Cast Composites Research Articles

3D-printed PEEK-carbon fiber (CF) composites: Structure and thermal properties

CF-PEEK composites were manufactured by 3D-printing using a novel FDM methodology and customized printer and were compared with their cast counterparts. The characterization of composite thermal properties in the range 25–300 °C revealed that 3D-printed CF-PEEK composites manifest 25–30% lower thermal conductivity than cast composites. Short carbon fibers used for reinforcement showed orientation along the polymer flow both in cast and 3-D printed samples causing the anisotropy of thermal properties. The hierarchical nature of 3DP CF-PEEK porosity was observed by SEM imaging, which allowed the identification of large scale inter-layer gaps and cracks, and fine scale intra-layer defects that are likely to be induced by the thermal and mechanical gradients within the deposit that arise during fabrication. Purposeful lay-up of long continuous carbon yarns during 3D-printing opens a way to fabricate tailored mechanical parts with desired anisotropy of properties.

A Review on Secondary Process of Hot Extrusion on Aluminum Metal Matrix Composite

Metal matrix composites (MMCs) have made a lot attention in engineering materials due its significantly improved properties including high specific strength, specific modulus, damping capacity and good wear resistance compared to unreinforced alloys. Recent developments actives are carried on processing of Aluminum metal matrix composite Since in last few year lot of work is carried on AMC's. The present paper aims to summarize different processing methods and emphasis is given on effect of hot extrusion as a secondary process of aluminum Al6061 and stir casting processing technique. Extensive applications of cast composite has been found in automotive, aerospace field, Transportation and other engineering industries.

Effects of SiCp Content on the Microstructure and Mechanical Properties of SiCp/Mg-5Al-2Ca Composites

The Mg-5Al-2Ca alloys reinforced by 2vol%, 5vol% and 10vol% 5 μm SiCp were fabricated by stir casting. The cast composites were subject to hot extrusion. In the cast composites, addition of SiCp disturbs the network distribution of Al2Ca phase along grain boundaries. After extrusion, grains of the matrix are refined further and the Al2Ca phase break into particulates. Moreover, the Al2Ca phase and grain size can be further refined by the addition of SiCp. Compared with Mg-5Al-2Ca alloy, the addition of SiCp introduces obvious improvement of tensile yield strength (TYS) and work hardening rate, however, at the expense of elongation. Unlike the TYS, the ultimate tensile strength (UTS) of SiCp/Mg-5Al-2Ca composite does not change monotonously with increasing SiCp's content, and the highest UTS appears when the SiCp's volume fraction is 5%. The interfacial debonding between SiCp and Al2Ca phase and cracked particles are considered as the main crack source for SiCp/Mg-5Al-2Ca composite.

The Influence of Homogenization on the Elemental Distribution and Properties of Cu-10Ni-1Fe-1Mn Alloy Ingot

A set of Cu-10Ni-1Fe-1Mn alloys were prepared. Electromagnetic casting, DC casting ingot organization, properties and composition distribution of the alloy were studied using Optical Microscope (OM), Scanning Electron Microscopy (SEM), Energy spectrum analysis (EDS), Xray diffraction (XRD), Brinell Hardness Test, and electrochemical tests. The results suggested that homogenization of the Cu-10Ni-1Fe-1Mn alloy changed its properties and distribution of composition. The results also suggest that electromagnetic casting can refine casting organization, homogenize the composition of the alloy, and the casting mechanical performance is superior compared to those of DC casting. However, the composition between Dendritic branch and Dendrites was still not homogeneous. After 1 h of homogenization treatment at 950°C, the ingot composition distribution became more homogeneous, and its stiffness decreased. The tube prepared by squeezing the homogenized ingot, was soaked in 3.5% NaCl solution for 240 h, after which the tube blank surface remained a bright metal luster and XRD analysis indicated that a Cu2O protective film of high density covered the surface of the tube. The homogenization treatment significantly improved the corrosion resistant properties of the alloy tubes.

