用球化处理的粉末热压制备Cu-Al2O3复合材料

由机械合金化法(MA)制得纳米Al2O3颗粒弥散镶嵌于较软微米Cu颗粒表面的复合粉,利用球形化工艺改善所制得复合粉的形貌及工艺性能,然后通过热压法制备Cu-Al2O3复合材料.通过电导率测试、抗拉强度测试、密度测试、SEM形貌和断口分析、微区成分分析,研究了Al2O3质量分数分别为0%、0.5%、1.5%、2.5%时Cu-Al2O3复合材料的组织和性能.结果表明,随Al2O3质量分数增加,材料的抗拉强度总体增加,电导率、伸长率总体降低,Al2O3质量分数在1.5%时制得的复合材料具有较高的综合性能,此时σb=298MPa、δ=12.1%、电导率为88%IACS;质量分数继续增加会使纳米Al2O3颗粒发生局部团聚;在拉伸受力时复合材料发生延性断裂.     

热压反应合成Al_2O_3-Ho_2O_3/TiAl复合材料

利用Al-Ti-TiO2-Ho2O3体系原位反应合成了Ho掺杂Al2O3/TiAl复合材料。采用DTA结合XRD分析对体系反应过程进行了探讨。借助XRD、EDS和SEM等手段,对放热体系的物相组成及晶粒微观形貌进行了分析表征。结果表明:Al-Ti-TiO2-Ho2O3系原位合成的Al2O3/TiAl复合材料由TiAl、Ti3Al、Al2O3以及HoAl3相组成;Ho2O3的引入对基体相生成比例(TiAl:Ti3Al)有一定的调控作用,并使得基体晶粒和Al2O3晶粒均有所细化且逐渐分布均匀。力学性能测试表明:当Ho2O3的引入量为6%时,材料的抗弯强度达到最大值,约为593.5MPa;断裂韧度达到最大值,为8.74MPa.m1/2,具有可接受的力学性能。     

The mechanism of formation of TiB2 particulates prepared by In Situ reaction in molten aluminum

By making use of a novel technique in which TiB₂ particulates are fabricated by an in situ reaction in molten aluminum, we have successfully produced TiB₂/Al composites. In order to reveal the characteristic of the technique, the mechanism of formation of TiB₂ particulates obtained by this method is studied in this article. Both theoretical and experimental results have shown that the TiB₂ particulates are formed by a diffusion mechanism when the molar fraction of aluminum in the preform is higher than 43.5 pct. In this case, the TiB₂ particulates are generally spherical, and their mean size is less than 2.0 μm. On the contrary, the TiB₂ particulates are formed by a solution-precipitation mechanism when the fraction is lower than 43.5 pct. In this case, the TiB₂ particulates are multifaceted, and the size of most particulates lies between 3.0 and 6.0 μgm.     

粉末冶金法制备颗粒增强镁基复合材料的研究进展

概述了粉末冶金法制备颗粒增强镁基复合材料的研究进展, 介绍了颗粒增强镁基复合材料的常用基体和微米级、纳米级增强体。重点阐述了粉末冶金法制备颗粒增强镁基复合材料的工艺, 包括增强体预处理工艺、混合粉体成形工艺及烧结工艺。总结了粉末冶金制备工艺对复合材料组织与力学性能的影响规律, 包括增强体-基体界面结合情况的研究和颗粒增强体强化机制的探究。最后, 对粉末冶金法制备颗粒增强镁基复合材料的发展前景进行了展望, 并提出改进措施。     

Synergistic effects of wear and corrosion for Al2O3 particulate-reinforced 6061 aluminum matrix composites

Wear corrosion of alumina particulate-reinforced 6061 aluminum matrix composites in a 3.5 wt pct NaCl solution with a revised block-on-ring wear tester has been investigated. The studies involved the effects of applied load, rotational speed, and environments (dry air and 3.5 pct NaCl solution) on the wear rates of materials. Also various specimens with Al₂O₃ volume fractions of 0, 10, 15, and 20 pct were employed in this work. Electrochemical measurements and electron micrographic observations were conducted to clarify the micromechanisms of wear corrosion in such metal matrix composites. Experimental results indicated that the wear rate of monolithic 6061 Al in either dry wear or wear corrosion was reduced by adding alumina reinforcements. However, the effect of volume fraction on wear rate is only minor in dry wear, while it is significant in the case of wear corrosion. Wear-corrosion tests also showed that the corrosion potential shifted to the active side and the current density for an applied potential increased with the decrease of Al₂O₃ volume fraction in the materials and the increase in applied load and rotational speed. Although the incorporation of reinforcement in these aluminum matrix composites was deterimental to their corrosion resistance, the influence on wear corrosion was favorable.     

