颗粒增强金属基复合材料中界面附近位移场测量的探索

本文采用数字散斑相关法对高能超声法制备的颗粒增强金属基复合材料在拉伸变形过程中颗粒与基体的界面处的位移进行了测量与分析，。实验结果表明，界面处所发生的位移变化要大于颗粒和基体内部所发生的位移，说明在颗粒与基体合金的界面处存在着导致应变集中的缺陷，从而导致了颗粒增强金属基复合材料失效过程中常常出现颗粒与基体在界面处脱粘的损伤形式。     

界面结构对纳米镶嵌颗粒熔化行为的影响

分别研究了具有两种界面结构的Ｉｎ和Ｐｂ纳米镶嵌颗粒（Ａｌ基体）的熔化行为，发现与Ａｌ基体具有附生取向关系的Ｉｎ和Ｐｂ纳米颗粒的熔点升高，而与Ａｌ基体随机取向的Ｉｎ和Ｐｂ纳米颗粒的熔点则降低，说明界面结构决定了纳米颗粒熔点的升降。     

扫描声学显微镜对压电复合材料结构的研究

对以聚氯乙烯为基体、压电陶瓷粉为增强颗粒的压电复合材料的颗粒分布用扫描声学显微镜进行了显微成像研究。结果表明，在垂直注入增强颗粒的情况下，由于重力的作用，悬浮颗粒的浓度沿垂直方向进行再分布，Ｎｍａｘ与颗粒大小和聚合基体的力学性能有关。     

颗粒增强金属基复合材料凝固理论研究进展

分析了颗粒增强金属基复合材料凝固过程的特点，分析评述了复合材料凝固过程中增强颗粒对基体金属凝固特性的影响和增强颗粒与基体金属固／液界面之间相互作用这两个方面的研究进展。     

二氧化锡颗粒增强银基复合材料的电阻率

根据复合材料的传导理论ｇ－ＭｅＯ系金属基复合材料电阻率的计算模型，并与Ａｇ－Ｓ的实验结果进行了对比。结果分析表明，颗粒增强金属基复合材料的电阻率不仅与基体和颗粒材料的电阻率及颗粒的体积分数有关，还与颗粒粒度及在基体中的分布状态有关。     

激光增材制造镍基复合材料界面连接机制与断裂行为

基于颗粒增强镍基复合材料优异的结构/功能特性，在航空航天、核电军工和电子电工等领域有着广泛的应用前景。本文选用机械球磨混粉+激光选区熔化方法 (SLM)制备了碳化钨(WC)颗粒增强IN718复合材料(WC/IN718)，对复合材料内部异质界面连接机制、强化机制和断裂行为进行了分析。研究结果表明：随着WC颗粒含量的增加(0wt%～20wt%)，试件成形良好，WC颗粒均匀分布在基体内部，异质界面处无缺陷产生，界面处产生了贫碳的W₂C层和碳化物层，基体合金主要呈柱状晶生长。由于熔池内部能量密度分布不同，低温位置WC颗粒的断裂方式为先形成界面反应层后由热应力引起断裂，高温位置WC颗粒优先发生断裂，断裂成小尺寸颗粒，后与熔化的基体合金形成界面反应层，弥散分布在基体内部。随着WC颗粒含量的增加，复合材料的强度呈现升高的趋势，而断裂韧性降低，抗拉强度最高可达1 280 MPa，强化机制主要为载荷传递强化，断裂机制为WC颗粒的脆性断裂和基体合金的韧性断裂。     

纳米SiC颗粒对Al2O3基体中ZrO2约束稳定的影响

采用热压的方法制备了纳米SiC颗粒复合的Al2O3-ZrO2陶瓷材料，研究了纳米SiC颗粒对样品烧结性能以及对Al2O3基体中ZrO2约束稳定的影响。结果表明，纳米SiC颗粒的加入影响样品的烧结性能。处于晶界的纳米SiC颗粒降低了基体材料对ZrO2颗粒的约束，不利于四方相ZrO2在室温下的保留。     

无机矿物填料表面纳米化修饰及性能表征

采用化学方法对无机矿物填料表面进行包覆改性，制备出具有表面纳米化结构的复合矿物颗粒，有效地改善了原有颗粒的表面形貌，提高了比表面积，通过搅拌磨湿法研磨，讨论了包覆颗粒与基体的结合方式，初步证明了包覆颗粒与基体的结合方式为化学吸附而非物理吸附，两者结合牢固，包覆层不易脱落，包覆矿物颗粒在聚丙烯（PP）中填充，其复合材料的力学性能有较大的改善。     

对辊快速凝固制备颗粒增强铝基复合材料的新途径

为了制备基体晶粒细小，增强颗粒分布均匀且与基体结合良好，界面上无明显反应产物的颗粒增强铝基复合材料，在铝及铝合金双辊快速凝固技术研究的基础上，提出了同步喷射增强颗粒和结合熔体接触反应法的两种双脱快速凝固制备方法，介绍这两种方法制备颗粒增强铝基复事材料的思路，阐述了制备了复合材料的潜在特点。     

