高体积分数SiCp/Al复合材料的微观组织与导热性能

选用两种粒径的SiC颗粒,采用挤压铸造方法制备了体积分数为70％的SiCp／LD11（Al-12％Si）复合材料,研究了材料的微观组织和导热性能．研究表明：复合材料组织均匀、致密;SiC—Al界面干净,而基体中的Si相分别存在从铝中直接析出和依附SiC颗粒表面生长这两种分布形态;复合材料导热性能优异,其导热率大于基体LD11铝合金的导热率．     

电子封装用SiCp/Al复合材料的组织与性能

本文选用粒径为20μm和60μm的SiC混合颗粒,采用挤压铸造方法制备了体积分数为70%的SiCp/LD11(Al-12%Si)复合材料.材料组织致密,颗粒分布均匀.复合材料具有低膨胀、高导热的特性和十分优异的力学性能,并且可以通过退火处理进一步降低其热膨胀系数.采用化学镀方法,在复合材料表面涂覆镍层,以其做为底座的二极管满足器件的可靠性测试要求.     

SiC颗粒增强铝基复合材料/半金属材料干摩擦磨损特性

采用自制的销盘式摩擦磨损试验机研究了三种颗粒增强铝基复合材料及灰铸铁(HT250)与半金属摩擦材料配副的干摩擦磨损性能。结果表明:在试验条件下,复合材料的耐磨性能高于灰铸铁(HT250),其中复合材料Al-10%Si/30%SiC(14μm)的平均磨损率小于灰铸铁的三分之一;复合材料的摩擦系数与HT250相当。而且从摩擦系数稳定性和摩擦系数达到最大值所需的时间来考察,复合材料的性能优于HT250。结果表明,颗粒增强铝基复合材料可以取代HT250,用于汽车刹车盘类摩阻件,使其使用寿命大幅度提高。     

片状Al2O3对Al2O3/FEP复合材料热导率的影响

通过混炼工艺制备了片状Al₂O₃填充聚全氟乙丙烯(FEP)复合材料,以颗粒状Al₂O₃为对比样品,研究了片状Al₂O₃形状和尺寸对 FEP基复合材料热导率的影响,利用SEM观察了FEP基复合材料的微观形貌。结果表明：在低填充量下,Al₂O₃颗粒在FEP基体中呈“海岛”状分布,没有形成连续的导热网链,但其热导率明显提高;复合材料拉伸强度与断裂伸长率随Al₂O₃含量的增加而减小;低填充量时复合材料热导率的提高主要来自Al₂O₃的微细片状结构,这种微细片状结构一方面提高了有效导热路径,另一方面增加了颗粒与基体之间接触面积,因此有利于热导率的提高。     

原位生成TiB2/ZA27复合材料的制备与性能

以Al熔液为载体,采用原位反应生成形状规则、尺寸细小的TiB₂颗粒相,再将TiB₂颗粒传递到ZA27合金中,形成TiB₂颗粒增强的ZA27复合材料。采用合理的熔炼工艺促进了TiB₂颗粒在基体中的均匀分布。实验结果显示,TiB₂颗粒在ZA27复合材料中,分布均匀,平均直径在3 μm以下。TiB₂颗粒的加入使得复合材料的晶粒明显细化,并随着TiB₂颗粒含量增加,复合材料的抗拉强度、硬度明显提高,2.1%TiB₂/ZA27复合材料与基体合金相比室温抗拉强度提高13%、布氏硬度提高21%,弹性模量也有所提高,在强度、硬度及弹性模量提高的同时,材料的塑性并未恶化,延伸率略有提高,另外,材料的热膨胀系数随着TiB₂颗粒的加入有所降低。     

原位反应法制备Al/Al3Ti复合材料组织和性能

本研究采用一种新型的原位反应工艺,使TiO₂粉剂与纯铝熔体反应,生成Al3Ti颗粒,然后采用搅拌铸造法制备Al/Al₃Ti复合材料。生成的Al₃Ti颗粒尺寸细小,为2～3μm,而且分布均匀,与基体结合好。当TiO₂加入量为纯铝基体的30wt%、反应温度为920℃时,复合材料的抗拉强度比纯铝基体提高71.5%,硬度提高134%,而延伸率较纯铝稍有下降。     

离心铸造原位生成初生Ti（AlSi）2颗粒增强Al-16Si-6Ti复合材料筒状零件的组织与性能

采用离心铸造方法制备了Al-16Si-6Ti复合材料筒状零件,使用SEM,EDS及OM观察分析了复合材料中的微观组织,使用Image Tool测算了铸件中初生颗粒的体积分数,测试了复合材料的硬度及耐磨性能。结果表明:离心铸造Al-16Si-6Ti筒状零件沿半径方向形成了具有大量初生Ti(AlSi)2颗粒的外层增强层组织,无初生颗粒的铝基体中间层组织以及含有少量初生Si颗粒的内层组织。从外壁到内壁,铸件的硬度及初生颗粒的体积分数均呈现先由高到低,然后小幅上升的变化规律。铸件外层组织具有最好的耐磨性能。在离心场中,初生Ti(AlSi)2向铸件外侧偏移、聚集,形成了高体积分数的初晶Ti(AlSi)2颗粒增强铸件外层的Al基复合材料。     