粉末热挤压法制备Mg2B2O5w/6061Al复合材料的组织和力学性能研究

采用粉末冶金法制备了含量分别为5%、10%、15%、20%(体积分数,下同)的硼酸镁(Mg2B2O5)晶须增强6061铝基复合材料,利用SEM和EPMA研究了复合材料的微观组织,并测定了其力学性能。结果表明:在复合材料制备过程中Mg2B2O5晶须发生了破碎和折断,Mg2B2O5多以晶须团聚体的形式存在,出现尺寸为10~25μm的颗粒状增强体;Mg2B2O5晶须沿挤压方向定向排列,并且定向排列性随晶须含量的增加而减弱;复合材料的抗拉强度随着晶须含量的增加先升高后降低,并在晶须含量为15%时达到最大值191MPa,较基体合金增加16.5%;复合材料的伸长率随晶须含量的增加逐渐下降,当晶须含量为20%时降至最低值6.3%。     

用氧化镧改性硫酸钛

硫酸钛掺杂La2O3后经高温焙烧制得一类稀土改性固体酸,用吸附吡啶的红外光谱表征其表面酸的性质,用合成丙酸丁酯的酸催化反应考察其催化活性。结果表明:固体酸中引入稀土元素,使得催化剂表面在保持Bronsted酸中心的同时,产生了新的Lewis酸中心;利用稀土的引入量不但可以调节固体酸表面B/L酸的比例,而且能提高固体酸中B酸的热稳定性。在催化合成丙酸丁酯化反应中,改性后的固体酸不但具有更好的酸催化活性,稀土含量少、反应后沉降快、易分离和回收、可重复使用多次,容易再生等优点,而且大大简化了反应的后处理工艺、产物无色、清亮透明。并获得催化剂制备优化条件为:镧含量5%,焙烧温度400℃。稀土改性后的固体酸是一种环境友好催化剂。     

Wettability of silicon carbide ceramic by Al2O3/Dy2O3 and Al2O3/Yb2O3 systems

Wettability is an important phenomenon in the liquid phase sintering of silicon carbide (SiC) ceramics. This work involved a study of the wetting of SiC ceramics by two oxide systems, Al₂O₃ /Dy₂O₃ and Al₂O₃ /Yb₂O₃, which have so far not been studied for application in the sintering of SiC ceramics. Five mixtures of each system were prepared, with different compositions close to their respective eutectic ones. Samples of the mixtures were pressed into cylindrical specimens, which were placed on a SiC plate and subjected to temperatures above their melting points using a graphite resistance furnace. The behavior of the melted mixtures on the SiC plate was observed by means of an imaging system using a CCD camera and the sessile drop method was employed to determine the contact angle, the parameter that measures the degree of wettability. The results of variation in the contact angle as a function of temperature were plotted in graphic form which showed that the curves displayed a fast decline and good spreading. All the samples of the two systems presented final contact angles of 40° to 10° indicating their good wetting on SiC in the argon atmosphere. The melted/solidified area and interface between SiC and melted/solidified phase were evaluated by scanning electron microscopy (SEM) and their crystalline phases were identified by X-ray diffraction (DRX). The DRX analysis showed that Al₂O₃ and RE₂O₃ reacted and formed the Dy₃Al₅O₁₂ (DyAg) and Yb₃Al₅O₁₂ (YbAg) phases. The results indicated that the two systems had a promising potential as additives for the sintering of SiC ceramics.     

内氧化法制备纳米Al2O3弥散铜复合材料的研究

以Cu-Al水雾化合金粉末为原料,通过内氧化方法制备了Al2O3弥散强化铜复合材料.结果表明:γ-Al2O3弥散相粒子在基体内均匀分布,尺寸约6nm,间距30～50nm.挤压态的弥散强化铜棒材(φ25mm)不经过任何中间热处理,直接冷拉拔得到φ1mm的铜丝,其丝材抗拉强度高达680MPa;挤压态棒材的电导率87％(IACS),软化温度850℃,材料的整体性能达到了国际先进水平.     