双辊快速凝固制备颗粒增强铝基复合材料的新途径

为了制备基体晶粒细小、增强颗粒分布均匀且与基体结合良好、界面上无明显反应产物的颗粒增强铝基复合材料，在铝及铝合金双辊快速凝固技术研究的基础上，提出了同步喷射增强颗粒和结合熔体接触反应法的两种双辊快速凝固制备方法，介绍了这两种方法制备颗粒增强铝基复合材料的思路，阐述了制备的复合材料的潜在特点。     

Failures analysis of particle reinforced metal matrix composites by microstructure based models

This paper discusses the methodology of microstructure based elastic–plastic finite element analysis of particle reinforced metal matrix composites. This model is used to predict the failure of two dimensional microstructure models under tensile loading conditions. A literature survey indicates that the major failure mechanism of particle reinforced metal matrix composites such as particle fracture, interfaces decohesion and matrix yielding is mainly dominated by the distribution of particles in the matrix. Hence, analyses were carried out on the microstructure of random and clustered particles to determine its effect on strength and failure mechanisms. The finite element analysis models were generated in ANSYS, using scanning electron microscope images. The percentage of major failures and stress–strain responses were predicted numerically for each microstructure. It is evident from the analysis that the clustering nature of particles in the matrix dominates the failure modes of particle reinforced metal matrix composites.     

颗粒形状对复合材料单轴棘轮行为及其细观塑性变形特征的影响

在细观有限元模型基础上 , 利用 ABAQUS有限元程序对具有不同颗粒形状(球形、 立方体、 短棱柱和短圆柱)的 SiC P/ 6061Al 合金复合材料的单调拉伸行为和单轴棘轮行为进行数值模拟 , 讨论颗粒形状对复合材料棘轮行为的影响。 结果表明: 颗粒形状对复合材料的弹性模量、 单拉行为和单轴棘轮行为均有较大影响。 在所讨论的几种颗粒形状中 , 球形颗粒的增强效果最弱 , 抵抗棘轮变形的能力最差 ; 不同短棱柱颗粒的增强效果与其拥有的棱边数有关 , 即五棱柱颗粒的增强效果最好 , 然后随棱边数的增加逐渐下降 , 最后接近于短圆柱形颗粒。通过有限元分析结果讨论了不同颗粒形状下基体的细观塑性变形特征及其演化规律 , 这些结果有助于分析该类复合材料损伤和失效机制。      

Interfacial energy issues in ceramic particulate reinforced metal matrix composites

One major scientific issue that needs to be resolved and understood in order to design ceramic particle reinforced metal matrix composites is the interfacial energy state between the matrix and the reinforcement. Solid-solid interfacial energy between the particle and the matrix effects the final interface characteristics and also significantly influences the particle redistribution due to its effect on particle pushing engulfment by the melt interface. The paper analyses the physics behind the particle pushing and engulfment by the solidifying interface considering models utilizing interfacial force as energy difference between the particle in the solid and particle in the liquid melt. Various methods of evaluating solid-solid interfacial energy have been discussed. Velocity of melt interface movement at which the particles are engulfed by the matrix referred to as critical velocity of the system under given conditions has been shown to be directly related to the interfacial energy. Critical appraisal of experiments to determine the critical velocity have been presented for aluminium matrix dispersed with zirconia particles. Advantages of carrying out experiments under μg environment have been pointed out.     

颗粒尺寸对B4C增强铝基中子吸收材料界面反应与力学性能的影响

采用粉末冶金真空热压法制备了B₄C质量分数为31%、平均颗粒尺寸分别为6.5 μm、9.3 μm、17.3 μm、28 μm、39.5 μm的纯Al和6061Al基体的复合材料。对复合材料进行微观结构和力学性能检测,结果表明:所有复合材料的B₄C颗粒在基体中都均匀分布,且致密度都达到99%以上;对于纯Al基复合材料,随着颗粒尺寸增加,其致密度和塑性逐渐增加,强度逐渐下降;对于6061Al基复合材料,致密度随着颗粒尺寸的增加稍有降低,其强度和塑性受颗粒尺寸和热压温度共同影响,当热压温度610℃时,界面反应严重,随B₄C颗粒尺寸增加,强度先下降后上升,塑性先上升后下降;当热压温度580℃时,界面反应轻微,复合材料强度逐渐下降,塑性逐渐上升。颗粒尺寸、界面反应和基体材料等均影响B₄C增强铝基复合材料的力学性能。      

Effect of microstructure on Young’s modulus of extruded Al–SiC composites studied by resonant ultrasound spectroscopy

In this work, an attempt was made to correlate the Young’s modulus of SiC particle reinforced aluminum alloy composites, measured by resonant ultrasound method, to reinforcement spatial distribution. Composites were fabricated by extrusion of billets that were previously formed using cold pressing blend of matrix alloy powders and ceramic particles. It has been shown that more aggregated microstructures were generated with an increase in ceramic volume fraction (to 20%) and the matrix alloy powder mean particle size from 40 to 180 μm as well as with a decrease in the reinforcement particle size (3–14 μm). At the same time, ultrasonic wave velocity as well as Young’s modulus diminish with a decrease in SiC content and its particle size, and with increase in matrix alloy particle size. The analysis showed that it could be partly attributed to the higher amount of residual porosity in agglomerated structures. An addition decrease of elastic characteristics was attributed to the increasing influence of mechanically imperfect contacts that formed between ceramic particles in the more aggregated microstructures.     

