金属基复合材料制备技术的应用及其发展

金属基复合材料(Metal Matrix Composite)是采用特殊的工艺手段,将不同种类、不同形态的陶瓷,非金属增强相均匀分布在连续的金属基体中而获得的一类新型材料。它的性能兼备了金属基体与增强相     

0Cr18Ni9/ZL107网络互穿复合材料加工表面缺陷研究

对0Cr18Ni9/ZL107网络互穿复合材料进行了车削试验研究。研究结果表明,网络互穿复合材料两相材料界面处的车削加工缺陷主要表现为增强相与基体相之间的裂纹以及增强相与基体相的分离翘曲,复合材料表面的加工缺陷主要表现为增强相凹凸、基体撕裂以及基体表面微裂纹。试验证明,减小进给量和切削深度,增大切削速度能够有效控制车削加工表面缺陷。     

三维网络结构SiC-Fe复合材料制备及腐蚀性能研究*

传统钢铁材料难以满足深井开采严苛的腐蚀环境,亟需开发具有良好耐蚀性的新材料。SiC陶瓷具有优异的耐蚀性,因此探讨了以SiC为原材料的复合材料的制备及耐蚀性。以SiC、Al2O3、SiO2为原材料采用有机泡沫浸渍法制备出三维网络结构SiC陶瓷,并采用浇铸工艺制备三维网络结构SiC-Fe复合材料,采用扫描电子显微镜、X射线衍射仪等对SiC-Fe复合材料组织结构及物相进行分析,通过电化学试验、浸泡试验对SiC-Fe复合材料的耐蚀性进行表征,并分析其耐腐蚀机制。结果表明：SiC-Fe复合材料中SiC陶瓷增强体与高铬铸铁基体之间未发生元素扩散,界面结合方式为机械结合,基体中主要物相有奥氏体和碳化物,陶瓷增强体中主要为六方结构SiC和Al2O3;SiC陶瓷增强体的加入使高铬铸铁的腐蚀电流由4.189×10-3 A/cm2降至3.353×10-3 A/cm2,电荷转移电阻从7.309 Ω·cm2增大至11 881 Ω·cm2,电容值从1.994×10-4 F/cm2降至1.974×10-5 F/cm2,使整体的耐蚀性得到了提高。浸泡试验表明,SiC-Fe复合材料的腐蚀主要发生在高铬铸铁基体部分,界面及SiC陶瓷增强体处不易发生腐蚀;与纯高铬铸铁材料相比,SiC-Fe复合材料点蚀产生的时间较晚且腐蚀程度相对较轻。研究成果为复合材料在煤矿深井开采装备的应用提供重要理论依据。     

晶须与颗粒混合增强陶瓷基复合材料的相平均应力及微区应力分布特征分析

采用三维有限元法在MSC-MARC软件中模拟不同性质的晶须和颗粒混合增强陶瓷基复合材料时微区应力分布特征,并计算增强相及基体平均应力。结合Eshelby夹杂理论和Mori-Tanaka方法推导增强相及基体的平均应力的理论公式,将两种方法所得的结果进行比较。结果表明,理论模型与有限元法得到的各相平均应力非常吻合,不同形状的增强相分担的应力差异很大,晶须增强相能够分担大部分的平均应力,对降低基体应力、提高多相混合增强陶瓷基复合材料的强度起主要作用。数值模拟结果同时给出微区应力场分布特征,显示晶须位置变化和晶须弹性模量变化对微区应力分布均有一定影响,有利于对多相增强复合材料进行失效分析。颗粒增强相具有调节晶须分布位置,有效改善微区应力分布特征的作用。     

颗粒增强脆性基体复合材料的细观强度模型

用细观力学的方法研究颗粒增强脆性基体复合材料的强度和损伤失效,认为复合材料由随机二相胞元和基体构成,分析基体、颗粒中的局部应力场,根据损伤理论分别得到基体和颗粒的损伤等效应力.在界面脱开成为裂纹源并向基体内扩展的情况下,计算出弧形界面裂纹的能量释放率.最后分别提出基体、颗粒和界面的失效强度准则.结果表明, 复合材料的强度与二相胞元的方位角、颗粒体积含量、界面脱粘角、颗粒直径有关.     