Hydrogen induced microstructure evolution of titanium matrix composites

The effect of melt hydrogenation on microstructure evolution of Ti-6Al-4V matrix composites was investigated in this study. Molten alloy was hydrogenated with a mixture of hydrogen and argon, and reinforced at 5% total volume fraction with a 1:1 mol ratio mixture of TiB and TiC particles. Microstructure of as cast composites showed hydrogen induced more TiB whiskers with higher length-diameter ratio (LDR), because hydrogen accelerated atomic diffusion and then increased growth rate of TiB whiskers. Hot compression results indicated hydrogen reduced peak flowing stress. Microstructure of as compressed composites indicated hydrogen encouraged decomposition of residual lamellas. Hydrogen eliminated most cracks and holes along the interface between ceramic particles and matrix. Compared with unhydrogenated composites, the original ceramic particles in hydrogenated composites were fragmented into smaller pieces after compression. Electron back-scattered diffraction and transmission electron microscopy results indicated hydrogen increased volume fraction of dynamic recrystallization (DRX). And hydrogen decreased the density of dislocations nearby the interface.

Dry Sliding Friction and Wear Behavior of AA7075-Si3N4 Composite

The present investigation is aimed at identifying the influence of Si3N4 reinforcement on the mechanical and tribological behavior of AA7075-Si3N4 composite. Five different composites of AA7075 aluminum alloy reinforced by silicon nitride particles have been fabricated by the stir casting route. The percentage of silicon nitride was varied from 0-8 wt%. The cast composites were tested for hardness, density and compression strength. Unidirectional friction and wear testing was carried out for all compositions under five different loading conditions (10 N, 20 N, 30 N, 40 N and 50 N) at a constant sliding speed of 1 m/s. SEM and EDS analysis was also carried out for worn surface analysis and elemental analysis of the composites. The hardness and compression strength of the composites exhibited an increasing trend with an increase in wt% of reinforcement in the base alloy, showing 20% improvement in hardness and around 50% improvement in compression strength for 8 wt% Si3N4 addition. The addition of Si3N4 particles led to an improvement in the wear resistance by 37% at low loads (10 N) and 61% at higher loads (50 N). The COF for all varied compositions at low load (10 N) and high load (50 N) ranges from 0.10 to 0.20 and 0.25 to 0.30 respectively. Moreover, the COF is observed to increase until 4 wt% and beyond it decreases. Microscopic studies of worn surfaces revealed a dominance of delamination wear at lower concentrations (0 wt% and 2 wt%) and ploughing at higher concentrations (6 wt% and 8 wt%). The developed composites exhibited better mechanical and anti-wear properties and could serve as potential candidates in sliding applications such as bearings, brake drums, gears, sprockets and brake rotors.

Spin-coating: A new approach for improving dispersion of cellulose nanocrystals and mechanical properties of poly (lactic acid) composites

This study systematically evaluated the influence of masterbatch preparation techniques, solvent casting and spin-coating methods, on composite properties. Composites were manufactured by combining CNCs masterbatches and PLA resin using twin screw extruder followed by injection molding. Different microscopy techniques were used to investigate the dispersion of CNCs in masterbatches and composites. Thermal, thermomechanical, and mechanical properties of composites were evaluated. Scanning electron microscopy (SEM) images showed superior dispersion of CNCs in spin-coated masterbatches compared to solvent cast masterbatches. At lower CNCs concentrations, both SEM and optical microscope images confirmed more uniform CNCs dispersion in spin-coated composites than solvent cast samples. Degree of crystallinity of PLA exhibited a major enhancement by 147% and 380% in solvent cast and spin-coated composites, respectively. Spin-coated composites with lower CNCs concentration exhibited a noticeable improvement in mechanical properties. However, lower thermal characteristics in spin-coated composites were observed, which could be attributed to the residual solvents in masterbatches.

Does Social Capital Make a Difference for Dalit Women Representatives in Local Self Governance?

Women’s participation in political processes is important to address gender inequality and strengthen democracy. In Indian context, to empower women and enable political participation, 73rd Constitutional Amendment Act (1992) was introduced. Subsequently, many women entered politics. Though widespread proxy is reported, still a small proportion engages effectively in governmental participation (Hust, 2002; Mathew, 2003; Palanithurai, 2001). Studies also find female Dalit-headed panchayats are more active (Jayshree, 2010; Kalaiselvi, 2012). As the cultural norms, traditions and patriarchy are rigid, the paper attempts to examine what helps the women to be functional? Does social networks differ? Is there a link between social capital, by way of associationalism, and capacity for self governance as suggested by Putnam (1993) in the Indian context? Social capital is understood through social networks and membership in associations. Thirty-eight elected representatives of Panchayati Raj Institutions of southern Tamil Nadu, south India was interviewed in depth. Active members prominently belong to Dalit community and the social network of the elected active members is larger in size, heterogeneous in terms of age, gender and caste composition, and they are anchors themselves. They are primarily embedded in a web of political, caste and self-help group associations and have access to all women police stations, cooperative societies and political parties through family ties. The elected representative’s mandatory membership in district Dalit federations provides safety-net in dealing with discrimination and atrocities while also intervening at the village-level panchayat. Dalit women who have the capacity to mobilize social capital emerge efficient in local self governance.

