碳化硅颗粒增强铝基复合材料的微屈服行为研究

采用无压渗透法制备碳化硅颗粒增强铝基复合材料，探讨了基体材料、增强相尺寸、增强相体积分数、热处理工艺等对其微屈服行为的影响。结果表明：在其它条件不变的情况下，随着增强体颗粒尺寸的减小、增强体体积分数的增大，复合材料的微屈服抗力逐渐增大，有较好的微屈服行为。通过选择适当的基体材料、合理的热处理工艺来提高基体强度，可使复合材料的微屈服抗力增大。     

颗粒尺寸对SiCp/Mg复合材料热膨胀性能的影响

设计并采用真空气压浸渗法制备了不同颗粒尺寸的高体积分数SiCp/AZ91D镁基复合材料,研究了颗粒尺寸对镁基复合材料热膨胀性能的影响.结果表明,改变颗粒尺寸是调节镁基复合材料热膨胀性能的一种非常有效的手段.相同体积分数复合材料的热膨胀系数随颗粒尺寸的减小而逐渐降低,不同体积分数的SiCp复合材料的热膨胀系数与复合材料的界面面积成反比关系;减小颗粒尺寸与提高颗粒体积分数一样,能有效降低复合材料的热膨胀系数;颗粒尺寸对镁基复合材料热膨胀性能的作用机制主要是通过复合材料的界面面积、致密度及其镁基体的位错密度来实现的.     

微米级SiC颗粒增强铝基复合材料的强化机制

为了研究微米级碳化硅颗粒(SiCp)尺寸和含量对中体积分数SiCp增强铝基复合材料强化机制的影响,用粉末冶金工艺制备SiCp体积分数为30%~40%,颗粒尺寸为3~40μm的SiCp/2024Al复合材料,利用TEM,万能材料试验机等对材料微观结构和拉伸性能进行了研究。结果表明,复合材料的抗拉强度和硬度均随着SiC颗粒尺寸的增大而减小,随体积分数的增加而增大。复合材料的强化是由多种强化机制协同作用的结果,SiC颗粒尺寸主要通过位错强化和细晶强化显著影响对复合材料的强化效果。     

体育器材用SiCp/Al复合材料的制备和性能研究

研究了SiC颗粒尺寸和体积分数对SiCp/Al复合材料性能的影响。结果表明,在相同体积分数下,SiC颗粒粒径越小,对复合材料性能的改善效果越明显,5μm时效果最好。采用5μm的SiC颗粒,复合材料的抗拉强度、比强度随体积分数增大而先增后降,15%时达到最大,硬度随体积分数的增大而增大。综合来看,SiC颗粒粒径为5μm,体积分数为15%时,制备的材料性能最好。     

SiCp／Mg（AZ81）镁基复合材料制备工艺的优化

研究了不同铸造工艺条件下镁基复合材料的组织结构,并对其气孔率进行了测定。结果表明,随着搅拌温度的提高,复合材料的气孔率上升。当颗粒尺寸一定时,复合材料的气孔率随颗粒体积分数的增加而增加;当颗粒体积分数一定时,复合材料的气孔率随颗粒尺寸的增大而减少。搅熔铸造法制备的复合材料在颗粒分布及气孔含量方面均优于半固态搅拌铸造法和全液态搅拌铸造法。     

SiC对SiC/6066铝基复合材料挤压过程力学行为的影响

利用有限元方法分析了SiC颗粒在不同形状、体积分数时对Al基复合材料挤压过程力学行为的影响,并对试样进行了拉伸试验。结果表明,随着SiC颗粒角度减小,颗粒的应力很快增大,基体的应变呈增大趋势;随SiC颗粒体积分数的增大,颗粒的应力、基体的应变以及该复合材料的弹性模量及屈服强度呈增大的趋势。     

几何特征对SiC颗粒增强Al基复合材料力学行为的影响

利用有限元方法建立三维模型分析SiC颗粒在不同形状、不同体积分数和不同尺寸时对Al基复合材料力学行为的影响,并进行拉伸试验研究.结果表明,颗粒形状比颗粒尺寸和颗粒体积分数对材料的应力、应变分布及材料韧性的影响大.颗粒尖角附近有严重的应力集中现象,在外力方向上颗粒端部附近的基体上的应变也有集中现象.随颗粒角度的减小,颗粒的应力很快增大而韧性减小,材料的弹性模量有增大的趋势.随颗粒体积分数的增大,颗粒的应力有减小趋势,材料的弹性模量呈增大趋势.颗粒尺寸较小时(平均尺寸为5 μm),颗粒尺寸对材料的应力及应变的影响小.     

