Effect of Centrifugal Speed in Abrasive Wear Behavior of Al-Si5Cu3/SiC Functionally Graded Composite Fabricated by Centrifugal Casting

Centrifugal casting was adopted for fabricating AlSi5Cu3/10 wt% SiC functionally graded metal matrix composite under three different centrifugal speeds of 800, 1000 and 1200 rpm, and hollow cylindrical components (φ_out 150 × φ_in 132 × 150 mm) were obtained. Microstructures of outer and inner periphery of all composites were observed through optical microscope and micro hardness of outer, intermediate and inner region of composite was tested using Vicker’s hardness tester. Results revealed that outer region of the composites centrifuged at all speeds have particle rich region with higher hardness. Abrasive wear experiments were conducted only on surface of particle rich region based on Taguchi’s technique by varying parameters such as centrifugal speed of casting process, rotating speed and applied load of abrasive wear tester. Analysis of variance results revealed that, centrifugal speed had highest significance on wear rate. Abraded surfaces were examined using scanning electron microscope and the maximum wear resistance was observed on particle rich zone of composite centrifuged at 1200 rpm.     

Experimental Analysis on Three Body Abrasive Wear Behaviour of Stir Cast Al LM 25/TiC Metal Matrix Composite

In this paper, the abrasive wear behavior of Al LM 25/10 wt% TiC metal matrix composite has been studied experimentally. The composite specimens were fabricated using stir casting technique. Microstructural evaluation revealed uniform distribution of reinforcement particles throughout the matrix. Abrasive wear experiments were designed for different values of load, speed and time through response surface methodology and were performed using three body abrasion tester. Surface plots for wear rate against all combinations of parameters revealed that wear rate increased with increasing load and time, but decreased with increasing speed. The generated regression equation established proper relation between parameters and wear rate, confirming the accuracy of the developed model. The results of optimization of process parameters revealed that a minimum wear rate of 0.00104 mm³/Nm was obtained at 27 N, 139 rpm and 3 min. Scanning electron microscope analysis results substantiated that wear rate was comparatively more at higher loads.     

Investigation of Production and Abrasive Wear Behavior of Functionally Graded TiB 2 /Al and TiB 2 /Al–4Cu Composites

In this study, it is aimed to investigate the production and abrasive wear properties of functionally graded TiB2/Al and TiB2/Al–4Cu composites. Using in situ technique, titanium di-boride (TiB2) particles are being spontaneously formed in liquid matrix, resulting in a “Al(l) + TiB2(S)” semisolid at 900 °C. The semisolid solidifies under a centrifugal force at 1500 rpm rotation speed in a steel mold to produce functionally graded composites. The properties of composites such as density, abrasive wear, hardness and microstructure were examined by dividing into four zones from the outside to the inside of the composite. Volume loss of composites were examined by using L16(4124) orthogonal design, considering some factors such as matrix type of composites, region of composites, abrasive particle size, sliding speed and sliding load according to Taguchi method. The results showed that both TiB2/Al and TiB2/Al–Cu composites had two regions: the TiB2-reinforced and non-reinforced regions. It was determined that the volume loss increased with increasing load, speed and abrasive particle size and decreased with increasing TiB2 particles reinforcement ratio.     

Mechanical Properties and Friction／Wear Behavior of Copper Alloyed Powder Composites

Copper alloyed powder composites containing nanoparticles were developed by hot pressing. Effects of nanoscale activated sintering aid and fine ceramic particles Al2O3 on hardness, working quality, and behaviors of friction and wear of the composites have been studied, compared with the composites including mieroscale activated sintering aid and microscale ceramic particles. The microstructures of the samples were analyzed by SEM. The resuits show that the materials with nanoscale sintering aid and fine ceramic particles have better mechanical properties and abrasive resistance than the materials with microscale activated sintering aid and microceramic particles. Moreover, element mutual transfer occurs between samples (strip) and abrasive wheel (ring).     

聚变堆面向等离子体SiC/Cu梯度材料的制备与评价

用超高压梯度烧结法制备出了成分分布从0~100%的接近理论密度的SiC/Cu聚变堆面向等离子体功能梯度材料.化学溅射实验表明其CD₄产额与二次纯化石墨相比降低了80%;热解吸放气率约为石墨的10%;在398MW/m²的激光热冲击下,材料表面出现疲劳裂纹和化学分解现象;原位等离子体辐照结果显示陶瓷材料表面出现一定程度的溅射损伤.     

Micromechanical Investigation of the Fatigue Crack Propagation and Damage Development in Al/Al2O3/SiC Hybrid Metal Matrix Composite

Russian Journal of Non-Ferrous Metals - In this study, the micro-mechanisms involved in fatigue crack propagation are investigated qualitatively in a Al/Al2O3/SiC hybrid metal matrix composite...     