离心铸造原位生成初生Ti(AlSi)_2颗粒增强Al-16Si-6Ti复合材料筒状零件的组织与性能EI北大核心CSCD

采用离心铸造方法制备了Al-16Si-6Ti复合材料筒状零件,使用SEM,EDS及OM观察分析了复合材料中的微观组织,使用Image Tool测算了铸件中初生颗粒的体积分数,测试了复合材料的硬度及耐磨性能。结果表明:离心铸造Al-16Si-6Ti筒状零件沿半径方向形成了具有大量初生Ti(AlSi)2颗粒的外层增强层组织,无初生颗粒的铝基体中间层组织以及含有少量初生Si颗粒的内层组织。从外壁到内壁,铸件的硬度及初生颗粒的体积分数均呈现先由高到低,然后小幅上升的变化规律。铸件外层组织具有最好的耐磨性能。在离心场中,初生Ti(AlSi)2向铸件外侧偏移、聚集,形成了高体积分数的初晶Ti(AlSi)2颗粒增强铸件外层的Al基复合材料。     

环保型电子封装用Sip/Al复合材料性能研究

为研究电子封装用Sip/Al复合材料热物理及力学性能,利用挤压铸造方法制备了体积分数为65%的Sip/LD11(Al-12%Si)可回收环保型复合材料.采用TEM观察、膨胀仪、激光导热综合测试仪以及万能电子拉伸试验机等设备及技术对复合材料进行研究.结果表明:Sip/LD11复合材料组织致密,材料中未观察到孔洞和缺陷;20～50℃时复合材料的热膨胀系数为8.1×10-6/℃,并随着温度的升高而增加,退火处理能够降低复合材料的热膨胀系数;Sip/LD11复合材料铸造状态和热处理状态的热导率分别为132.9、160.1 W/m·℃,复合材料的弯曲强度和比模量较高;可以采用化学镀方法在复合材料表面涂覆Ni层,镀层结合强度良好,是一种优异的电子封装用复合材料.     

Al2O3颗粒增强纯铝基复合材料的研究

本文探讨了用粉末冶金法,采用常规的冶金加工设备和工艺,制造Al₂O₃颗粒增强纯铝基复合材料的可行性。研究了不同Al₂O₃体积含量复合材料的显微组织及力学性能。初步试验了二次热挤压变形对颗粒分布和对基体强化的影响。结果表明,Al₂O₃颗粒与纯铝粉混合,加压烧结制备的复合材料,组织致密,颗粒分布均匀,随Al₂O₃含量增加,复合材料强度、硬度及弹性模量大大提高,Al₂O₃含量小于10%时,塑性不降低。二次热挤压有助于提高颗粒分布的均匀性;并使基体显著强化。     

Effect of SiC Particulates on the Microstructure of Al-6Ti-6Nb Matrix Composites Fabricated by Mechanical Alloying Technique

Millimeter sized SiC (m-SiCp) and nanometer sized SiC (n-SiCp) particulates reinforced Al-6Ti-6Nb matrix composites were prepared by mechanical alloying (MA) and later hot-press sintering. Their microstructure was investigated to know the influence of the incorporated SiC particles. The secondary Al3Ti, AlNb2 intermetallics particle size, the Al matrix grain size and their submicrostructure are strongly affected, and they are correlated with the thermal stability of the composites.     

Effect of the Presence of SiCp on Dendritic Coherency of Al-Si-Based Alloys During Solidification

In order to explore the effect of the presence of SiC particles on dendritic coherency during solidification of Al-Si based metallic alloys, a factorial fractional two levels experimental design was implemented to allow an identification of the main effects of the particle content, silicon content, grain refinement, and cooling rate on the solid fraction at coherency. This solidification parameter was determined for Al-3wt%Si and Al-7%Si alloys, and Al-3%Si/SiCp and Al-7%Si/SiCp metal matrix composites. The cooling process during solidification was monitored by performing cooling curve measurements at two radial locations within samples poured into cylindrical molds at two cooling rates. The experimental cooling curves were numerically processed by the Fourier thermal analysis method to know the evolution of solid fraction as a function of time. The effect of grain size was included using samples with or without grain size refinement. The grain refinement was obtained by adding predetermined quantities of TiAlB master alloy. It was found that presence of SiC particles affects the coherency point of the metal matrix composites increasing the solid fraction at coherency. However this effect is relatively small when compared to the effect of grain refinement, cooling rate, and Si content on dendritic coherency of experimental probes.     

