Fracture Behavior of Particle Reinforced Metal Matrix Composites

The contributions of the reinforcement volume fraction and annealing temperatures to crack opening force and propagation energy are systematically studied by three point bending tests and by SEM investigations. The bending test data show that for the same reinforcement volume fraction, 2618 and 7075 Al composites require much higher force to open the cracks than 6061 matrix. This relates to the much higher levels of solute elements which causes matrix hardening. Studies reveal that the energy absorption level of the materials during crack propagation depends on both matrix strength and ductility which relates to the reinforcement volume fraction, composition and heat treatment conditions. Large deformation zones are found in front of the crack tip before crack propagation which indicate a ductile failure mode for the composites. Studies also reveal that cracks initiate generally at the particle/matrix interfaces for the low volume fraction reinforced composites. However, for the high volume fraction reinforced composites, crack initiation has been found from both reinforcement/matrix interfaces and broken particles. This indicates that increasing reinforcement volume fraction and matrix strengthening tend to change the fracture mode from interface debonding to particle cleavage cracking.     

颗粒强化金属基复合材料的原位合成工艺

介绍了颗粒强化金属基复合材料(MMCs)的原位合成工艺,工艺主要可分为:固-液、固-固、液-液、气-液和气-反应5类,并分别对各类合成工艺的合成方法、优缺点、研究进展进行了详细的阐述.最后对目前原位合成颗粒增强MMCs存在的问题作了归纳总结.     

颗粒增强金属基复合材料微屈服行为的细观力学计算

本文采用细观力学模型 ,计算了颗粒增强金属基复合材料的微屈服行为规律。计算模型是以有限元法、应力二阶矩的割线模量法、Eshelby等有效夹杂方法和双夹杂模型等为基础。计算结果表明在基体材料的微屈服规律符合Brown Lukens线性规律的情况下 ,颗粒增强金属基复合材料的σ 〈εp〉1 2 关系也近似呈线性符合Brown Lukens规律。同时计算了增强体颗粒的含量、热残余应力和位错密度等多方面因素对复合材料微屈服规律的影响。     

颗粒增强铝基复合材料的疲劳研究进展

对近年来颗粒增强铝基复合材料疲劳性能研究进展进行了总结,介绍了颗粒增强铝基复合材料的强化机制,概括了影响材料疲劳性能的几个重要的因素,从裂纹萌生以及裂纹扩展方面阐述了其疲劳行为及微观失效机制,并提出了未来颗粒增强铝基复合材料的研究趋势。     

有界面脱粘时颗粒增强金属基复合材料的弹塑性性能分析

基于Mori-Tanaka理论和Eshelby等效夹杂理论,假定基体和增强相界面结合完好,推导出在力的边界条件下两相复合材料各组成相的应力、应变以及复合材料的体平均应变和应力,并考虑了基体和增强颗粒热膨胀系数引起的热应变以及各相塑性应变的影响.在此基础上,假定基体和复合材料均为各向同性材料,颗粒仅产生弹性变形,基体产生弹塑性变形且满足Mises屈服准则和等向强化准则,由颗粒所受的拉应力控制界面的脱粘,脱粘概率由Weibull分布函数来描述,脱粘后的颗粒等效为孔洞,采用割线模量法讨论了球形颗粒增强金属基复合材料有界面脱粘时的弹塑性性能,理论预测与实验结果吻合较好.     

Friction Stir Welding of Ceramic Particle Reinforced Aluminium Based Metal Matrix Composites

The mechanical and microstructural properties of 6061+20% Al₂O_3p and 7005+10% Al₂O_3p aluminium based metal matrix composites joined by friction stir welding were analyzed in the present study. The two materials were welded into the form of sheets of 7 mm thickness after T6 treatment and were tested in tension at room temperature. The microstructure of the joints was observed by optical microscopy and the fracture surfaces were analyzed by employing a scanning electron microscope equipped with field emission gun in order to study the micromechanisms involved during the deformation.     

Friction Stir Welding of Ceramic Particle Reinforced Aluminium Based Metal Matrix Composites

The mechanical and microstructural properties of 6061+20% Al₂O_3p and 7005+10% Al₂O_3p aluminium based metal matrix composites joined by friction stir welding were analyzed in the present study. The two materials were welded into the form of sheets of 7 mm thickness after T6 treatment and were tested in tension at room temperature. The microstructure of the joints was observed by optical microscopy and the fracture surfaces were analyzed by employing a scanning electron microscope equipped with field emission gun in order to study the micromechanisms involved during the deformation.     

