碳酸钙制备小孔径中等孔隙率类球形孔泡沫铝及其合金

与传统的Ca增黏与TiH2发泡的泡沫铝熔体发泡制备方法不同,CaCO3在铝熔体中可同时用作增黏剂和发泡剂.现有TiH2泡沫铝制备技术在制备小孔径类球形孔泡沫铝及合金方面存在困难,以轻质Ca-CO3颗粒为基础研制的新型泡沫铝增黏发泡剂,其热分解特性平缓,通过理论与实验确定了CaCO3在制备过程中的使用比例,分析了孔结构并讨论了CaCO3在铝熔体中的分解热力学问题,稳定制备出小孔径(0.4-1.1mm)、中等孔隙率(40-79%)的类球形孔泡沫铝及其合金.     

铝合金晶粒细化剂的研究现状与分析初探

文章在叙述铝合金熔体处理剂应用现状与细化机理的基础上，分析了稀土添加剂、Al-Ti-B中间合金细化剂以及Re-Al-TiB中间合金对铝合金铸态组织的影响，接着对复合添加剂稀土铝钛碳中间合金作了应用研究。结果表明：稀土铝钛碳的细化效果显著、抗衰减能力优越，能合理改善材料的强韧性，是一种高效能新型铝合金处理剂。     

铝合金熔体泡沫化过程中粘度的变化

用新型旋转扭矩探测仪对铝合金熔体增粘过程中的粘度进行了实时检测和控制,研究了熔体粘度的变化规律以及粘度对孔结构的影响规律.结果表明,在铝合金的增粘过程中粘度的变化与生长曲线类似;熔体的粘度过高使胞孔小、数量多;而粘度过低则相反.铝合金熔体泡沫化过程的最佳粘度值为27～28 mN·m,可以获得孔结构高度均匀、高比强的泡沫铝合金.     

细化、变质剂Al-Ti-C-Sr中间合金的制备及效果研究

采用二步法制备Al-Ti-C-Sr中间合金,预制AI-10Sr铝熔体温度850℃,用纯氩气精炼。采用自蔓延法预制Al-Ti-C铝液,氟钛酸钾和石墨粉加入熔体的温度为800℃-900℃,并在最终使熔体达到1200℃以上。合成Al-Ti-C-Sr中间合金是在Al-Ti-C熔体温度在800℃-900℃时加入AI-10Sr合金。再用制备好的Al-Ti-C-Sr中间合金对A356铝合金进行细化变质处理,具有细化和变质双重作用,效果明显。     

颗粒增强铝合金基泡沫铝材料压缩性能的研究

利用熔体发泡法制备了颗粒增强铝合金基闭孔泡沫铝,进行了准静态压缩和动态压缩实验,并且与铝合金基泡沫铝的相关性能进行了比较.研究了不同相对密度的泡沫铝准静态压缩和动态压缩性能.添加颗粒能增强基体合金性能,改善泡沫压缩效果.结果表明,在动态压缩和准静态压缩中,随着密度增加,颗粒增强基泡沫铝的平台应力和弹性模量逐渐增大;动态情形下的能量吸收能力要高于准静态情形下的能量吸收能力.向熔体中添加适当比例的粉煤灰颗粒可产生显著的基体增强效果,有效提高泡沫铝的压缩性能.     

泡沫SiC颗粒增强铝基复合材料的制备工艺和拉伸强度

介绍了一种新的泡沫金属材料－泡沫SiC颗粒增强铝基复合,泡沫的孔隙率为60％－85％。用TiH2作发泡剂,采用直接发泡工艺制备。由于复合材料熔体自身粘度较大,不需要采用任何增粘措施,发泡工艺简单,易于操作,该泡沫材料比普通泡沫铝或铝合金具有更高的抗拉、抗压强度。     

镀铜石墨与铝熔体的润湿性

为了改善石墨与铝的润湿性,通过化学镀使石墨颗粒表面形成完整致密的铜镀层,然后将8%(质量分数)的镀铜石墨粉通过熔体搅拌法加入到铝合金基体中制得金属基复合材料.采用改进的座滴法分别测定了铝熔体与石墨、镀铜石墨的接触角.同时,利用扫描电镜(SEM)对石墨颗粒增强铝基复合材料的微观形貌进行了检测.结果显示,铝熔体与镀铜石墨的接触角为27°,其界面具有良好的润湿性,镀铜石墨粉在铝合金基体中分布均匀.     