不同铝基体SiC_p/Al复合材料切削力与刀具的磨损研究

对不同增强相体分比、颗粒尺寸和基体材料的Si CP/Al复合材料进行切削试验,分析了铝基体材料和颗粒尺寸对高、低增强相体分比Si C_p/Al复合材料切削力的影响。针对Si C_p/Al复合材料切削力的复杂性,提出用分形维数的方法定量描述切削力波动的复杂程度。对不同铝基体Si C_p/Al复合材料进行刀具磨损试验,研究铝基体对刀具磨损的影响。结果表明:随着增强相体分比和颗粒尺寸的增加,铝基体对切削力的影响减弱;随着增强相体分比增加,颗粒尺寸对于切削力影响有增大趋势;分形维数可以定量描述切削力波动性质,且Si C_p/6063Al切削力波动频率高于Si C_p/2024Al;相对于Si C_p/2024Al,切削Si C_p/6063Al时刀具前刀面粘结磨损加剧而颗粒磨损减少,刀具后刀面磨损程度相对较高。     

高熵合金增强铝基复合材料组织与显微硬度研究

以5083铝合金为基体,以FeCoNiCrMn高熵合金颗粒为增强相,通过搅拌摩擦加工技术制备了颗粒增强铝基复合材料,研究了加工道次对复合材料微观组织和显微硬度的影响。研究结果表明:增加加工道次可以使得FeCoNiCrMn高熵合金颗粒在基体中分散更加均匀,显微硬度结果显示添加FeCoNiCrMn高熵合金颗粒后复合材料硬度得到大幅度提升,且5道次加工后的显微硬度最高。     

铸造烧结法制备表面铁基复合材料的致密化机理及耐磨性能

用SEM、XRD等分析了用铸造烧结法在HT200灰铸铁表面制备的复合材料的组织与物相组成,用EDS分析了该复合材料与基体结合界面的元素分布,分析了其致密化机理;测试了此复合材料的耐磨性能。结果表明:在铸造烧结过程中,压坯中的σ-(FeV)相迅速分解出α-Fe和钒,V_8C_7相的强放热反应及铁液传递给压坯的热流密度保证了压坯迅速完成烧结致密化,得到由微米V_8C_7颗粒和α-Fe相组成的复合材料,增强相颗粒与基体相结合良好;复合材料与灰铸铁形成了冶金结合;在重载、干滑动摩擦条件下,此复合材料的耐磨性比淬火45钢提高了44.5倍。     

直接金属氧化法制备SiCp/Al2O3-Al复合材料

利用直接金属氧化法制备了SiC颗粒增强Al2O3-Al基复合材料，借助于XRD和光学显微镜对该复合材料的组成及微观结构进行了观察，分析了SiO2层、合金成分和制备温度对复合材料性能的影响。结果表明：该复合材料结构致密且渗透完全，微观结构由三种相互穿插相组成：SiC预制体、连续的Al2O3基体及呈网状结构分布的未被氧化的残余铝合金。     

第一切削变形区中SiC增强相的重定向研究

介绍了切削SiC非连续增强铝基复合材料时第一切削变形区的材料变形情况,推导了SiC增强相的转角公式,并用试验结果验证了SiC增强相的重定向现象。结果表明,第一切削变形区中的SiC增强相发生了重新定向运动,转向了铝基体的纤维化方向,转角大小会因SiC增强相在第一切削变形区中的具体位置和原位向的不同而存在差异。SiC增强相重定向后并不与剪切面重合,而是成一定角度。第一切削变形区的宽度与切削铝基体材料相比要大。     

The mechanical behaviour of interpenetrating phase composites – II: a case study of a three-dimensionally printed material

Interpenetrating phase composites (IPCs) – composites in which each phase forms a completely interconnected network – are becoming an important class of materials as the result of the development of a number of new techniques for producing composites with interpenetrating microstructures. In this paper, the mechanical properties of two-phase IPCs are modelled. Finite element analysis is used to investigate elastic, strength, and thermal expansion properties of IPCs. The numerical results are compared with the properties of composites with non-interpenetrating microstructures. For the specific microstructures investigated, it is found that a composite with an interpenetrating microstructure can possess enhanced thermo-mechanical properties. The enhanced properties may result more from the contiguity of the phase with more advantageous properties than from the interpenetrating microstructure.     