颗粒增强金属基复合材料强化理论模型研究与发展

简要介绍了等效夹杂、平均应力场以及应变梯度塑性理论等几种常用颗粒增强金属基复合材料强化理论模型的发展情况,总结了国内外学者对各强化理论模型的修正情况,讨论了各强化理论模型的优缺点以及适用性,提出了颗粒增强金属基复合材料强化理论模型的发展方向。     

短纤维增强金属基复合材料微屈服行为的计算机模拟

本文采用细观力学模型 ,根据Eshelby等效夹杂原理和双夹杂模型等 ,用计算机模拟的方法定量计算了短纤维增强金属基复合材料微屈服行为规律。计算结果表明在基体材料的微屈服规律符合Brown Lukens线性规律的情况下 ,金属基复合材料的σ - <εp>1 2 也近似符合Brown Lukens规律。同时计算了增强体短纤维的含量、形状、热残余应力和位错密度等多方面因素对复合材料微屈服规律的影响     

颗粒增强金属基复合材料的结构建模与力学模拟研究进展

颗粒增强金属基复合材料具有高模量、高强度及高耐磨等优异性能,其材料体系庞杂、复合结构繁复,力学性能指标众多。通过结构建模与力学模拟的系统研究,能够有效揭示复合材料的构效关系与组织演变规律,进而指导其设计、制备、加工与应用全流程研究。开展多尺度建模计算,并与宏、微观实验相融合,以及利用以数据库技术、高通量计算与大数据挖掘为主要特征的材料信息学研究,可实现金属基复合材料的“组分-工艺-结构-性能”内禀关系的科学内涵描述。首先回顾了颗粒增强金属基复合材料建模计算的主要研究方法,然后对其结构建模研究现状进行了介绍,进而围绕界面特性与力学模拟进行了综合述评,最后对建模拟实结合材料基因工程技术的未来发展进行了展望。     

选区激光熔化制备颗粒增强金属基复合材料的研究进展

选区激光熔化是一种使用聚焦高能激光束熔化粉末,逐层叠加成形零件的增材制造方法.选区激光熔化可以直接制备复杂结构零件和实现近净成形,能够方便地通过粉末预混添加或原位反应实现颗粒增强金属基复合材料的控形控性,具有独特的技术优势,受到广泛关注.本文综述了选区激光熔化制备颗粒增强金属基复合材料的研究进展,总结了主要研究结果及存在的共性问题,并展望了选区激光熔化制备颗粒增强金属基复合材料的研究方向和发展趋势.通过总结分析,指出选区激光熔化制备颗粒增强金属基复合材料时,聚焦激光作用下形成的高温微小熔池凝固时间短,远远偏离平衡状态,凝固过程复杂,增强颗粒与基体间冶金反应剧烈,容易熔化、分解和溶解并对基体特性产生影响,进而影响成形后的复合材料的宏观形貌和组织、性能.除增强体成分、颗粒形貌与尺寸、体积分数外,复合材料的性能还受激光功率、扫描速度、扫描间距、粉层厚度、成形气氛等工艺参数的影响,粉末特性与工艺参数之间的交互作用复杂.因此,考察工艺参数与粉末特性之间的交互作用关系,系统研究增强体颗粒特性与成形工艺参数对复合材料宏观形貌、致密度、缺陷、组织和性能的影响规律,是实现复合材料组织结构设计和性能调控的基础.     

Processing and Characterization of Fiber Reinforced Intermetallic Matrix Composites

A series of intermetallic matrix composites reinforced with Al₂O₃ based fibers were fabricated by pressure casting. The Al₂O₃ based fibers used were DuPont's 20 μm diameter Fiber FP and PRD-166 fiber, Mitsui's 10 μm diameter Almax fiber, and Saphikon's 125 μm diameter single crystal Al₂O₃ fiber. The intermetallic matrices employed were alloys based on Ni₃Al, NiAl, Fe₃Al, Ti₃Al+TiAl, and Nb₂Al+NbAl₃. Optical, scanning and transmission electron microscopy were used to investigate the microstructure of the composites and the fibers. Tensile testing was conducted to determine the Weibull mean strength of the fibers in the as-received and heat treated conditions. The effect of fiber gage length on the Weibull mean strength of the PRD-166 and Fiber FP was evaluated. Indentation tests were performed to determine the effect of alloying additions on the fiber/matrix bond strength in shear in Saphikon fiber reinforced Ni₃Al composites.     

