Aykut Canakci

Effect of volume fraction and size of B4C particles on production and microstructure properties of B4C reinforced aluminium alloy composites

Abstract A stir casting process was developed to produce aluminium alloy composites containing two different sizes and volume fractions of B4C particles up to 10 vol.-%. Manufacturing of B4C particle reinforced 2024 aluminium alloy composites was modified so as to reduce the processing temperature. In the present study, in order to improve incorporation of the B4C particles by 2024 aluminium alloy melt, a novel pretreatment process before stir casting was attempted, and a significant improvement was gained. This finding showed that the treatment modified the surface condition of boron carbide powders via the removal of oxides. The comparison of added and incorporated particle ratios (the yield rate) indicated that the amount of incorporated particles decreased with increasing volume fraction and decreasing size of particles. Scanning electron microscopic observations of the microstructures revealed that the dispersion of the coarser sizes of particles was more uniform, while finer particles led to agglomeration of the particles and porosity. The results showed that the density of the composites decreased with increasing particle volume fraction and decreasing particle size, whereas the porosity and hardness values increased with increasing particle volume fraction and decreasing particle size.

Microstructure, electrical conductivity and hardness of multilayer graphene/Copper nanocomposites synthesized by flake powder metallurgy

In this study, the influence of multilayer graphene content on the green and sintered properties of the multilayer graphene/Copper nanocomposites was investigated. Flake powder metallurgy, as a new production method, was employed to prepare the multilayer graphene reinforced copper matrix nanocomposites. Results showed that the increase in agglomeration content inhibited particle-particle contact during the sintering process and therefore sintered density decreased with increasing the multilayer graphene content. The green density of 8.46 g/cm3 was found for the monolithic Cu sample, which was 16.4% higher than that of the 5 wt% MLG/Copper nanocomposites. The high conductivity value (78.5 IACs) was obtained with 0.5 wt% the multilayer graphene reinforced nanocomposites. The electrical conductivity of sintered 5 wt% the multilayer graphene/Copper nanocomposites was 61.48 IACs. When the amount of the multilayer graphene particles as higher than 3 wt%, the decreasing rate in hardness significantly increased. The decreasing rate in the hardness of the multilayer graphene/Copper nanocomposites can be attributed to decrease in density and the non-homogeneous distribution of multilayer graphene particulates in Cu matrix.

Effect of weight percentage and particle size of B4C reinforcement on physical and mechanical properties of powder metallurgy Al2024-B4C composites

In this study, Al2024-B4C composites containing 0, 5, 10 and 20 wt% of B4C particles with two different particle sizes (d50=49 μm and d50=5 μm) as reinforcement material were produced by a mechanical alloying method. Two new particle distribution models based on the size of reinforcement materials was developed. The microstructure of the Al2024-B4C composites was investigated using a scanning electron microscope. The effects of reinforcement particle size and weight percentage (wt%) on the physical and mechanical properties of the Al2024-B4C composites were determined by measuring the density, hardness and tensile strength values. The results showed that more homogenous dispersion of B4C powders was obtained in the Al2024 matrix using the mechanical alloying technique according to the conventional powder metallurgy method. Measurement of the density and hardness properties of the composites showed that density values decreased and hardness values increased with an increase in the weight fraction of reinforcement. Moreover, it was found that the effect of reinforcement size and reinforcement content (wt%) on the homogeneous distribution of B4C particles is as important as the effect of milling time.

Prediction of the influence of processing parameters on synthesis of Al2024-B4C composite powders in a planetary mill using an artificial neural network

Abstract In this study, an artificial neural network approach was employed to predict the effect of B4C size, B4C content, and milling time on the particle size and particle hardness of Al2024-B4C composite powders. Al2024-B4C powder mixtures with various reinforcement weight percentages (5%, 10%, and 20% B4C), reinforcement size (49 and 5 μm), and milling times (0–10 h) were prepared by mechanical alloying process. The properties of the composite powders were analyzed using a laser particle size analyzer for the particle size and a microhardness tester for the powder microhardness. The three input parameters in the proposed artificial neural network (ANN) were the reinforcement size, reinforcement ratio, and milling time. Particle size and particle hardness of the composite powders were the outputs obtained from the proposed ANN. The mean absolute percentage error for the predicted values did not exceed 4.289% for the best prediction model. This model can be used for predicting properties of Al2024-B4C composite powders produced with different reinforcement size, reinforcement ratio, and milling times.

Prediction of effect of volume fraction, compact pressure and milling time on properties of Al-Al2O3 MMCs using neural networks

An artificial neural network (ANN) model was developed to predict the effect of volume fraction, compact pressure and milling time on green density, sintered density and hardness of Al-Al2O3 metal matrix composites (MMCs). Al-Al2O3 powder mixtures with various reinforcement volume fractions of 5, 10, 15% Al2O3 and milling times (0 h to 7 h) were prepared by mechanical milling process and composite powders were compacted at various pressure (300, 500 and 700 MPa). The three input parameters in the proposed ANN were the volume fraction, compact pressure and duration of the milling process. Green density, sintered density and hardness of the composites were the outputs obtained from the proposed ANN. As a result of this study the ANN was found to be successful for predicting the green density, sintered density and hardness of Al-Al2O3 MMCs. The mean absolute percentage error for the predicted values didn’t exceed 5.53%. This model can be used for predicting Al-Al2O3 MMCs properties produced with different reinforcement volume fractions, compact pressures and milling times.

