泡沫铝夹芯板宏观泡孔结构、微观芯层结构和压缩性能的影响.结果表明:发泡温度、发泡时间对泡孔结构起着决定性作用,而对微观组织几乎没有影响,发泡后芯层组织表现为在元素晶界处形成了Mg2 Si相、CuAl2相,620℃/15 min下发泡后得到的泡沫铝夹芯板具有最佳的综合力学性能.     

泡沫铝三明治结构的制备

采用粉末冶金发泡法制备了Ti/Al/Ti,Al/AlSi7／Al泡沫铝芯三明治结构，研究了泡沫铝制备工艺参数的影响，讨论了混粉、压力、温度等对发泡性能的影响，并对泡沫铝制备中的排液现象进行了探讨。     

三明治复合结构泡沫铝的制备及界面组织分析

采用冷压预制块(芯)与钢面板热压,然后发泡的工艺制备出了泡沫铝三明治复合结构(AFS).通过扫描电子显微镜(SEM)和元素线扫描对界面的微观组织及生成相成分进行了分析.试验结果和分析表明,热压过程中钢面板与芯部通过机械变形和元素扩散形成了牢固结合;发泡过程中,通过Fe、Al元素在界面的相向扩散,生成了FeAl3金属间化合物及(FeAl3+Al)共晶凝固组织,板芯间形成了良好的冶金结合界面.     

包套轧制粉末冶金法制备泡沫铝三明治板

以空气雾化的A1Si12合金粉、镁粉和氢化钛粉末为原料,采用包套轧制法成功制备出了泡沫铝三明治板材.利用300 dpi扫描仪、扫描电镜(SEM)和显微硬度仪等检测方法系统比较了复合轧制和包套轧制方法对制备前驱体的宏观形貌和界面结合及其泡孔结构的影响,结果表明:包套轧制可以有效阻止面板材料裂纹的扩展,获得完整的和致密度均匀的预制坯,并能实现面板芯材的有效结合,最终获得泡孔结构完整和均匀的泡沫铝三明治板.     

泡沫铝三明治预制坯变形失效及对发泡的影响

利用粉末包套轧制法制备出泡沫铝三明治预制坯,通过不同温度条件下的拉伸实验对三明治预制坯的变形性能进行了评价,采用光学金相显微镜(OM)与扫描电镜(SEM)对拉伸变形过程微观组织的演化以及断裂失效后的断口形貌进行了观察,通过高温发泡实验对不同拉伸变形的三明治预制坯的高温发泡行为进行了研究。结果显示,随着变形温度的升高,三明治预制坯的峰值应力呈现了快速降低的变化趋势,而延伸率则呈现了稳步上升的变化趋势,芯板的断口形貌由脆性断裂特征转变为韧性断裂特征。三明治预制坯中破碎的氢化钛颗粒是其变形失效的裂纹源,在变形过程中,裂纹将由此产生并向基体扩展延伸,同时,这些裂纹对三明治预制坯的发泡行为产生不利的影响,将形成孔隙不均匀的微观缺陷。     

压下率对泡沫铝夹层板制备的影响

以空气雾化的AlSi 12合金粉和TiH2粉末为原料,采用粉末包套轧制法成功制备出泡沫铝夹层板.通过对包套轧制进行了理论分析,结合SAYN-CG90数码相机、扫描电镜(SEM)和显微硬度仪等检测方法,系统研究了不同压下率对制备预制体的致密度和界面结合,以及泡沫铝夹层板泡孔结构的影响.结果表明:当压下率为70%的时候,可以获得表面平直、完整,粉体均匀、致密的预制坯,并且实现面板与芯层的有效结合,最终获得泡孔结构完整和均匀的泡沫铝三明治板.     

粉末冶金泡沫铝制备相关参数研究

在粉末冶金发泡法制备泡沫铝的基础上,研究发泡剂、发泡温度等参数对泡沫铝制备的影响。结果表明,Ti H2的分解峰值温度与铝的熔点十分接近,为640℃,其分解的气体体积是相同质量Ca CO3的30倍,是一种制备高孔隙泡沫铝较好的发泡剂;通过比较研究,发现铝发泡的合适温度为700~750℃,发泡时间宜选择在900 s左右;铝粉表面氧化膜对泡沫铝产生影响,氧化膜质量分数在9.8%左右时,孔隙率达到最大值77%,在氧化膜质量分数为8.2%左右时,孔径最不均匀。     

泡沫铝夹芯板的粉末冶金制备工艺

采用包套轧制法成功制备出了泡沫铝夹芯板,该工艺使泡沫铝夹芯板的面板与芯层达到了冶金结合.重点研究了发泡参数对泡孔生长的影响及泡孔的演变行为.结果表明:发泡温度、冷却速度与最终的发泡效果密切相关.发泡过程中,夹芯板芯层泡孔经历了气泡的形核、长大和合并等过程.     

TA1/Q235钢复合板累积叠轧焊界面特性

对TA1/Q235钢复合板累积叠轧焊进行了研究.研究结果表明:采用累积叠轧焊方法能够制备出结合性能较好的钛/碳钢复合板,其结合强度随着累积变形量与首道次变形量的增加而提高,叠轧过程中经磨床打磨与喷丸处理获得洁净、新鲜并具有一定加工硬化程度的结合界面,会促进复合板结合强度的提高.800℃以下热轧后,Q235钢的组织呈明显的条带状;而850℃以上热轧后,Q235钢条带状变形组织逐渐转化为等轴状,界面附近的Q235钢脱碳,出现明显的排列整齐且粗大的铁素体晶粒带.钛侧的组织主要有等轴α组织和魏氏α组织.综合考虑轧制温度对钛与Q235钢组织与界面结合性能的影响,累积叠轧温度应控制在800~850℃之间.     

