Maciej Dyzia

AlSi7Mg/SiC and Heterophase SiCP+CG Composite for Use in Cylinder-Piston System of Air Compressor

The article presents the results of the first phase of research on the development of manufacturing composites by pilot-scale technology. Producing of composite suspension in sufficient quantity to obtain approximately 50 casting pistons in one production cycle was the aim of this study. This allowed to assess the stability of the composite suspension manufacturing process and above all stability the casting process. Composite suspension (AlSi7Mg/SiCp and heterophase SiCp+Cg ) were prepared in one technological cycle including refining and modification of the alloy matrix, the introduction of ceramic particles and the homogenization of the suspension under reduced pressure. Objective of this study was to determine the basic parameters of the suspension of the manufacturing process, such as metal refining period, the rate of particles introduction and time of homogenization. In addition, as a evaluation criterion of quality the manufactured composite material accepted the possibility of pre-cast piston machining.

Microstructure of WE43 Magnesium Matrix Composite Reinforced Ceramic Particles

Magnesium alloys containing yttrium and neodymium are known to have high specific strength, good creep and corrosion resistance up to 523 K. The addition of ceramic particles strengthens the metal matrix composite resulting in better wear and creep resistance while maintaining good machinability. In the present study, WE43 magnesium matrix composite reinforced with SiC and carbon particulates were fabricated by stir casting. The microstructure of the composite was investigated by optical microscopy, quantitative metallography, scanning electron microscope and XRD analysis. Microstructure characterization of WE43 MMC showed inhomogeneous reinforcement distribution and presence of shrinkage porosity. Reinforcing particles are well bonded with the matrix, however, in some cases thin reaction layers was detected. The presence of SiC particles assisted in improving hardness.

Fabrication of Ceramic-Metal Composites with Percolation of Phases Using GPI

Al2O3/AlSi12CuMgNi composites were fabricated using gas-pressure infiltration (T=700°C, p=4 MPa) of an aluminium alloy into alumina performs. Volume fraction of the ceramic phase was up to 30%, while the pore sizes of the ceramic preforms varied from 300 to 1000 µm. Ceramic preforms were formed by method of copying the cellular structure of the polymer matrix. The results of the X-ray tomography proved very good infiltration of the pores by the aluminium alloy. Residual porosity is approximately 1 vol%. Image analysis has been used to evaluate the specific surface fraction of the interphase boundaries (Sv). The presented results of the studies show the effect of the surface fraction of the interphase boundaries of ceramic-metal on the composite compressive strength, hardness and Young’s modulus. The composites microstructure was studied using scanning electron microscopy (SEM). SEM investigations proved that the pores are almost fully filled by the aluminium alloy. The obtained microstructure with percolation of ceramic and metal phases gives the composites high mechanical properties together with the ability to absorb the strain energy. Compression tests for the obtained composites were carried out and Young’s modulus was measured by the application of the DIC (Digital Image Correlation) method. Moreover, Brinell hardness tests were performed. Gas-pressure infiltration (GPI) allowed to fabricate composites with high compressive strength and stiffness.

Influence of Particles Type and Shape on the Corrosion Resistance of Aluminium Hybrid Composites

AMCs due to good thermal and tribological properties, they are applied as the material for: pistons in modern combustion engines, drive shafts, shock absorber cylinders and brake nodes. Heavy-duty operation, especially under tribological conditions, frequently in corrosive environment, requires knowledge on their corrosion resistance. This paper presents the initial results of the research on susceptibility of aluminium alloy matrix composite material reinforced by SiC particles and mixture of SiC+C particles to corrosion. The purpose of the research was to determine the influence of reinforcing phases, their type and shape on corrosion behaviour in a typical corrosion environment, with low NaCl concentration, in relation to the matrix alloy. Determination of corrosion resistance of Al/SiC+C hybrid composite is a new issue and falls within the field of interest of the authors of this article.