Correlation of Tribological Properties with Microstructure and Mechanical Properties of Graphite Cast Irons Centrifugally Cast for Engine Liner

This is a study of the influence of centrifugal process on the graphite morphology, mechanical and wear properties on flake graphite iron (FGI), spheroidal graphite iron (SGI) and compacted graphite iron (CGI). Melts of hypereutectic and almost of identical composition with or without melt treatment were centrifugally cast. The microstructure, mechanical and wear properties of these specimens were studied. In the microstructure for FG iron it has been observed that the centrifugal process produces flake size range class 2–3 (range 160–320 μm) and graphite of flake type A by about 67.9 % (field %) and combined flakes of type B, C, D and E will be of 32.1 % (field %). While SGI has been observed to have 96.1 % nodules and 330.0 nodules per square millimeter. Similarly CGI has been seen to produce 52.0 % nodules and 113 nodules per square millimeter. SGI possess the highest tensile strength, rupture strain and hardness of 604 N/mm², 6.1 %, 233 BHN respectively. Whereas FGI possess the least tensile strength, rupture strain and hardness of 303 N/mm², 0.65 %, 185 BHN respectively among the irons. CGI has a tensile strength, rupture strain and hardness of 369 N/mm², 1.2 % and 200 BHN respectively which lies in between those of FGI and SGI. During the wear test similar materials for both disk and pin combination show higher co-efficient of friction and wear rate than those for dissimilar material combinations. SGI disk and FGI pin combination show least wear. This combination would be ideally suited for engine liner and piston rings.     

离心铸造SiC颗粒增强铝基梯度功能复合材料薄壁筒状零件制备工艺研究

实验选用3种粒径为15μm、30μm和52μm的混合SiC颗粒制备铝基梯度功能复合材料,并采用半固态复合搅拌法制备浆料,制备出阶跃式变化的梯度功能复合零件毛坯,通过设计零件机械切削工艺,在毛坯的SiC颗粒偏聚层加工出璧厚2．5mm,高80mm的薄璧筒状零件。     

Wear Behavior of the Lead-Free Tin Bronze Matrix Composite Reinforced by Carbon Nanotubes

Copper-coated carbon nanotubes were prepared by the electroless plating route. The structure and component of copper/carbon tubes were characterized using a transmission electron microscope and energy dispersive spectrometer. The results show that the surface of the carbon tubes was covered by the copper particles. Copper/carbon tubes were used as the substitute of part of tin and all of lead in the tin bronze matrix, and the tribological properties of carbon nanotube-reinforced Cu-4 wt pct Sn-6 wt pct Zn composites were studied. The effects of the carbon nanotube volume fraction and sliding distance in unlubricated ball-on-disc wear test were investigated. The 3 vol pct carbon nanotube-reinforced Cu-4 wt pct Sn-6 wt pct Zn composite shows the Vickers hardness of 126.9, which is approximately 1.6 times higher than that of Cu-6 wt pct Sn-6 wt pct Zn-3 wt pct Pb tin bronze. The wear rate and average friction coefficients of 3 vol pct carbon nanotube-reinforced Cu-4 wt pct Sn-6 wt pct Zn composite were lower than those of the Cu-6 wt pct Sn-6 wt pct Zn-3 wt pct Pb tin bronze, respectively.     

Cu/Mo_5Si_(3p)复合材料的摩擦磨损性能研究

采用销—盘式摩擦磨损试验机研究了液相烧结制备Mo5Si3颗粒弥散强化铜合金在滑动干摩擦条件下的摩擦磨损行为。结果表明:Cu/Mo5Si3p复合材料具有优良的摩擦磨损性能。随着Mo5Si3含量的增加Cu/Mo5Si3p复合材料的硬度增加,摩擦系数和磨损失重量降低。Mo5Si3含量低时,Cu/Mo5Si3p复合材料的磨损机制为犁沟变形和粘着磨损为主,而Mo5Si3含量高时则为犁沟变形磨损为主。     

Investigation of Mechanical Properties and Dry Sliding Wear Behaviour of Squeeze Cast LM6 Aluminium Alloy Reinforced with Copper Coated Short Steel Fibers

LM6 aluminium alloy with 2.5–10 wt% of copper coated short steel fiber reinforced composites were prepared using squeeze casting process. Microstructure and mechanical properties viz., hardness, tensile strength and ductility were investigated. Dry sliding wear behaviour was tested by considering sliding distance and load. Fracture surface and worn surface were examined using field emission scanning electron microscope (FESEM). Hardness of composites increased with increasing wt% of fiber. Tensile strength of composites increased up to 19% for 5 wt% fiber composites. Further addition of fibers decreased the tensile strength of composites. Ductility of the composites decreased with the addition of fibers into the matrix. Wt% of fibers significantly decreased the weight loss, coefficient of friction and wear rate. Also the cumulative weight loss decreased up to 57% for 10 wt% of composites compared to LM6 aluminium alloy. Fracture surface of composite tensile specimen showed dimple formation and fiber pullout. Worn surface of matrix showed long continuous grooves due to local delamination on the surface. However, worn surface of composites showed fine and smooth grooves due to ploughing rather than local delamination. Copper coated steel fiber reinforcement in LM6 aluminium alloy exhibited better mechanical properties and wear resistance compared to matrix.     