铝钛晶粒细化合金的离心压力铸造及其细化效果

研究了高钛晶粒细化中间合金的制造法以及它对铝合金的作用效果。试验结果表明，由于浇组时旋转离子压力作用，使铝钛合金细化剂中的Ａｌ３Ｔｉ颗粒明显减小，因而可使细化剂中允许的钛含量提高将近４倍，这样可大大减小细化剂在在被处理合金中的加入量。     

铝硅合金变质处理及去除超标镁锌的研究

系统研究了锶盐及其复合变质剂对铝硅合金的变质效果,以及几种处理方法对铝合金中杂质元素镁、锌的影响规律。所得主要结果是:锶盐可以使铝硅合金的硅相由针杆状变为长度尺寸在100μm以下的短杆状或弯曲的纤维状。锶盐变质剂存在着与锶变质相同的变质潜伏期现象,将锶盐与钠盐或磷盐复合变质能够消除这种现象。所研究的变质剂加入量小,提高合金的力学性能和使用性能;真空蒸发处理能够有效地降低铝合佥中的杂质锌量,向铝合金中吹入氟利昂与氮气的混合气体或加入六氯乙烷熔剂都能够有放地降低铝合金中的杂质镁量,根据铝合金的含镁量确定氟利昂的吹入量或六氮乙烷的加入量。     

Al-B-N中间合金对1070铝合金力学性能及导电性的影响

目的研究Al-B-N中间合金对1070铝合金力学性能和导电性的影响。方法向1070铝合金熔体中添加适量Al-B-N中间合金,借助其中的纳米AlN颗粒(AlN_P)强化铝基体,同时以AlB_2相去除铝中降低导电率的过渡族金属元素(如Zr,Cr,V等)。结果添加质量分数为2%的Al-B-N中间合金,1070铝合金强度由66MPa提高至85 MPa,导电率由60.14%IACS提升至62.12%IACS,较未添加之前分别提高了28.8%和3.2%,此时合金伸长率为35.8%。结论适量Al-B-N中间合金可以同时提高1070铝合金抗拉强度与导电率,实现协同强化。     

Effects of Sr-modification and melt cleanliness on melt hydrogen absorption of 319 aluminium alloy

The effect of Sr-modification on hydrogen content of commercial 319 aluminium alloy melts has been quantified, by using HYSCAN instrument at 685°C and 735°C. In addition, the effect of melt cleanliness on the hydrogen content of the melt has been studied. It has been found that the melt cleanliness has a significant effect on the reduction of hydrogen content of the melt. The hydrogen contents of Sr-modified cleaned melts were significantly lower (30-45%) than uncleaned melts (melts containing surface oxide layers) at both temperatures. Sr-modification had no marked effect on the hydrogen content of the melt at both temperatures, when measurements were carried out in a cleaned melt. Hydrogen content of strontium modified, uncleaned melts has been increased, particularly at 685°C. In order to study the melt hydrogen absorption susceptibility in Sr-modified alloys, the formation of different hydrogen containing compounds such as hydrides and hydroxide of modifiers and other alloying elements in Al-Si melts has been evaluated thermodynamically. It has been found that there is no hydrogen containing compound, which can form in aluminium melts, and if these compounds are introduced into the melt they will dissociated to release hydrogen.     