Effects of soft hemispherical particle on local surface stress of hard matrix

Abstract

Finite element analysis was performed to investigate the stresses within and around a soft hemispherical particle located on the surface of a hard matrix under a remote external tensile load. The purpose was to understand the effects of neodymium rich particles on the fatigue properties of Ti-55 alloy. Three case studies were considered. First both particle and matrix were perfect, second a crack existed within the particle, and third a crack was located in the matrix adjacent to the particle. Numerical results show that soft particles cause stress concentration in regions of the matrix adjacent to the particle, but that such stress concentrations are much weaker than those associated with a cavity. A crack within the particle increases the stress concentration in the matrix only a little when the crack is far from the interface. However, a crack in the matrix significantly increases local stress in the particle.     

表面活性剂浓度对乳胶基质平均粒径的影响和机理分析

乳胶基质内相液滴的平均粒径大小直接反映了可燃剂和氧化剂的混合均匀程度,是影响乳化炸药爆炸性能和稳定性能的重要因素。主要研究了油相中表面活性剂浓度对乳胶基质内相液滴平均粒径的影响。使用5种含有不同表面活性剂浓度的外相材料制备乳胶基质,并且使用激光粒度仪测试了所有样品的平均粒径。实验结果表明:油相材料中表面活性剂的浓度越大,则制备出的乳胶基质平均粒径越小。然后通过表面张力的理论分析和外相动力粘度的实验测试,进而分析出增加表面活性剂降低乳胶基质的平均粒径的机理:表面活性剂的增加导致了外相材料的动力粘度的增大,进而使乳胶基质平均粒径变小,和表面张力无关。     

Effect of friction stir processing and hybrid reinforcements on copper

In this research, a copper based surface composite was fabricated through dispersing hybrid composite particles onto its surface through friction stir processing (FSP) technique. Optical micrographs and scanning electron microscopy images indicates finer refinement of grains and particles dispersion into matrix along with its bonding and particle separation. As per the outcomes of microhardness analysis, hardness of the developed surface composite shows increment with increase in dispersion of volume fraction of hybrid particles. Strength of the developed copper surface composite exhibited a positive trend with introduction of hybrid reinforcement particle onto the surface of the composite but yet again ductility reduced. Wear resistance of the composite increased with reinforcement addition and the same was supported through worn out surface morphology. Fluctuations in friction coefficient value reduced with increase in particles, as for the presence in BN particles while the average frictional coefficient value was observed increasing. A reduction in corrosion rate was observed with increase in reinforcement particle dispersion onto copper matrix through FSP.     

Failure of cemented granular materials under simple compression: experiments and numerical simulations

We investigate the strength and failure properties of a model cemented granular material under simple compressive deformation. The particles are lightweight expanded clay aggregate beads coated by a controlled volume fraction of silicone. The beads are mixed with a joint seal paste (the matrix) and molded to obtain dense cemented granular samples of cylindrical shape. Several samples are prepared for different volume fractions of the matrix, controlling the porosity, and silicone coating upon which depends the effective particle–matrix adhesion. Interestingly, the compressive strength is found to be an affine function of the product of the matrix volume fraction and effective particle–matrix adhesion. On the other hand, it is shown that particle damage occurs beyond a critical value of the contact debonding energy. The experiments suggest three regimes of crack propagation corresponding to no particle damage, particle abrasion and particle fragmentation, respectively, depending on the matrix volume fraction and effective particle–matrix adhesion. We also use a sub-particle lattice discretization method to simulate cemented granular materials in two dimensions. The numerical results for crack regimes and the compressive strength are in excellent agreement with the experiments.     

Heterogeneous and homogenized models for predicting the indentation response of particle reinforced metal matrix composites

In this study, three-dimensional heterogeneous and homogenized finite element models are used to predict the indentation response of particle reinforced metal matrix composites (PRMMCs). The matrix is assumed to have elasto-plastic behavior whereas the particles (uniform in size and spherical in shape) are assumed to be harder than the matrix, and possess linear elastic behavior. The particles (25 % by volume) are randomly distributed in the metal matrix. Two modeling approaches are used. In the first approach, the PRMMC is fully replaced by an equivalent homogenous material, and its material properties are obtained through homogenization using representative volume element approach under periodic boundary conditions. In second approach, a small cubical volume under the indenter is modeled as heterogeneous material with randomly distributed particles, whereas the remaining domain is assigned equivalent material properties obtained through homogenization. The elastic material properties obtained through simulations are found within Hashin–Shtrikman bounds. A suitable size cubical volume consisting of heterogeneities under the indenter is established by considering different cubical volumes so as to capture the actual indentation response. The simulations are also carried out for different particle sizes to establish a suitable particle size. These simulations show that the second modeling approach yields harder indentation response as compared to first modeling approach due to the local particle concentration under the indenter.