放电等离子烧结Ti_3SiC_2/金刚石复合材料的组织结构与磨削性能

采用Ti_3SiC_2粉体和不同粒度的金刚石颗粒为原料,通过放电等离子烧结制备Ti_3SiC_2结合剂/金刚石复合材料,研究金刚石粒度与烧结温度对该材料的物相组成、显微形貌以及磨削性能的影响。结果表明,烧结过程中,Ti_3SiC_2分解生成Si与TiC_x。当金刚石粒度较细(W20)时,金刚石表面的C元素与TiC_x充分反应,生成厚度约为1μm的TiC过渡层,Ti_3SiC_2结合剂/金刚石复合材料中存在许多孔隙,烧结温度为1 200~1 400℃时,该材料的主相是TiC_x,TiC和Ti_3SiC_2,当温度升高至1 500℃时,主相为TiC,含有少量Ti_3SiC_2;金刚石粒度较粗时(30/40,120/140目),在1 200℃温度下烧结的复合材料的主相均为Ti_3SiC_2与TiC_x,1 500℃下烧结时,含30/40目金刚石的复合材料主相为TiC和Ti5Si3,含少量Ti_3SiC_2,含120/140目金刚石的复合材料主相为TiC,含少量Ti_3SiC_2。用粒度为120/140目的金刚石颗粒制备的Ti_3SiC_2结合剂/金刚石复合材料的磨削性能最好,当烧结温度为1 400℃时,磨耗比达到6 857。     

Interfaces in MoSi2-SiC In Situ composites synthesized by melt processing

Interfaces between the primary β-SiC and the surrounding MoSi₂ matrix in melt-synthesized in situ composites have been investigated, with emphasis on the chemistry and crystallographic relationships developed during solidification. Primary SiC growth occurs with {002} and {111} facets, both of which are found to template the subsequent nucleation and epitaxial growth of the MoSi₂ matrix. Eight independent orientation relationships (ORs) were identified, involving the following combinations of planes: $$\begin{gathered} \left\{ {002} \right\}_{Sic} \parallel \left( {001} \right)_{MoSi_2 } \left( {3 rotational variants} \right), or \{ 101)_{MoSi_2 } \hfill \\ \left\{ {111} \right\}_{Sic} \parallel (001)_{MoSi_2 } , or \{ 100)_{MoSi_2 } \left( {2 rotational variants} \right),or \{ 101)_{MoSi_2 } \hfill \\ \end{gathered} $$ The interfacial relationships were rationalized using coincident site lattice arguments as well as energetic simulations based on the Grey-Bohr algorithm. The latter analysis suggests that the multiplicity of relationships arises from local effects associated with the size and shape of the adsorbate layers preceding the formation of the MoSi₂ nuclei. An amorphous carbon layer, 2- to 5-nm thick, was detected at all interfaces and some of the matrix grain boundaries. This interphase is believed to evolve by solid-state precipitation of C during postsolidification cooling and is, in principle, metastable. The C interphase enables easy debonding and thus may have important implications for the mechanical performance of materials involving SiC/MoSi₂ constituents.     

硫酸铝铵原位分解制备Al2O3颗粒增强铝基复合材料

向铸铝ADC12熔体中添加脱水后的硫酸铝铵,反应分解的Al2O3原位生成颗粒增强铝基复合材料,该方法既可节约成本,同时由NH4Al（SO4）2分解的SO3对熔体具有精炼作用．SEM观察表明,Al2O3颗粒在铝基体中细小弥散分布,形成球形、不团聚的增强体颗粒．与基材相比,该复合材料的耐磨性明显提高;拉伸试验显示,复合材料的抗拉强度和延伸率有所降低．     

Processing, microstructure, and mechanical properties of cast In-Situ Al(Mg, Ti)-Al2O3(TiO2) composite

In-situ particle-reinforced aluminum alloy-based cast composites have been synthesized by solidification of the slurry obtained by dispersion of externally added titanium dioxide (TiO₂) particles in molten aluminum at different processing temperatures. Alumina particles (Al₂O₃) form in situ through chemical reaction of TiO₂ particles with molten aluminum. Simultaneously, the chemical reaction also releases titanium, which dissolves into molten aluminum and results in the formation of intermetallic phase Ti(Al_1−x ,Fe _x )₃ during solidification. Increasing the processing temperature increases (1) the amount of elongated as well as blocky intermetallic phase Ti(Al_1−x ,Fe _x )₃, (2) the proportion of alumina particles in the reinforcing oxides, and (3) the porosity content in the resulting cast in-situ composite. The difference in particle content and porosity between the top and the bottom of the cast ingot increases with increasing processing temperature. The hardness of the cast in-situ composite is significantly more than that of the matrix alloy due to the presence of reinforcing particles, but the hardness is greatly impaired by the presence of porosity at the top of the cast ingot. The percent elongation of the cast in-situ composite decreases with increasing processing temperature possibly due to increasing porosity as well as an increasing amount of elongated intermetallic phase, which affects the percent elongation of the matrix alloy. The tensile and yield stresses of the cast in-situ composite decreases with increasing processing temperature again due to increasing porosity, which affects the ultimate tensile stress more than the yield stress. In the cast in-situ composite containing 3.31 ± 0.77 vol pct of porosity, the Brinell hardness is about 6 times its yield stress. The estimated yield stress of the cast in-situ composite at zero porosity as given by the linear least-squares fit appears to increase with particle content at a significantly higher rate than that predicted by the shear-lag model.     

