G.V. Seretis

Effect of Graphene Nanoplatelets Fillers on Mechanical Properties and Microstructure of Cast Aluminum Matrix Composites

Recently, many studies on the production of graphite/graphene reinforced aluminum-matrix composites using different fabrication methods, such as powder or semi-powder method, have been performed. However, cast aluminum/graphite or aluminum/graphene composites have not been widely investigated and the research on this production method mainly focuses on 3D graphite particle reinforcements. In this study, the use of a 2D graphene structure, i.e. graphene nanoplatelets (GNPs), in the production of cast Al/GNP composites is investigated. Graphene nanoplatelets reinforced cast aluminum matrix composites were produced using aluminum alloy as matrix material and different graphene nanoplatelets contents. Specimens were cast into a heated rectangular steel mold, the temperature of which was 100°C. All specimens underwent tensile and bending tests as well as hardness measurements and microstructural investigation. Ultimate Tensile Strength (UTS) was considerably increased, simultaneously with a slight decrease of elongation at break, in the case of 0.1 wt% graphene nanoplatelets addition. Regarding bending performance, a slight increase was observed as well. The flexural behavior for 0.1 wt% graphene nanoplatelets addition was exactly the same with the matrix material. The graphene nanoplatelets content found to affect both the surface and the chemical composition of the interdendritic region. After 0.1 wt%, further increase of the wt% graphene nanoplatelets content lead to formation of aluminum carbides (Al4C3) at the grain boundaries, with a consequent drop on the mechanical performance of the Al/GNPs composite.

Effect of Stainless Steel Flakes Content on Mechanical Properties and Microstructure of Cast 96.66% Pure Aluminum

Stainless steel flakes-reinforced cast aluminum matrix composites were produced using aluminum alloy of 96.66% purity as matrix material and different steel flakes contents as reinforcements. Aluminum matrix specimens with no steel flakes fillers addition were also produced for performance comparison. All specimens were cast into a slightly heated rectangular quenched steel mold, the temperature of which was 35 °C. Both matrix aluminum specimens and aluminum matrix composite specimens underwent tensile and bending tests as well as hardness measurements and microstructural investigation. As observed through microstructural examination, the interdendritic regions do not seem to be affected by steel flakes addition on their at% chemical composition, which remains Al:Fe:Mn:Mg ; 92.28:3.75:2.96:1.01, but only on their size. An increase of the flexure strength of about 20% was achieved by steel flakes-reinforcement of the matrix aluminum. In the case of the highest wt% addition, groups of steel flakes of high directivity towards solidification kernels were observed. These steel flakes group formations resulted in an impressive hardness increase, performing as hard support elements.

A Multi-parameter Experimental and Statistical Analysis of Surface Texture in Turning of a New Aluminum Matrix Steel Particulate Composite

Metal matrix composites (MMCs) represent a new generation of engineering materials in which a strong reinforcement is incorporated into a metal matrix to improve its properties including specific strength, specific stiffness, wear resistance, corrosion resistance and elastic modulus. Aluminum matrix composites (AMCs), a specific type of MMCs, are rapidly replacing conventional materials in various engineering applications, especially in the aerospace and automobile industries due to their attractive properties. From the literature already published it is evident that the machining of AMCs is an important area of research, but only very few if any studies have been carried out using metal particles reinforced AMCs. A multi-parameter analysis of surface finish imparted by turning to a new L316 stainless steel flake-reinforced aluminum matrix composite is presented. Surface finish is investigated by examining a number of surface texture parameters. Spindle speed as well as feed rate was treated as the independent variables under a constant depth of cut whilst roughness parameters were considered as the responses under an L9 orthogonal array experimental design. ANOVA analysis was also conducted to study the effect of the two cutting variables on the surface texture responses.