TiC增强高锰钢基复合材料的组织与磨料磨损性能

采用凝固析出方法制备了不同体积分数TiC增强的高锰钢基复合材料,系统研究了复合材料的显微组织和磨料磨损性能。热处理后,复合材料由奥氏体和TiC两相组成,TiC颗粒均匀分布在高锰钢基体中,颗粒与基体界面清洁。磨料磨损实验表明,TiC颗粒的引入提高了复合材料耐磨性能。然而,复合材料的耐磨损性能随着TiC体积分数的增加而降低。研究结果表明,随着TiC体积分数的提高,陶瓷颗粒尺寸增大且部分形成团簇,陶瓷颗粒在磨损过程中发生破碎从而提高磨损率。     

SiCp尺寸对铝基复合材料拉伸性能和断裂机制的影响

对粉末冶金法制备的不同尺寸SiCp增强铝基复合材料的拉伸性能进行了研究.结果表明,小尺寸SiCp（<7μm）复合材料断裂以界面处基体撕裂为主,强度较高.大尺寸 SiCp增强复合材料断裂以 SiCp解理为主,强度较低,但塑性比小尺寸颗粒增强复合材料要高.体积分数为17％,尺寸为7μm颗粒复合材料拉伸性能最好.     

铸造WC/Ni基合金复合材料二体磨料磨损性能的研究

用真空热压液相烧结技术制备铸造WC／Ni基合金复合材料。研究了铸造WC的颗粒尺寸及体积分数对复合材料的二体磨料磨损性能的影响，并将它与高铬铸铁(Cr28)相比较。结果表明：随着铸造碳化钨颗粒尺寸和体积分数的增大，复合材料的耐磨性提高，且远高于高铬铸铁。     

有限元模拟SiC增强Al基复合材料的力学行为

采用有限元方法和轴对称单胞模型模拟了增强体(SiC)形状、体积分数以及不同基体类型对铝基复合材料力学行为的影响。模拟结果表明:增强体的加入会阻碍基体的塑性流变,使基体内发生非均匀变形,在增强体尖角处出现应力集中;椭圆柱形增强体对基体塑性变形的阻力最大,传递载荷的能力最强,因此强化效果最好。在一定范围内,随着增强体体积分数的增加,基体与增强体之间的比表面积增大,有利于载荷的传递;增强体体积分数的增加导致颗粒间距减小,几何必须位错自由运动的路径减少,复合材料的强度也随之增加。此外,不同类型基体自身的塑性流变能力不同,Al-Zn-Mg基体强度最高,在拉伸变形过程中,受到增强体的阻碍作用最大,会有更多的载荷从基体传递到增强体,以Al-Zn-Mg为基体的复合材料的强度最高。     

Correlation between tensile and indentation behavior of particle-reinforced metal matrix composites: an experimental and numerical study

The correlation between tensile and indentation behavior in particle-reinforced metal matrix composites (MMCs) was examined. The model composite system consists of a Al–Cu–Mg alloy matrix reinforced with SiC particles. The effects of particle size, particle volume fraction, and matrix aging characteristics on the interrelationship between tensile strength and macro-hardness were investigated. Experimental data indicated that, contrary to what has been documented for a variety of monolithic metals and alloys, a simple relationship between hardness and tensile strength does not exist for MMCs. While processing-induced particle fracture greatly reduces the tensile strength, it does not significantly affect the deformation under indentation loading. Even in composites where processing-induced fracture was nonexistent (due to relatively small particle size), no unique correspondence between tensile strength and hardness was observed. At very low matrix strengths, the composites exhibited similar tensile strengths but the hardness increased with increasing particle concentration. Fractographic analyses showed that particle fracture caused by tensile testing is independent of matrix strength. The lack of unique strength–hardness correlation is not due to the particle fracture-induced weakening during the tensile test. It is proposed that, under indentation loading, enhanced matrix flow that contributes to a localized increase in particle concentration directly below the indenter results in a significant overestimation of the overall composite strength by the hardness test. Micromechanical modeling using the finite element method was used to illustrate the proposed mechanisms under indentation loading and to justify the experimental findings.     

Fatigue crack growth resistance of SiC<Subscript>p</Subscript> reinforced Al alloys: Effects of particle size,particle volume fraction,and matrix strength

The main aim of this work was to study the effects of particle size, particle volume fraction, and matrix strength on the long fatigue crack growth resistance of two different grades of Al alloys (Al2124-T1 and Al6061-T1) reinforced with SiC particles. Basically, it was found that an increase in particle volume fraction and particle size increases the fatigue crack growth resistance at near threshold and Paris regimen, with matrix strength having a smaller effect. Near final failure, the stronger and more brittle composites are affected more by static modes of failure as the applied maximum stress intensity factor (K _max) approaches mode I plane strain fracture toughness (K _IC).     