The mechanical behaviour of interpenetrating phase composites — III: resin-impregnated porous stainless steel

Powder metallurgy (P/M) derived porous metals that have been impregnated with a polymer resin to create fully dense composites are examples of interpenetrating phase composites (IPCs), in which each phase forms a completely interconnected network. In this paper, we describe an experimental and modelling investigation of the mechanical properties of resin-impregnated P/M derived porous 316L stainless steel composites of various volume fractions, with a view to gaining a better understanding of the mechanical properties of IPCs. In comparison with a similar investigation of 420 stainless/bronze IPCs, properties of the 316L stainless/resin IPCs are less well represented by non-linear finite element analysis based on a unit cell model with periodic boundary conditions. This is attributed to the more irregular microstructure of the 316L/resin IPCs, greater uncertainty in the properties of the constituent materials, and larger differences between constituent properties. Considering only mechanical properties, the 316L stainless/resin combination does not appear to take advantage of the interpenetrating phase morphology, since the resin does not possess a superior property to contribute to the composite as a whole.     

The potential of hydrogels as synthetic articular cartilage

The relatively poor mechanical properties of conventional synthetic hydrogels are illustrated and compared with those of articular cartilage. By using the composite structure of the natural material as a model a new family of hydrogels, based on interpenetrating polymer network (IPN) technology, has been developed. The underlying synthetic strategies are discussed and the properties of a novel representative network presented. IPN formation produces networks that are stiffer and stronger than the hydrogel copolymers of similar water content. In this behaviour these simple IPNs begin to mimic the properties of biological hydrogel composites. Thus, these materials have exciting potential for demanding in vivo applications.     

The scratch behaviour of aluminium composite coatings

Wear data obtained from single and multiple scratch passes, combined with the examination of the reinforcement-matrix interfacial structure by transmission electron microscopy (TEM) and toughness measurements made on the reinforcement phase, wereused to evaluate the wear behaviour of aluminium-based composite coatings. Reinforcement properties such as reinforcement volume fraction (V_f ), size, interfacial bonding and toughness appear to be important variables in deciding the abrasive wear resistanceof composite coatings. Scratch testing appears to be a valuable tool in providing information regarding the nature of the reinforcement-matrix interfacial structure, which is a deciding parameter in the abrasive wear resistance of metal matrix composite (MMC)coatings.     

Microstructural analysis of iron aluminide formed by self-propagating high-temperature synthesis mechanism in aluminium matrix composite

An aluminium matrix composite with iron aluminide formed in situ as a result of self‐propagated high‐temperature synthesis was examined. The structural characteristics of the reinforcement investigated by scanning electron microscopy and transmission electron microscopy methods are presented. Iron aluminide particles with a very fine grain size and of two shapes, cubic and needle‐like, were observed. No differences in their phase composition were found by the selective electron diffraction pattern method. The composite reinforcement formed in the early stage of self‐propagating high‐temperature synthesis consisted only of the Al₃Fe phase.     

The application of magnetic structural phase analysis for the diagnostics of the State of a 08X18H10T Steel-Ct3 Steel composite material and its components that were subjected to plastic deformation

The use of composite, in particular, multilayer materials, is one way to decrease the specific quantity of metal in an item and to increase its service characteristics. To develop methods for the diagnostic of the state of such composite materials and their components, the effect of cold rolling on the structure, magnetic, and mechanical properties of a two-ply composite material and its separate components was studied; the material was prepared by explosion welding of austenitic corrosion-resistant and low-carbon steels. It was shown that magnetic characteristics can be used for estimating the degree of deformation by rolling, phase composition, and mechanical properties of both two-ply 08X18H10T Steel-C^t3 Steel composite material as a whole and its separate components.     