高比例SiC_p/Al复合材料的有效热导率模型

有效热导率是铝基复合材料在电子封装、热控方面应用的重要性能指标.结合复合材料广义自洽微观力学模型,并在Maxwell理论的基础上,初步建立了适合高体积分数SiCp/Al复合材料的有效热导率预测模型.模型不仅考虑了颗粒与颗粒、颗粒与基体间的界面效应,而且在一定程度上也考虑了增强体颗粒的形状.其理论计算结果与实测值吻合较好.     

FABRICATION OF SiCp-AI COMPOSITE MATERIALS

Liquid phase fabrication methods for aluminum matrix composites reinforced with SiC whiskers, or SiC particles have been investigated and the mechanical properties of fabricated composites have been evaluated. Three kinds of liquid phase fabrication methods; hot extrusion, hot pressing and pressure infiltration, were studied. Commercial SiC whiskers and SiC powders of alpha type and beta type were used as the reinforcements for an aluminum matrix. Among the fabrication methods investigated, the best results were achieved by the pressure infiltration. The mechanical properties and the wear resistance of the fabricated composites were measured. The SiC whisker reinforced aluminum matrix composites have high strength, so that they can be used as high specific strength materials. The SiC particulate reinforced aluminum matrix composites are not strong as the SiC whisker reinforced composites. However, the SiC particulate reinforced aluminum matrix composites have a good potential for use as wear resistant material. The hardening effect of beta type particles on the aluminum matrix was larger than that of alpha type particles.     

连续分布界面相对SiCp/Al复合材料热导率影响的数值模拟

采用有限元方法对SiCp/Al复合材料的导热性能进行了数值模拟, 建立了含界面相颗粒增强铝基复合材料测试模型, 研究了不同界面相种类、厚度对复合材料热导率的影响。结果表明: 当界面相与SiC/Al结合理想时, 且界面相在颗粒表面呈连续分布时, 复合材料热导率随着界面层热导率的增加而增大, 但增加的幅度由快变慢; 复合材料热导率随界面层厚度的变化取决于界面层厚度t与颗粒粒径a的比值, 当t/a很小或t/a较大时, 热导率随界面层厚度的变化很小, 当t/a较小时, 热导率随界面层厚度的变化则与界面层热导率有关。     

放电等离子烧结制备Diamond/Al复合材料

采用放电等离子烧结法（SPS）制备了Diamond/Al复合材料,研究了金刚石粒径、成分配比、工艺参数等对复合材料的导热性能的影响。结果表明,SPS可以得到导热性能较好的Diamond/Al复合材料,致密度是影响该材料导热性能的最重要因素。在实验确定的金刚石体积分数50%,金刚石粒径70 μm,温度550℃、压力30 MPa的工艺条件下,所制备的材料致密度较高,热导率为182 W/(m·K),比相同条件下纯铝粉烧结体的热导率提高了34.8%,表明金刚石的添加对烧结铝基材料导热性能有明显的改善作用。      

SiCp/Al复合材料的SPS烧结及热物理性能研究

采用纯粉末, 通过SPS烧结制备了组织均匀、致密且体积分数高的SiCp/Al电子封装材料. 通过对SPS烧结现象的研究, 认为该复合材料的SPS烧结过程属于反应性烧结, 大部分收缩在极短时间内完成; 另外对SiC体积分数和SiC颗粒尺寸对热导率、热膨胀系数的影响进行了研究, 发现SiC体积分数越高, 复合材料的热导率和热膨胀系数越低; SiC颗粒粒径增大, 复合材料的热导率增高, 而热膨胀系数减小.     

Effect of coupling agents on the thermal conductivity of aluminum particle/epoxy resin composites

In this study, four kinds of coupling agents (CA), i.e., γ-aminopropyltriethoxysilane (KH-550), (3-glycidyloxypropyl)trimethoxysilane (KH-560), isopropyl tri(di(2-ethylhexyl)pyrophosphate)titanate (NDZ-201), isopropyl tri(di(2-ethylhexyl)phosphate)titanate (NDZ-102), were used to investigate their influences on the thermal conductivity and morphology of aluminum (Al) particle reinforced epoxy composite. The results indicate that the thermal conductivity of the composites increases with increasing Al particles concentration up to 48 vol.%; the surface modification of Al particles has an appreciable effect on the thermal conductivity. The thermal conductivities of the composite containing 48 vol.% Al particles treated with the KH-550, KH-560, NDZ-201, and NDZ-102 couplers, are 1.29, 1.48, 1.27, and 1.36 W/m K, respectively, corresponding to 1.03 W/m K of that without surface treatment. Furthermore, the concentration of CA has an influence on the thermal conductivity of the composites.