Effect of Grain Size on the Properties of Aluminum Matrix Composites with Graphene

Abstract

The structure and mechanical properties of composites consisting of a metal matrix based on aluminum and its alloys of different compositions (AA-3003 and AA-5154) and graphene synthes sized in situ under a layer of molten salts were investigated depending on the chemical composition and grain size of the matrix. Aluminum matrix composites of three compositions were studied in as-cast coarse-grained, deformed fine-grained (grain size < 1 mm), and deformed sub microcrystalline (grain size < 1 μm) states in order to compare the structural characteristics of composites with different grain sizes. The composites were subjected to deformation with a split Hopkinson (Kolsky) bar and to dynamic-channel angular pressing. The hardness and dynamic mechanical properties of the composites were measured at strain rates ε˙ from 1.8 − 4.7 × 103 to 1.6 − 2.4 × 105 s−1. It was found that grain refinement induced a sharp increase in the hardness of composites with various compositions (by a factor of 1.6–2.6). A correlation of the elastic-plastic properties of the aluminum matrix composites with the grain sizes and chemical compositions of the matrices was established. A transition from coarse-grained to sub microcrystalline structure was shown to improve the elastic-plastic properties on average by a factor of 1.5. It was proved that the reinforcing effect of graphene increased with the decreasing grain size of the matrix. Mechanisms of reinforcement of the aluminum matrix composites using graphene were proposed.

Structure and Electrical Properties of AlFe Matrix Composites with Graphene

“…Composites based on Al-2.5%Fe alloy reinforced with 0.12% graphene were investigated. The synthesis of such aluminum-matrix composites was described in detail in [29][30][31][32] and involved the reaction of a molten Al-2.5% Fe alloy used as the matrix with a carbon-containing precursor under a layer of molten halide salts (sodium and potassium chlorides with the addition of ammonium fluorides). Molten salts were used as salt flux.…”

“…As shown in [29][30][31][32], one such technique is "in situ" synthesis in a molten metal matrix under a layer of molten salts. This method has been used to obtain metal matrix composites based on aluminum [29,30] and its alloys of different compositions (AA-3003 [31], AA-5154 [32]) and doped with 0.10-0.13 wt.% graphene.…”

“…As shown in [29][30][31][32], one such technique is "in situ" synthesis in a molten metal matrix under a layer of molten salts. This method has been used to obtain metal matrix composites based on aluminum [29,30] and its alloys of different compositions (AA-3003 [31], AA-5154 [32]) and doped with 0.10-0.13 wt.% graphene. Aluminum matrix composites have been studied in as-cast coarse-grained and in deformed-via-severe-plastic-deformation ultrafine-grained (grain size < 1 µm) states.…”

“…When an ultrafine-grain structure is formed in composites via high-strain-rate deformation, graphene nanoplatelets break up, bend, and primarily occupy the position along the grain-subgrain boundaries, providing an additional strengthening mechanism due to an interaction with the dislocations. The transition from a coarse-grained structure to an ultrafine-grained structure brings about a sharp increase in the hardness of the composites, namely, by a factor of 1.6 in the composites based on an Al-Mn alloy and by a factor of 2.6 in a AlGr composites [30].…”

Research progress on ceramic nanomaterials reinforced aluminum matrix nanocomposites

“…Strengthening mechanism of nanocomposite materials was thermal mismatch strengthening. Structure and properties of graphene incorporated aluminium or alloy nanocomposites are reported by Brodova et al [64]. Materials were synthesised in situ under a layer of molten salt.…”