Anna J. Dolata

Fabrication of functionally graded composites using a homogenised low-frequency electromagnetic field

A characteristic feature of functionally graded materials is the continuous spatial change of their mechanical, thermal or electrical properties. Deliberate controlling of the spatial distribution of reinforcement in the metal matrix composite is one way of these materials. The article describes the theoretical basis and experimental verification of a new method using a homogenised low-frequency electromagnetic field to produce particle-reinforced metal matrix composites with a controlled distribution of reinforcement. The method developed allows for obtaining local reinforcement of the composite casting, analogous to radial centrifugal casting. The article describes the methodology for designing a casting system, which allows such control of the electromagnetic field distribution in the liquid casting, which makes it possible to obtain the desired reinforcement distribution. Experimental verification of the method developed was carried out using the example of a sleeve made of AlSi12CuMg alloy reinforced with SiC particles at the outer wall.

Hybrid Comopsites Shaped by Casting Methods

In the presented work two methods of casting: gravity casting and centrifugal casting have been described. The main aim of the study was development procedures for producing the AlSi / SiC+C hybrid composite. Composite suspensions with the same phase composition were cast into molds with different coefficients of thermal conductivity. This allowed to determine the influence of thermal conditions on the formation of the structure and distribution of particles in the matrix. In the paper the conditions of casting, macro-and microstructure and selected properties of the casts have been presented. The structure of components and cast composites was examined by light and electron microscope, applying properly made preparations.

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.

Interaction of Al-Si Alloys with SiC/C Ceramic Particles and their Influence on Microstructure of Composites

Interaction of Al-Si alloys with SiC/C ceramic particles and their influence on microstructure of composites was discussed. This article presents a significant effect of modifying additives introduced into liquid aluminium. As it was shown in the research, Mg and Sr modifiers improve wetting conditions in Al/SiCp+Cp systems, as well as influence the composite’s structure and the structure of the interface between the components. The microstructure observations were performed using light microscopy (OLYMPUS GX 71) and scanning electron microscopy (PHILIPS XL30). Moreover, local analyses of chemical compositions as well as chemical elements mapping were performed using an EDX module for microarea chemical analysis. Based on structural studies, it was found that chemical composition of the aluminium alloy and its modification are equally important parameters.

Structure of Aluminium Matrix Composite with Ceramic Preform Obtained by Centrifugal Infiltration Process

The paper presents the microstructure analyzing of composite with aluminium matrix containing porous Al2O3 preform. The AlSi12CuMgNi eutectic alloy have been modified by 1 wt% Mg and 0.03 wt% Sr additions. The magnesium to improve the wettability between matrix and ceramic reinforcement have been added. In turn 0.03 wt% strontium addition were used to changes the size and morphology of the Al-Si eutectic grains. The components and composite material obtained by the centrifugal infiltration process was characterized by means of light and scanning microscopy methods. The conducted investigations proved the large degree of infiltration of ceramic porous by the aluminium alloy and good connection in the boundary area.

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.

Structure and Functional Properties of Surface Layer Produced on Cast Aluminium Light Alloys by Appliance of Anodisation

The aim of the work is presents the influence of casting method and anodic treatment parameters on properties, thickness and structure of an anodic layer formed on aluminium casting alloys. Investigations were carried out on the laser profile measurement gauge MicroProf from company FRT, abrasive wear test was made with using ABR-8251 equipment delivered by TCD Teknologi ApS and microstructure investigations were made with using a light microscope equipped with an electronic camera configured with a computer on two casting aluminium alloys which both were founding by pressure die casting and gravity casting. The researches included analyse of the influence of chemical composition, geometry, roughness and abrasive wear resistant of anodic layer obtained on aluminium casts.Research limitations/implications Contributes to research on anodic layer for aluminium casting alloys. Practical implications Conducted investigations lay out the areas of later researches, especially in the direction of the possible, next optimization anodisation process of aluminium casting alloys, e.g. in the range of raising resistance on corrosion. Originality of this research was to describe the range of possible applications increases for example as materials on working building constructions, elements in electronics and construction parts in air and motorization industry in the aggressive environment.

The Correlation between the Surface Geometry of Tested Materials and the Shape of Lubricant Drop

In manufacturing of air compressors, piston engines and guides, lubricants are used to result in formation of a continuous oil film that separates the friction surfaces. The continuity of this film within the entire operating range of the friction pair, from starting to steady state, is the guarantee of proper operation. The surface geometry of friction elements plays significant role in maintaining continuity of the oil film. The widely used method for obtaining proper surface condition of the structural components of piston systems is the honing process. This method consists of shaping the microgeometry of the surface of friction pair elements by material removal processing methods (turning, grinding, laser processing) to prevent rapid spreading of lubricant, and thus to prevent breaking of the oil film. In case of Al-MMCs using for manufacturing the parts of machines working under friction with lubrication conditions the shaping of their working surface by honing is limited by the machining efficiency. The investigations on surface geometry of elements made of composites including ceramic reinforcement revealed that presence of reinforcement particles on the working surface bring the changes which can be used for shaping the correct oil film. The investigations presented in this article can be used for evaluation of lubricant propagation process on the composite material surface.

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.