Effect of the cutting condition and the reinforcement phase on the thermal load of the workpiece when dry turning aluminum metal matrix composites

Aluminum metal matrix composites (Al-MMCs) are two-phase high-performance materials. The reinforcement of aluminum alloys enhances the properties of the composite material but leads to poor machinability. The required mechanical work for machining is mostly dissipated into heat. Considerable generated quantities of heat are therefore expected when machining Al-MMCs due to the poor machinability of these composite materials. The machine tool, the tool, and the workpiece are thus subjected to a thermal load, which decreases the accuracy of machining. The thermal load increases moreover when dry turning due to the missing heat convection through the cutting fluid. It is therefore necessary to investigate the effect of the reinforcement phase and the cutting condition used on the thermal load of the workpiece in dry turning. Therefore, composites with different reinforcement phases and the non-reinforced aluminum matrix were used as the workpiece materials. The reinforcement differs regarding the volume percent and the average size of the silicon carbide particulate reinforcements. The results revealed that the thermal load and the thermal expansion of the workpiece are significantly affected by the cutting condition used and the reinforcement phase. High cutting speeds and feeds and moderate depths of cut need to be used in order to decrease the thermal load of the workpiece. The Al-MMC workpieces are subjected to greater thermal loads than the workpieces of the non-reinforced alloy. However, better machining accuracies were achieved in dry turning the Al-MMCs.     

Effects of Morphological Characteristics of Alumina Particles and Interfacial Bonding Strength on Wear Behavior of Nano/Micro-alumina Particulates Reinforced Al/A206 Matrix Composites

Matrix/reinforcement interface has a critical role in determining the properties of metal matrix composites (MMCs). Properties of matrix/reinforcement interface depend on the fabrication method. The main problem in the fabrication of MMCs is wettability between reinforcing particles and molten alloy. Al206/5 vol% alumina_p cast composites were fabricated by the addition of reinforcing particles into molten Al alloy, semi-solid and liquid states, in two different forms: (1) as-received alumina (nano/micro) particles and (2) pre-synthesized composite reinforcement prepared via ball milling of alumina (nano/micro) with Al and Mg powders (master metal matrix composite). The effects of powder addition techniques, alumina/matrix interfacial bonding strength, and morphological characteristics of alumina particles on wear behavior were investigated. A new combination parameter, called alumina particle appearance (APA) index, was introduced. APA index approximates the collective effects of morphological characteristics of alumina particles on wear behavior. It is suggested that samples with lower APA index have superior wear properties. Microscopic examinations of the composite and matrix alloy and alumina/matrix interface were studied by scanning electron microscopy and transmission electron microscopy. It was found that wear resistance was increased in the composites fabricated by the addition of pre-synthesized reinforcing particles into molten alloy in the semi-solid state. Improvement in wear resistance is attributed to higher bonding strength of matrix/reinforcement as well lower APA index compared to those prepared via as-received alumina particles.     

Microstructure and Wear Properties of In Situ Synthesized VC Carbide Reinforced Fe-based Surface Composite Coating Produced by Laser Cladding

In situ synthesized VC carbide particles reinforced Fe-based composite coating was fabricated by laser cladding on steel substrate using ferrovanadium (Fe–V) alloy and graphite as the precursor powders. The phase structure and microstructure of the clad layer were investigated by means of X-ray diffraction analysis, scanning electron microscopy, and electron probe microanalysis. Results showed that uniformly distributed VC particles with the radial dendrites shape could be synthesized by the in situ reaction. The hardness and wear properties of the clad coatings were greatly improved due to the presence of VC particles in comparison with the substrate.     

Revealing the 3D internal structure of natural polymer microcomposites using X-ray ultra microtomography

Properties of composite materials are directly affected by the spatial arrangement of reinforcement and matrix. In this research, partially hydrolysed cellulose microcrystals were used to fabricate polycaprolactone microcomposites. The spatial distribution of cellulose microcrystals was characterized by a newly developed technique of X-ray ultra microscopy and microtomography. The phase and absorption contrast imaging of X-ray ultra microscopy revealed two-dimensional and three-dimensional information on CMC distribution in polymer matrices. The highest contrast and flux (signal-to-noise ratio) were obtained using vanadium foil targets with the accelerating voltage of 30 keV and beam current of >200 nA. The spatial distribution of cellulose microcrystals was correlated to the mechanical properties of the microcomposites. It was observed that heterogeneous distribution and clustering of cellulose microcrystals resulted in degradation of tensile strength and elastic modulus of composites. The utilization of X-ray ultra microscopy can open up new opportunities for composite researchers to explore the internal structure of microcomposites. X-ray ultra microscopy sample preparation is relatively simple in comparison to transmission electron microscopy and the spatial information is gathered at much larger scale.