Fabrication of Al–TiC master composites and their dispersion in Al,Cu and Mg melts

Abstract

TiCpowders have been spontaneously infiltrated by molten Al with the aid of a K-Al-Fflux. The fluxdissolves the oxide film on the surface of molten Al, facilitating wetting between 'clean' Al and TiC particle surfaces, enabling liquid to be rapidly drawn into the network of TiC particles by capillary forces. The resulting master alloy was readily incorporated and dispersedinto molten Al, Cu, and Mg, indicative that the additive was readily wetted by all three molten metals and that the particles in the additive were not joined together by strong bonds. The use of a flux to facilitate cleaning of TiC, dissolution of Al in the meltand the avoidance of direct contactbetween TiC and melt surface oxides, all contribute to improved wetting. The slightly poorer quality of the particle distribution and the lowest yield in the Cu based alloy, suggest that wetting is worst in this system.     

Ca含量对SiC/Al泡沫复合材料性能和结构的影响

研究了SiC颗粒增强铝基（SiC/Al）复合材料中Ca含量对SiC分散性的影响以及Ca含量对注气法制备的SiC/Al泡沫复合材料的压缩性能和结构的影响。首先,制备不同Ca含量的SiC/Al复合材料,用来制备SiC/Al泡沫复合材料的基本材料,并对不同Ca含量的SiC/Al泡沫复合材料进行压缩实验;然后,利用OM、SEM和XRD研究了SiC/Al复合材料及泡沫结构中Ca含量对SiC分散性的影响。结果表明:Ca的加入会明显影响SiC/Al复合材料中SiC的分布,且存在Ca含量临界值。当Ca含量小于1.5wt%时,SiC在基体中分布较均匀;当Ca含量达到或超过1.5wt%时,熔体中生成一种富含Al、Ca和Si的金属间化合物Ca₂Al₄Si₃,且其体积分数和尺寸随Ca含量的提高而显著增大,SiC集聚在这些金属间化合物区域内及其边界上而影响SiC分布的均匀性。压缩实验表明,SiC/Al泡沫复合材料压缩应力-应变曲线的平台应力和抗压屈服强度随着Ca含量的增加有提高的趋势。相应的SiC/Al泡沫复合材料的胞壁厚度随着Ca含量的提高明显增加,这不仅与金属间化合物的形成提高了熔体黏度相关,更可能是与金属间化合物在熔体中尺寸随Ca含量提高而明显增大相关。      

Foaming behavior of Ti6Al4V particle-added aluminum powder compacts

The foaming behavior of 5 wt.% Ti6Al4V (Ti64) particle (30–200 μm)-added Al powder compacts was investigated in order to assess the particle-addition effects on the foaming behavior. Al compacts without particle addition were also prepared with the same method and foamed. The expansions of Ti64 particle-added compacts were measured to be relatively low at small particle sizes and increased with increasing particle size. At highest particle size range (160–200 μm), particle-added compacts showed expansion behavior similar to that of Al compacts without particle addition, but with lower expansion values. Expansions studies on 30–45 μm size Ti64-added compacts with varying weight percentages showed that the expansion behavior of the compacts became very similar to that of Al compact when the particle content was lower than 2 wt.%. However, Ti64 addition reduced the extent of drainage. Ti64 particles and TiAl₃ particles formed during foaming increased the apparent viscosity of the liquid foam and hence reduced the flow of liquid metal from cell walls to plateau borders. The reduced foamability in the compacts with the smaller size Ti64 addition was attributed to the relatively high viscosities, due to the higher cumulative surface area of the particles and higher rate of TiAl₃ formation between liquid Al and Ti64 particles.     

防锈闭孔泡沫Al-Mg-Re基合金的制备与性能

在熔体发泡法制备工艺基础上,引入合金化阻燃技术,制备了Al-Mg-Re基防锈闭孔泡沫铝合金.实验结果表明,熔体发泡前同时加入Mg、Ca和稀土制备的防锈闭孔泡沫Al-Mg-Re基合金孔结构均匀,由于Mg和稀土元素的双重作用,Al-Mg-Re基防锈闭孔泡沫铝合金具有优异的耐腐蚀性能.     