Machinability of Aluminium Matrix Composites

The todays interest in MMCp results from a number of their creative properties, which can be designed through a proper selection of reinforcing components and technological parameters. The composite machine elements such us engine, compressor parts obtained by casting methods require the specially final machining. The introduction of hard ceramic particles increase wear resistance of composite material compared to unreinforcement alloy. Simultaneously increase wear and reducing the durability of tools cutting. The presence of ceramic particles (SiC, Cs) in aluminium matrix influence on surface geometry formed in track of processing. In this paper the results of investigations of geometry surface of composite after machining will be presented. Applied machining conditions for composite material were the same as for unreinforcement alloy, it made possible to compare the conditions of machining processing. It the piston skirt was conducted light profilometry investigation were the parameters 2D and 3D surface topography evaluated. Results shows dependency of surface parameters (Ra, Rz) after machining on kind, size and volume fraction of reinforcement particles applied in composite material.

TEM Investigations of Aluminium Composite Materials Reinforced with Ti(C,N) Ceramic Particles

Investigations of composite materials based on EN AW-AlCu4Mg1 (A) aluminium alloy reinforced with Ti (C,N) particles with weight ratios of 5, 10, and 15% are presented in this paper. The metallographic investigations of composite materials show banding of the reinforcing particles in aluminium matrix after the performed extrusion process. The structure observed in composites materials is oriented parallel to the extrusion direction. The amount of reinforcement particles Ti (C,N) has influence on the mechanical properties of the obtained composite materials. The increase of hardness is observed with the growth of the amount of reinforcement particles. Hardness increased from 89 HV1 for the material without the reinforcing phase to 143 HV1 for 15% of the Ti (C,N) reinforced material.Based on the microstructural investigations of the obtained composite materials, the uniform distribution of the reinforcing particles in the aluminium matrix was also revealed in the obtained structure.

Fine Particle Reinforced Composites Obtained by Suspension Method

In the production of composites by the suspension method (mechanical stirring) may beused, ceramic particles, which are wetted by the liquid metal such SiC, Al2O3 or glassy carbon.However, to obtain a stable suspension with the use a particle size below 10 μm is extremelydifficult. Phenomena related i.a. with agglomeration of particles, convection currents over moltenmetal surface make practically impossible to obtain composite material. One possibility to obtainfine reinforced composite is the use of in situ methods, in which the reinforcing phase is formed bythe reaction between the aluminum and the reactive powder oxides such FeO, TiO2, SiO2, NiO, Nb2O5 or Fe2O3. Such reactions are exothermic (aluminothermic) and their kinetics dependent onthe dispersion of the reactants, the quantitative phase composition and temperature.The technological solution involving the formation of a suspension with particles (chemically activewith aluminum) is one of the promising solutions to obtain batch material for the synthesis ofcomposites reinforced with Al2O3 and intermetallic phases. The aim of this study is to evaluate thesuitability of suspension technology to obtained in situ fine reinforced composite.

Course of Solidification Process of AlMMC – Comparison of Computer Simulations and Experimental Casting

The aim of the paper is to present the possibilities of computational simulations for the casting of aluminum matrix composite (AlMMC) reinforced with ceramics based on experimental data. The comparison of simulation and experimental results concerned the solidification process i.e. the course of solidification, temperature distribution and final arrangement of reinforcement particles. First, we have performed the experimental gravity casting of the aluminum matrix alloy AK12 (AlSi12CuNiMg2) and the composites AK12/SiC and AK12/Cg reinforced with silicon carbide SiC and glass carbon Cg, respectively, into the sand mold. During the experiment we have recorded the temperature using the ThermaCAM photometer system as well as in the selected point inside the sand mold. Using experimental data we have carried out the numerical calculations according to the methods and procedures contained in the program ANSYS Fluent 13. We have based the simulations on the two-dimensional model in which the Volume of Fluid (VOF) and enthalpy methods have been applied. The former is to describe two-phase system (air-composite matrix free surface, volume fraction of particular continuous phase) and the latter shows modeling of the solidification process of the alloy and composite matrix. We have used the Discrete Phase Model (DPM) to depict the presence of reinforcement particles. The assumption of the appropriate values of simulation parameters has shown that the simulation results are convergent with experimental ones. We have observed a similar course of the composite solidification (temperature change at the designated point), the temperature distribution and the arrangement of reinforcement particles for the simulation and experiment.