Effect of ECAP process on the Microstructure and Mechanical Properties of Al6061-Gr Composites

In the present study, Aluminium metal matrix composite with Al6061 matrix and Graphite (5-20µm) particulate reinforcement of varying composition (2-8wt.%) were prepared by stir casting technique. Significant improvement in tensile strength and ductility was noticed as the weight percent of Gr increases in as cast Al6061- Gr composites. The cast composites have been subjected to annealing treatment at a temperature of 400°C for 4 hours to homogenize the microstructure. The specimens have been prepared from these composites for Equal Channel Angular Pressing (ECAP). The ECAP process was carried out at room temperature using a die with channel angle of 120o and Bc route was adopted for successive passes. The effect of ECAP on the microstructure and mechanical properties of Al6061 –Gr composites were evaluated. After ECAP process, the sizes of the reinforcement particles are not changed but they were distributed uniformly in the matrix. In addition, a significant reduction in the grain size of the matrix alloy was observed. The hardness and tension tests were conducted at room temperature as per ASTM standards. The results are compared with the base Al6061 material and as cast Al6061-Gr composites. There is a significant improvement in the hardness and the Ultimate tensile strength of ECAP processed composites.

Optimization for Turning of Aluminium and Titanium Di Boride Cast Composites Using Response Surface Methodology

In present work an effort has been set up to orchestrate aluminum metal matrix composite to study its machining properties. Status of aluminum metal matrix composite was set up by reinforcing Titanium di boride (TiB2). The cast composite samples were carefully machined. The outcome of machining components like cutting speed, feed and depth of cut on surface roughness were explored through turning operation. For modeling and optimizes the impact on surface roughness for input parameters of aluminum metal composites, the Response Surface Methodology was utilized. The adequacy of numerical model was finished using ANOVA. The deliberate and anticipated qualities were sensibly close, which verify that the numerical model can be adequately used. Response surface curve lines were made for formative the greatest conditions for a basic surface roughness. The anticipated condition delineates that the feed is the key variable taken after by cutting speed controls the surface roughness. The surface roughness was begin to decrease with reduce the feed and lift the cutting speed and depth of cut

Investigation on Mechanical Behavior of Hot Rolled Al7075-TiB2 In-situ Metal Matrix Composite

This study focuses on microstructure and mechanical behavior of Al7075 based composites reinforced with Titanium Diboride by in-situ processing route. Cast alloy and composite were further hot rolled at a processing temperature of 450°C. A total reduction of 80% was achieved with four passes. Both cast and rolled matrix alloy and composite were characterized for its microstructure, microhardness and tensile behavior. Microstructure examination shows a good dispersion of TiB2 particles with excellent bond with matrix. After hot rolling, reinforced particles have oriented in the rolling direction. Hot rolled alloy and composite exhibited a considerable enhancement in the microhardness, strength and ductility

Synthesis and Study of Microstructure and Mechanical Properties of Cast Al1100 (Mg) - SiC Composites

Metal matrix composites (MMCs) is a innovative engineering materials in which a tough reinforcement is included into a metal matrix to improve its properties. MMCs are used for weight critical applications like aircraft engines and in the automotive industries. Among the various types of MMCs, particulate-reinforced composites are the most versatile and economical one. SiC particulate can be considered as ideal reinforcements due to their high strength, high aspect ratio and thermo-mechanical properties. The development of aluminium matrix composites is receiving considerable emphasis in meeting the requirements of various industries. The objective of this work is to reinforce Al 1100-Mg alloy with different wt% of SiC (0, 3, 6, 9 and 12) was added by melt stirring method for the same alloy and composites. Microstructural Studies using Scanning Electron Microscopy (SEM) and Mechanical property like hardness and tensile properties have been investigated for cast base alloy and composites.