连续纤维增强陶瓷基复合材料概述

八十年代以来 ,连续纤维增强陶瓷基复合材料以其优异的性能特别是高韧性 ,得到世界各国的极大关注和高度重视 ,并取得令人瞩目的发展。纤维增强陶瓷基复合材料已开始在航空、航天、国防等领域得到应用。本文从复合材料的增韧机制、制备方法、界面特性和界面改性以及应用等方面综述了国内外有关连续纤维增强陶瓷基复合材料的研究现状     

电镀镍碳纤维增强铝基复合材料

提出一种碳纤维表面电镀镍的方法,通过正交实验优化了电镀镍配方及工艺条件,并研究了镀层的显微组织及镀液的成分、电流密度、电镀时间等工艺条件对沉镍速率和镀层质量的影响,并探讨了沉镍机理.用镀镍碳纤维制备铝基复合材料,观测碳纤维与铝的复合效果.     

颗粒增强铝基复合材料阳极氧化与耐蚀性的研究

基体中加入与铝合金基体电位不同、高体积分数的碳化硅和石墨颗粒增强材料,可能导致材料的耐蚀性降低.采用盐雾腐蚀和硬质阳极氧化方法对4种喷射沉积制备的颗粒增强铝基复合材料和一种喷射沉积锭坯颗粒增强铝基复合材料的腐蚀行为及阳极氧化工艺进行了研究.结果表明,颗粒增强铝基复合材料具有较高的腐蚀率,腐蚀形态均为明显的点蚀;在适当阳极氧化工艺条件下,颗粒增强铝基复合材料表面可以制得优良耐蚀性的硬质阳极氧化膜.     

A Novel Processing Technique for Tow Fiber Reinforced Metal Matrix Composites with Tailored Interfaces

A novel metal matrix composite processing technique based upon plasma-assisted physical vapor deposition (PVD) of metais/alloys has been developed wherein, starting with lower cost tow fibers, the tows are spread to separate the individual filaments and then each filament coated uniformly with the matrix by plasma sputtering inside a hollow cathode magnetron. The coated fibers are then densified into a composite. This technique allows the synthesis of metal matrix composites with high fiber volume fractions. The resulting composite exhibits a uniform microstructure with complete infiltration of the matrix. Further, the plasma-assisted deposition process spares the tow filaments from severe strength degradation normally associated with melt-infiltration processing. Also, for chemically or thermo-mechanically incompatible fiber-matrix systems, the technique allows the incorporation of an interfacial layer (engineered for greater chemical inertness or lower residual stresses) prior to the deposition of the matrix. This technique has been applied here to synthesize composites based on Nextel 610 tows and Superalloy matrices (Thermo-span, Haynes 214 or Inconel 718) with a Mo chemical barrier layer.     

颗粒增强金属基表面复合材料的研制

为了提高金属材料的表面综合性能,作者研究了用快干涂料铸渗法来制造颗粒增强金属基表面复合材料的工艺,通过大量试验,开发出了一种新型的铸渗用快干涂料;分析了复合层的显微组织和主要质量影响因素,研究表明,直接用铸造的方法可在铸件表面形成同时具备外硬内韧、耐磨,耐热,耐蚀等优良综合性能的颗粒增强金属基表面复合材料,结果表明,浇注温度影响复合质量的最主要因素,在1450－1550℃范围内均能获得优良的表面复合层;表面复合材料的硬度在60HRC以上,是普通耐磨铸铁硬度的1．4－1．6倍,这是一种工艺简单,成本低且有广阔前途的新工艺。     

碳纤维增强铜基复合材料摩擦与磨损行为的研究

研究了用热压法制造的碳纤维增强铜—5％锡基复合材料的摩擦磨损行为。对碳纤维的体积分数改变时,复合材料的摩擦系数,磨损速率的变化规律作了分析,进行了磨屑成分分析及磨面的形貌观察,初步提出了这种复合材料的磨损机制。实验结果表明:随着碳纤维含量的增加,复合材料的摩擦系数下降、磨损率减小,认为在给定的实验条件下,“碳纤维/铜—5％锡”复合材料的磨损是粘着和氧化共同作用的结果,在高温下或纤维体积含量较高时,氧化磨损是主要磨损形式。     

碳纤维增强铜基复合材料研究进展

本文综述了碳纤维在铜基复合材料中的作用及其表面处理技术的发展现状。总结了近年来碳纤维表面改性方法以及存在的主要问题,分析了碳纤维对铜基复合材料组织的形成及其性能的影响。最后展望了碳纤维的发展前景。