Influence of Functionally Graded Material on Buckling of Skew Plates under Mechanical Loads

In this technical note, the critical buckling of simply supported functionally graded skew plate subjected to mechanical compressive loads is evaluated using first-order shear deformation theory in conjunction with the finite element approach. The material properties are assumed to vary in the thickness direction according to the power-law distribution in terms of volume fractions of the constituents. The effective material properties are estimated from the volume fractions and the properties of the constituents using the Mori–Tanaka homogenization method. The effects of aspect ratio, material gradient index, and skew angle on the critical buckling loads of functionally graded material plates are highlighted.     

熔铸-扩散法制备黄铜/钨铜功能梯度材料的研究

对用熔铸-扩散法制备的黄铜，钨铜功能梯度材料进行了研究，对界面区域的元素成分分布和微观组织结构进行了分析，对界面区域的电导率、结合强度及抗脉冲大电流损伤性能进行了测试。结果表明：用该法制备的黄铜，钨铜功能梯度材料，界面区域由成分和组织渐变的三层结构组成；电导率在界面区域呈渐变分布趋势，没有出现电导率突变现象；这种结构缓解了因热性能不匹配而造成的热应力，提高了黄铜与钨铜合金的结合强度；界面的抗脉冲大电流损伤性能良好。     

Wear Behavior and Mechanism of Spheroidal Graphite Cast Iron

Wear behavior and mechanism of spheroidal graphite cast iron were studied on a pin-on-disk elevated temperature wear tester. The phase and morphology of worn surfaces were examined by X-ray diffraction and scanning electron microscopy. Results show that with an increase of load, wear rate of spheroidal graphite cast iron gradually increases under low loads, rapidly increases or potentially increases under high loads; wear rate increases with increasing ambient temperature. At 25–200 °C, adhesive wear prevails; oxidative wear and adhesive wear coexist at 100 °C. As load surpasses 150 N at 100 °C, extrusive wear appears. The elevated-temperature wear of spheroidal graphite cast iron is a physical and chemical process including the following reactions: xFe + y/2O₂?Fe_xO_y, 2C + O₂?2CO and Fe_xOy + yCO?xFe+yCO₂. Hence, at 400 °C, the amount of graphite and tribo-oxides are substantially reduced because of reductive function of graphite. It can be suggested that wear-reduced effect of graphite and tribo-oxides is impaired.     

Tribological Behavior of SiC Particulate Reinforced AA5754 Matrix Composite Under Dry and Lubricated Conditions

The present work dealt with an investigation on tribological behavior of AA5754 matrix reinforced with 10 wt% SiC particles composite by using a pin on disc machine. Sliding tests were conducted under dry and oil lubricated conditions against hardened DIN 100Cr6/EN31 steel counter surface. Wear rates of the matrix alloy and the metal matrix composite (MMC) were measured over load of 100 N under a speed of 4.71 m/s. Detailed scanning electron, optical microscopy analyses were undertaken to clarify the effect of SiC particles on tribological behavior. SiC reinforced AA5754 alloy exhibited lower wear rate than unreinforced alloy.     

Preparation and Characterization of Cast Ferrous Metal Matrix Composites

TiC/SiC reinforced cast ferrous composites have been prepared by smelting red mud—30 pct charcoal briquettes in a 20-kg basic lined, single-phase direct arc furnace. Elements like silicon, aluminum, zirconium, and so on are also reduced from their respective oxides in the red mud and dissolved in the ferrous matrix. TiC/SiC particulates in the composite grow in a typical spiraling fashion.     

低合金耐磨铸钢的研究与应用

低合金耐磨铸钢因含有Ｃｒ、Ｍｏ等元素，且显微组织为马氏体或马氏体＋贝氏体，不仅强度、硬度远高于高锰钢，冲击韧性也接近于高锰钢。目前在大型水泥磨、煤磨上使用已显示出明显的优势，使用寿命比高锰钢提高１￣２倍，在很大程度上可取代高锰钢，具有广泛的应用前景。介绍了国内外在这一方面的研究与应用情况。