Microstructure-based modeling of the influence of particle spatial distribution and fracture on crack growth in particle-reinforced composites

The crack growth behavior of particle-reinforced composites is determined by several factors, such as volume fraction, particle size, particle morphology, spatial distribution and particle strength. Thus, an accurate and robust numerical model must incorporate the true microstructure of the particles. It will be shown that the strength of the reinforcement particles is also an important factor. Hence, the model must be able to simulate particle fracture. In this paper, the crack growth behavior of SiC particle-reinforced Al matrix composites was modeled using actual microstructures. Linear elastic fracture mechanics principles were used to propagate the crack and obtain the local stress intensity values. The effect of particle fracture on crack growth was studied. It will be shown that spatial distribution and shape of the particles, as well as particle fracture ahead of the crack tip, significantly affect the crack trajectory and the stress distribution at the crack tip.     

原位TiB2颗粒增强铝基复合材料及其力学性能

对原位反应合成TiB2／A356铝基复合材料微观组织和力学拉伸性能进行了研究。结果表明，原位反应生成的颗粒增强相在复合材料基体中分布均匀，基体与颗粒间的界面洁净。复合材料强度随着颗粒含量的增加显著提高，与基体合金相比，TiB2质量分数为8％的TiB2／A356复合材料强度和弹性模量的提高幅度约为28％，TiB2质量分数为16％的TiB2／A356复合材料强度和弹性模量的提高幅度约为35％。复合材料的断裂主要是由于基体与颗粒界面脱粘，在拉伸应力作用下由此萌生微裂纹并扩展，导致界面处的基体撕裂，从而降低复合材料塑性。     

不同磨料粒度下WC体积分数对铁基表面复合材料磨损性能的影响

用负压铸渗工艺制备了WC/HT300基表面复合材料,研究了WC体积分数和冲蚀磨损浆料中的颗粒粒度对复合材料的抗冲蚀磨损性能的影响。对于同一种WC颗粒体积分数的复合材料,当浆料中的石英砂粒度大时,复合材料的体积磨损率较大,抗冲蚀磨损性能降低。WC体积分数为27%和36%的表面复合材料具有比其他WC体积分数复合材料优越的耐磨损性能;在磨料粒度为40~70目的工况下,WC体积分数为36%的复合材料,具有比体积分数为27%的复合材料优越的耐磨性能;但在磨料粒度增大到20~40目时,WC体积分数为27%的复合材料,具有比WC体积分数为36%的复合材料优越的耐磨损性能。     

SiC颗粒增强铝基复合材料的热循环行为研究

基于材料微观组织建立了视场胞元模型,并采用商用有限元软件ABAQUS对胞元模型进行温度循环的数值模拟,着重分析热循环中基体和增强颗粒的等效应力分布规律,及主应力σ_(11)和σ_(22)的分布规律.结果表明:在热循环的升温阶段,基体的主热应力整体表现为压应力,增强颗粒表现为拉应力;在降温阶段,基体表现为拉应力,增强颗粒表现为压应力;在模拟中,对3次循环中的主热应力σ_(22)做了统计,发现不论是基体还是增强颗粒,从第2次循环开始,热应力就开始趋于稳定.通过改变单元胞中颗粒的体积分数进一步分析体积分数变化对颗粒增强金属基复合材料热循环的影响,结果发现体积分数减小之后,基体和增强颗粒应力分布变得均匀,并且各次循环中的热应力相差不大,比较稳定.最后对热循环中的应变滞后回线进行了分析,表明高体积分数下的复合材料具有高的热稳定性.     

SiCp增强镁基复合材料微区应力场的仿真模拟

采用有限元方法仿真模拟了SiC颗粒(SiCp)增强镁基复合材料中实际形状的增强体周围的微区应力场。结果表明，不同形状的增强体颗粒附近的微区应力场差异很大，个别颗粒会在低应力下失效．当增强体的体积分数较少时，每个增强体的微区应力场受其它增强体影响不大，近似给出单个增强体的形状就可以仿真模拟增强体附近的微区应力场．利用粉末冶金法制备了颗粒增强镁基复合材料，观察其拉伸断口，并利用有限元方法进行仿真模拟，据此进行了增强体颗粒的失效分析。     

Co-electrodeposition and characterization of Cu-Si3N4 composite coatings

Smooth copper coatings containing well-distributed silicon nitride particles were obtained by co-electrodeposition in acidic sulfate bath. The cathodic current density did not show significant influence on incorporated particle volume fraction, whereas the increase of particle concentration in the bath led to its decrease. The increase of stirring rate increased the amount of embedded particles. The microhardness of the composite layers was higher than that of pure copper deposits obtained under the same conditions due to dispersion-strengthening and copper matrix grain refinement and increased with the increase of incorporated particle volume fraction. The microhardness of composites also increased with the increase of current density due to copper matrix grain refining. The composite coatings presented higher strength but lower ductility than pure copper layers. Pure copper and composite coatings showed the same corrosion resistance in 0.5 wt.% H₂SO₄ solution at room temperature.