Effect of sand concentration on erosive – corrosive wear behavior of chill cast aluminum – boron carbide composites

In the present investigation, the erosive – corrosive wear behavior of chill cast aluminum boron carbide composites have been studied in marine environment. The composites were fabricated by gravity die casting using vortex method. Metallic chill materials with different thermal conductivity (stainless steel, cast iron and copper) were used as mold materials. Silica sand of particle size 312 microns was used as erodent material. The experiments were performed at room temperature for a testing period of 3 hours at a speed of 900 rpm by varying the sand concentration from 10–50 wt. % in steps of 20 wt. %. From the present study it is noticed that, irrespective of the material the slurry erosive wear rate increases, as the quantity of the sand in the slurry increases. It is also noted that the copper chill cast composites exhibits greater wear resistance than the cast iron and stainless steel chill cast composites due to its fine grain structure obtained through faster cooling rate of the copper chill because of its high thermal conductivity. The study of the worn surface by scanning electron microscope reveals that the increase in the quantity of the sand in the slurry solution leads to greater damage to the exposed surface due to the rise in the extremity of the erosive – corrosive attack.

Effect of Angle of Impingement on Air Jet Erosion Wear Behavior of Chill Cast Aluminum-Boron Carbide Composites

In the present investigation, the effect of angle of impingement on the air jet erosion wear behavior of chill cast aluminum boron carbide composites have been studied under room temperature. Stir casting technique was employed for the development of the composites. Metallic materials like stainless steel, cast iron and copper with various thermal conductivities are used as end chills. The erodent material used was silica sand of 312 microns. All the tests were conducted with the erodent silica sand particles of grain size 312 µm at a standoff distance of 20 mm with a testing time of 5 minutes for 15°, 30°, 45° and 60° angles of impingement. The worn surface analysis was carried using scanning electron microscope to examine the mechanism of material removal process. From the obtained results, it is noticed that the weight loss of the samples increases with the increase in angle of impingement up to 45° and then decreases with further increase in the angle of impingement for a given standoff distance and testing time. However, for all the composite samples studied, the copper chill cast Al-B4C composites exhibit greater erosive wear resistance than the cast iron and stainless steel chill cast composites.

Novel preparation of Al-5%Cu / BN and Si3N4 composites with analyzing microstructure, thermal and mechanical properties

The purpose of this research is to develop and characterize composites of Al-5%Cu alloy reinforced by silicon and boron nitride (Si3N4, BN). The developing of this type of composites gives a new trend of metal matrix composite synthesizing, especially in the case of boron nitride. The stir cast composites showed large areas of porosity and agglomeration. On the other hand, the squeezed cast composites exhibited a fairly uniform particles distribution throughout the matrix alloy. The microstructure and XRD results of the composites confirmed a reaction occurred at the interface between the particles and alloy. AlN and AlB2 phases were identified in Al5%Cu-Si3N4 and Al5%Cu-BN composites respectively. The ageing results showed that the time to reach peak hardness decreased with addition of the particles. Also, the ageing kinetics was significantly accelerated due to the presence of BN particulates. The coefficient of thermal expansion (CTE) results of the matrix alloy and its composites were practically and theoretically determined. Difference between experimental and calculated values of CTE was less than 8%. Increasing the concentration of Si3N4 increased YS from 215MPa in the matrix alloy to 285MPa in the Al-5%Cu-7%Si3N4 composites at a testing temperature of 20°C.

Effect of fly ash particle reinfo rcement on microstructure, porosity and hardness in Al-(Si-Mg) cast composites

The microstructure of cast Al-4Si-Mg reinforcedwith fly ash particles at various particlecontents has been studied. The composites were fabricated by stir casting process andcharacterized by optical microscopy, image analyzer, scanning electron microscopy and hardness measurements. The results showed that particle contents affected to the presence oforosities and hardness of the composites. It was observed that increasing the fly ash contentincrease the porosity in the composites, with the matrix alloy reinforced with 15 wt.% of fly ash particles having the highest porosity and lowest hardness.