Effect of Decomposition Kinetics of Titanium Hydride on the Al Alloy Melt Foaming Process

The gas released from the titanium hydride decomposition is one of the key factors to influence the Al alloy melt foaming process.In this study,a set of decomposition kinetic equations of titanium hydride was acquired by separating its temperature programmed decomposition(TPD) spectrum,which was acquired by a special designed TPD apparatus with argon used as carrier gas and thermal conductivity cell as the detector.According to these equations,the decomposition and hydrogen release characteristics of titanium hydride at a fixed/elevated temperature are described quantitatively,which can be applied to forecast the Al alloy melt foaming process and furnish the theoretical basis for fabrication of three-dimensional complex shaped Al alloy foam.     

Effects of melt temperature and mold preheating temperature on the fluidity of Ca containing AZ31 alloys

The effects of melt temperature and mold preheating temperature on the fluidity of Ca containing AZ31 alloys were evaluated under various casting conditions. The flow lengths of AZ31-xCa alloy melt increased with increasing the melt temperature due to lower viscosity and longer time to fill the mold cavity. The increment of the flow lengths of AZ31-xCa alloy melt with increasing the mold preheating temperature was not large due to large diameter of circular cross section of mold cavity. The fluidity of AZ31-xCa alloy melts was affected more forcefully by melt temperature than by mold preheating temperature under casting conditions used in this study. Also, the flow lengths of AZ31-xCa alloy melt were affected by grain size of primary solid particles solidified during filling mold cavity and surface oxide film due to addition of Ca.     

Microstructure Control and Performance Evolution of Hypereutectic Al–20Mg2Si Alloy by Novel Al–Ca–Sb Masteralloy

Herein, the microstructure control and performance evolution of hypereutectic Al–20Mg₂Si alloy with the addition of novel Al–3.3Ca–10Sb master alloy are investigated. It is found that AlCa₁₁Sb₉ and CaSb₂ compounds are successfully synthesized through in situ melt reaction of masteralloy. With 0.45 wt% Al–3.3Ca–10Sb master alloy addition, primary Mg₂Si particles in hypereutectic Al–20Mg₂Si alloy are significantly refined from more than 150 μm to 10.7 μm, which are accompanied with the 3D morphologies changing from dendrites to octahedrons. After heat treatment, Brinell hardnesses of Al–20Mg₂Si alloys are remarkably improved to 112 HB. Furthermore, it is also found that the cooling rate of Al–3.3Ca–10Sb master alloys has certain influence on the refinement effect of Al–Mg₂Si alloys. The excellent complex modification of this master alloy on Al–20Mg₂Si alloy can be attributed to the existence of CaSb₂ particles as the heterogeneous nucleation sites of Mg₂Si particles and the inhibiting growth effect of residual Ca atoms adsorbed on the surface of Mg₂Si phase.     

Fabrication of Near Net Shape Metallic Foam via Plaster Mould

Fabrication characteristics are unstable in direct foaming method. Therefore, most of near net-shape metallic foams are produced, and investigated by powder metallurgy. Direct foaming method, however, has many benefits （i.e. reduce the unit cost of goods and fabrication process etc.） to fabrication of metallic foams. In this article, the fabrication characteristic of near net-shape metallic foams by direct foaming method was evaluated. Al and Plaster was used for base material and mould material respectively. Ca and TiH2 were added to molten Al as thickening and blowing agent for stable condition of bubbles. Thickening time was about 10 min with a stirring speed of 600 r/min. Foaming time was 30-120 s for evaluation of the optimum foaming condition. Amount of agent was selected by pre-experimental data. Porosity of near net-shape goods was measured by Archimedes method. On the other hand, it seems that increasing poring time and thickening agent make the poor porosity