Manufacturing of copper foams through accumulative roll bonding (ARB) process: structure and damping capacity behavior

Abstract

Closed cell copper foams have been produced through accumulative roll bonding (ARB) using calcium carbonate (CaCO₃) as blowing agent. Effects of temperature, time and number of rolling passes on the final porosity of the foam have been investigated. The foam with highest porosity has been achieved at 1100°C for soaking time of 3 min. Structure of composite has also been studied by optical and electron microscopy. The result shows that increasing the number of rolling passes reduces the size of powder and homogeneously distributes the particles within the copper substrate. By reducing the size of the particles, free surfaces of particles increase and the gas releasing sites in the foams are enhanced. Consequently, the final porosity of the composite is enhanced as well. The closed-pore foams have also been examined by modal analysis. It has been found that higher porosity of the final foams results in higher natural frequency and damping index.     

Fabrication of Al-3.7?Pct Si-0.18?Pct Mg Foam Strengthened by AlN Particle Dispersion and its Compressive Properties

Al-3.7 pct Si-0.18 pct Mg foams strengthened by AlN particle dispersion were prepared by a melt foaming method, and the effect of foaming temperature on the foaming behavior was investigated. Al-3.7 pct Si-0.18 pct Mg alloy containing AlN particles was prepared by noncompressive infiltration of Al powder compacts with molten Al alloy in nitrogen atmosphere, and it was foamed at different foaming temperatures ranging from 1023 to 1173 K. The porosity of prepared foam decreases and the pore structure becomes homogeneous with increasing foaming temperature. When the foaming temperature is higher than 1123 K, homogeneous pores are formed in the prepared ingot without using oxide particles and metallic calcium granules, which are usually used for stabilizing a foaming process. This stabilization of the foaming at high temperatures is possibly caused by Al₃Ti intermetallic compounds formed at high temperature and AlN particles. Compression tests for the prepared foams revealed that the absorbed energy per unit mass of prepared Al-3.7 pct Si-0.18 pct Mg foam is higher than those of aluminum foams strengthened by alloying or dispersion of reinforcements. It is remarkable that the oscillation in stress, which usually appears in strengthened aluminum foams, does not appear in the plateau stress region of the present Al-3.7 pct Si-0.18 pct Mg foam. The homogeneity in cell walls and pore morphology due to the stabilization of pore formation and growth by AlN and Al₃Ti particles is a possible cause of this smooth plateau stress region.     

Abnormal Ductility Increase of Commercial Purity Al During Accumulative Roll Bonding

In this paper, sheets of commercial purity Al were fabricated by the accumulative roll-bonding (ARB) method up to six cycles. To increase the shear deformation, no lubricant was used during the ARB processing and the samples were carried out for ARB processing without any preheat treatment. One interesting finding is that the ductility and strength both increased during the first several cycles of ARB processing. It is proposed that the initial rolling texture might play an important part in the subsequent ARB processing since the original Al sheets for ARB processing have not been subjected to any annealing. The microstructures of the specimens after each ARB cycle were investigated by transmission electron microscopy and correlated with the mechanical properties.     

利用选钛尾矿制备微晶泡沫玻璃及其性能研究

利用攀枝花选钛尾矿为主要原料,添加硼砂助熔剂经熔融、水淬、发泡、微晶、退火等系列工艺制备出微晶泡沫玻璃。研究了发泡剂种类、用量及稳泡剂用量、发泡时间、发泡温度、微晶化温度及时间等因素对微晶泡沫玻璃的表观密度、抗压强度和吸水率的影响。并通过SEM扫描分析制备的试样,内部出现充满连通且封闭的不规则气泡,孔壁较厚,体积膨胀明显的多孔状结构。研究结果表明:当发泡剂CaCO_3的添加量为2%,稳泡剂Na_3PO_4·12H_2O的添加量为5%时,在发泡温度840℃时发泡20 min,550℃微晶化处理90 min后可以制备孔径1.8~2.2 mm,表观密度1.31g/cm~3,抗压强度16.7 MPa,吸水率为11.3%的微晶泡沫玻璃。     

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。     

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。     

TiO2对合成渣中Fe2O3还原发泡过程的影响

研究了不同条件下TiO₂和Fe₂O₃在合成渣中被碳还原时的发泡过程.计算了该发泡过程的发泡系数、消泡系数、平均发泡寿命、发泡强度和消泡过程开始的时间.用熔渣发泡参数定量地讨论了温度、TiO₂加入量和初渣中TiC的含量对熔渣发泡过程的影响,发现当初渣中TiC的含量和TiO₂加入量较多时,在发泡时会产生二次发泡现象.     

Fabrication of Aluminum Foams with Small Pore Size by Melt Foaming Method

This article introduces an improvement to the fabrication of aluminum foams with small pore size by melt foaming method. Before added to the melt, the foaming agent (titanium hydride) was pretreated in two steps. It firstly went through the traditional pre-oxidation treatment, which delayed the decomposition of titanium hydride and made sure the dispersion stage was controllable. Then such pre-oxidized titanium hydride powder was mixed with copper powder in a planetary ball mill. This treatment can not only increase the number of foaming agent particles and make them easier to disperse in the melt, which helps to increase the number of pores, but also reduce the amount of hydrogen released in the foaming stage. Therefore, the pore size could be decreased. Using such a ball-milled foaming agent in melt foaming method, aluminum foams with small pore size (average size of 1.6 mm) were successfully fabricated.     

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。