Fractographic and three body abrasion behaviour of Al-Garnet-C hybrid chill cast composites

Fractographic and tribological behaviour of hybrid composite of aluminum alloy LM13 matrix with garnet and carbon was investigated. Conventional stir casting technique was used to fabricate the composites with chill cast technique. Various chill materials like Copper, Steel, Iron and Silicon carbide were used to improve the directional solidification. The garnet being added ranges from 3 to 12 wt-% in steps of 3wt-% and constant 3wt-% of carbon. The experiment evaluates the mechanical, fractographic and three body abrasion behaviour of the hybrid composites for various parameters of load, garnet and chills. Microstructural characterization of the composite samples revealed a uniform distribution of reinforcements with minimum clustering. SEM was used for examine worn surfaces. The addition of garnet and carbon reinforcement decreases the wear rate of hybrid composites. Fracture behaviour showed the changes from ductile mode to brittle mode of failure. Further, directional chilling with copper chill improves the wear resistance of the composites.

Fabrication and Tribological Behavior of Stir Cast Mg/B4C Metal Matrix Composites

Magnesium-based metal matrix composites (MMMCs) have emerged as good alternative material to conventional materials due to their promising advanced properties. In the present work, magnesium-based metal matrix composites (MMMCs) reinforced with B4C particles were successfully fabricated by cost-effective conventional stir casting technique. MMMCs with an average particle size of 63 µm and different weight percent (wt pct) of B4C between 3 and 12 were fabricated. Wear tests were carried out using a pin-on-disk against a steel disk under dry sliding condition at loads that varied between 1 and 5 kg at fixed sliding velocity of 1 m/s. The wear data clearly showed that wear resistance of cast composites is better than that of unreinforced magnesium, which is attributed to dispersion hardening caused by carbide particles. An increase in wt pct of B4C showed the wear resistance and hardness to increase significantly. The wear rate and coefficient of friction increased with an increase in applied load. The SEM and EDS analysis of the worn surfaces delineated the dominant wear mechanisms to be abrasion, adhesion, and oxidation under the different sliding conditions. At lower loads, the wear mechanism transformed from severe abrasive wear in pure magnesium (Mg) to mild abrasion, slight delamination, and oxidation in the Mg/12 wt pct B4C fabricated composite. At higher loads, severe abrasion, adhesion, delamination, and oxidation were found to be the major wear mechanisms in pure Mg, whereas in the Mg/12 wt pct B4C fabricated composites the corresponding mechanisms were mild abrasion, mild adhesion, slight delamination, and oxidation.

A Comparative Study of Thermal Conductivity and Tribological Behavior of Squeeze Cast A359/AlN and A359/SiC Composites

A comparative study of thermal and wear behavior of squeeze cast A359 alloy and composites containing 5, 10 and 15 wt.% AlN and SiC particulates was investigated. It was pointed out that A359/AlN composites have a superior thermal conductivity as compared to A359 alloy or even to A359/SiC composites. Composites wear characteristics were achieved by pins-on-disk instrument over a load range of 20-60 N and a sliding speed of 2.75 m/s. Results showed that A359/AlN and A359/SiC composites exhibited higher wear resistance values compared to A359 alloy. Moreover, A359/AlN composites showed superior values of wear resistance than A359/SiC composites at relatively high loads. Friction coefficients and contact surface temperature for A359/AlN specimens decreased as AlN content increased, while they increased for A359/SiC. Investigations of worn surfaces revealed that A359/AlN composites were covered up by aluminum nitrides and iron oxides, which acted as smooth layers. However, A359/SiC composites were mainly covered only by iron oxides. The superior thermal conductivity and the significant wear resistance of the developed A359/AlN composites provided a high durable material suitable for industrial applications.

Nitrogen as an alloying element improving material properties of the high carbon cast steel for ball mill liner plates

This paper presents an experimental analysis, which was carried out to evaluate the addition of nitrogen as an element complementing a chemical composition used for such cast parts. It has been demonstrated that nitrogen is very advantageous in the process of austenitizing and quenching, improving the stability and homogeneity of the alloy structure. Plates used as a lining of rotary mills operating in cement plants are castings, which acquire their properties mainly through proper heat treatment. Together with an appropriate microstructure and chemical composition, correct heat treatment allow to improve the wear resistance and significantly reduce the abrasive corrosion. Extensive investigations enabled establishing an optimum nitrogen content in the chemical composition of thick-walled castings used in cement industry. Results of experiments, managed for the steel of ledeburate type containing 0.8–1.2% of carbon, have found that the optimal level of nitrogen is in the amount of 0.07–0.10%. The proposed modification helped to reduce the amount of an expensive chromium, increase the hardness of the material (by about 2 HRC to 4 HRC), and to achieve the uniform microstructure and hardness, which noticeably improved the lifetime of the rotary mills plates.