Optical properties and irradiation resistance of novel high-entropy oxide glasses La2O3-TiO2-Nb2O5-WO3-M2O3(M=B/Ga/In)

A new class of high-entropy oxide glasses 20LaO_3/2-20TiO₂-20NbO_5/2-20WO₃-20MO_3/2(M=B/Ga/In)were designed and successfully fabricated by aerodynamic containerless processing.The results show that one can control the properties and increase the functionality of glass by changing the type of M.The Vicker’s hardness reaches the highest value of 6.45 GPa for glass M=B.The best thermal stability and the glass forming ability,measured using the gla...     

Evaluation of the wettability of liquid aluminum with ceramic particulates (SiC,TiC, AI2O3) by means of pressure infiltration

One of the major problems in the fabrication of aluminum-ceramic composites is the wettability of ceramic reinforcements by liquid aluminum. In this article, the wettability at the liquid metal/ ceramic particulates interface has been evaluated by means of an infiltration technique that permits a determination of the threshold pressure and the infiltration kinetics. The aim of the present article is to check the reliability of the experimental technique. The work was carried out on pure aluminum and A1₂O₃, SiC, and TiC particulates of average diametersD in the range 7.5 to 150 μm. An Al-1 wt pct Pb alloy was also used to investigate the effects of surface tension. All infiltrations were carried out in air. The results for the infiltrated heightvs applied pressure or time follow Darcy’s law. On the other hand, threshold pressures are proportional to 1/D (capillary law) and some deviations can be ascribed to differences in the shape of the particulates (especially TiC). More than 75 pct of the reduction in the threshold pressure promoted by 1 wt pct of lead can be related to the decrease in the surface tension of pure Al. The results indicate that effects due to changes in wetting should be very small, as expected when aluminum is covered with an oxide layer.     

原位制备细晶Si3N4-Si2N2O复相陶瓷

以Y2O3和Al2O3纳米陶瓷粉体作为烧结助剂，液相烧结非晶纳米Si3N4陶瓷粉体，制备Si3N4-Si2N2O复相陶瓷。Si2N2O相通过原位反应2Si3N4(s) 1．5O2(g)：3S12N2O(s) N2(g)生成。160012烧结，烧结体保温30min，Si2N2O体积分数达到52％，基本由细小均匀的球形晶粒构成。平均粒径尺寸210nm，相变过程中，个别颗粒异常长大，长径比达到1．5。保温时间对孔隙、密度和粒径产生重要影响：随着保温时间的延长，孔隙逐渐收缩减小，烧结体的致密度逐渐提高，晶粒逐渐长大，保温60min，孔隙几乎完全闭合，相对密度达到99．1％，平均粒径280nm。当保温时间达到90min时，相对密度增加并不明显，但平均粒径长大到360nm。     

碳纳米管和氧化铝颗粒协同增强铜基复合材料的制备与性能研究

本文首先利用碱式高锰酸钾对纯化后的CNTs进行改性处理,然后用分子水平法制得前驱体CNTs/Cu复合粉末,最后用内氧化方法,结合放电等离子烧结获得CNTs、Al_2O_3/Cu复合材料。结果表明:CNTs、Al_2O_3/Cu复合材料的维氏硬度(136)和抗拉强度(226 MPa)均优于两个增强相单独作用的铜基材料;材料的断后伸长率超过纯铜(40.1%),达到43.6%,表现出非常好的塑性;CNTs和Al_2O_3两个增强相对铜基材料导电率起到了协同增强作用,达到了1+12的效果。     

原位制备Fe(TiC)_p复合材料中增强相颗粒的组织遗传性及调控技术

以羰基Fe粉、Ti粉及C粉为原料,采用真空原位反应烧结法制备颗粒增强型Fe(TiC)_p复合材料。对微观组织的观察和元素分析发现,原料Ti粉对TiC增强颗粒的形貌和粒径具有较明显的遗传性。对这一组织遗传性,从反应热力学和扩散动力学方面给出解释,并基于此认识,设计原料Ti粉的球磨细化预处理工序。经预处理后原位反应烧结材料的致密度明显提升,并能够在铁基体中形成分散度更高、尺度更细小、且近球形的TiC增强颗粒,从而使复合材料的硬度从HV99.4提高到HV152.3,抗弯强度从550 MPa提高到935 MPa。