The effect of mechanical alloying on Al2O3 distribution and properties of Al2O3 particle reinforced Al-MMCs

Abstract The properties of particle-reinforced aluminum composites depend on the microstructure and evolved uniformity distribution of particles in the matrix. The distribution of Al2O3 particles in the matrix and microstructure properties of varying volume fraction of particles up to 15% Al2O3 particle-reinforced Al metal matrix composites produced by the mechanical alloying technique was investigated. Alloying was performed in a planetary ball mill using a milling time varying from 0 h to 7 h, a ball-to-powder ratio of 10:1, and a ball mill velocity of 400 rpm. The produced compositions were cold-pressed at 700 MPa with a single action and sintered at 600°C for 3 h under Argon gas atmosphere. The relative density (both pressed and sintered), porosity and hardness of composites were also examined. The results of mechanical alloying processing were investigated with scanning electron microscopy (SEM), X-ray diffraction and laser particle size analyzer. SEM observations showed that relatively homogeneous distribution of Al2O3 reinforcement in the matrix could be obtained by mechanical alloying after 5 h. Moreover, the variation in hardness of the composites with alumina volume fraction and milling time was observed to be a strong function of the work hardening mechanism.

Physical and mechanical properties of stir-casting processed AA2024/B4Cp composites

Abstract In this study, metal matrix composites of an aluminum alloy (AA2024) and B4C particles with volume fractions 3, 5, 7, and 10 vol% and with sizes 29 and 71 μm were produced using stir-casting technique. The effects of B4C particle content and size of boron carbide on the mechanical properties of the composites such as hardness, 0.2% yield strength, tensile strength, and fracture were investigated. Furthermore, the relation between particle content, microstructure, and particle distribution has been investigated. The hardness of the composites increased with increasing particle volume fraction and with decreasing particle size, although the tensile strength of the composites decreased with increasing particle volume fraction and with decreasing particle size. Scanning electron microscopic observations of the microstructures revealed that dispersion of the coarser sizes of B4C particles was more uniform while the finer particles led to agglomeration of the particles and porosity.

Microstructural characterization and mechanical properties of functionally graded Al2024/SiC composites prepared by powder metallurgy techniques

Abstract Al2024/SiC functionally graded materials (FGMs) with different numbers of graded layers and different amounts of SiC were fabricated successfully by powder metallurgy method and hot pressing process. The effects of increasing SiC content and number of layers of Al2024/SiC FGMs on the microstructure and mechanical properties of the composite were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) analyses indicated that Al and SiC were dominant components as well as others such as Al4C3, CuAl2, and CuMgAl2. A maximum bending strength of 1400 MPa was obtained for two-layered FGMs which contained 40% SiC (mass fraction) on top layer. A decrease in microhardness and changes in porosity were discussed in relation to the SiC content and the intermetallics formation. The results show that the increase in microhardness values and intermetallic formation play a major role on the improvement of mechanical properties of the composites.

New Coating Technique for Al–B4C Composite Coatings by Mechanical Milling and Composite Coating

Mechanical milling (MM) process as a novel technique for producing Al–B4C composite coatings on the surface of low carbon steel was investigated. The coating thickness, morphology, and cross-section microstructure of the composite coatings were analyzed with scanning electron microscopy (SEM). Also, Vickers microhardness and surface roughness of the coating layer were measured. It was found that a dense Al–B4C composite coating could deposit on the surface, particularly, if longer milling periods. The microstructure of Al–B4C composite coatings revealed that the distribution of B4C particles in the Al matrix was homogenous. Increasing milling time from 6 to 30 h resulted in increase of the microhardness values from 220 to 280 HV for the pre-interface layer (5 μm).

Microstructure and Abrasive Wear Behavior of CuSn10–Graphite Composites Produced by Powder Metallurgy

In this study, CuSn10 metal-matrix composites (MMCs) reinforced with 0, 1, 3, and 5 vol.% graphite particulates were fabricated by powder metallurgy. The microstructure, relative density, hardness, and abrasive wear behavior of the composites were investigated. The abrasive wear tests were conducted on unreinforced matrix and CuSn10–graphite composites using a pin-on-disk-type machine. The effects of sliding distance, applied load, graphite particle content, and abrasive grit sizes on the abrasive wear properties of the composites have been evaluated. The microstructure evolution of composites and the main wear mechanisms were identified using a scanning electron microscope and an energy-dispersive X-ray spectrometer (EDS). The density and hardness of the sintered CuSn10–graphite composites decreased with increasing graphite content. The abrasive wear resistance increased with increasing graphite content, but the abrasive wear resistance decreased with increasing sliding distance, applied load, and abrasive grit size. Moreover, the wear resistance of the composite was found to be considerably higher than that of the CuSn10 matrix alloy and increased with increasing graphite particle content.