Synthesis of FeCrCoNiCu high entropy alloy through mechanical alloying and spark plasma sintering processes

Nowadays, advanced aluminum matrix composites (AAMCs) are known as the dominant emerging materials employable in different industrial sectors. The reason behind the use of AAMCs originates from the urgent need for weight reduction as well as high efficiency in the automotive, agriculture, aerospace, mining, and electronic applications. This paper deeply reviewed several recent progresses of AMMCs in architecture designs and advanced manufacturing technologies to break through the limitations and promote the overall performance of the AMMCs. The discussion offers a deep understanding of specific issues mainly related to the well-known strength-ductility conflict. As a matter of fact, the dependency of the properties of materials on the microstructure (size dependent) and their components (e.g. high-performance nano reinforcements) could simultaneously provide high efficiency and a series of size-dependent effects. Designing tailored architectures (e.g. harmonic structure, hierarchical structure, multimodal distributions, layered architectures, network structure, gradient structures, heterogeneous laminated structures), known as most promising, provides new routes for attaining high-efficiency and mechanical properties optimization. It is worth noting that special distribution concept in architecture design is to be used carefully, as a homogenous distribution suggests all the reinforcements are distributed in the undifferentiated locations while inhomogeneous distribution stands for the selective distributed locations following certain regularities. These novel architecture designs could be achieved through applying the advanced manufacturing technologies (e.g. severe plastic deformation, additive manufacturing, and powder metallurgy-based technologies) with the potential to be used on a large scale by employing innovative techniques for the preparation, processing, and producing of AAMCs. This paper aims to correlate the most important factor namely size dependency (in the opinion of the authors) to mechanical properties in architectural designs in AMMCs, and should serve as a guide for research on AMMCs, to design target performance levels for applications to numerous and different industrial applications. 

Architectural design of advanced aluminum matrix composites: a review of recent developments

The thermo-mechanical behavior of nanosized Al2O3 particles reinforcing aluminum was analyzed in the present paper. The material was prepared by spark plasma sintering and friction stir welding. The thermal stresses affecting the composite behavior during welding were modeled through COMSOL MultiPhysics, and the results were validated by the analyses of the composites’ mechanical properties. The spark-plasma-sintered materials presented limited porosity, which was taken into account during the modeling phase. Both model and experiments revealed that higher heat input is related to better material mixing during welding and sound mechanical properties. Thermal stresses lead to residual stresses close to 300 MPa in the thermo-mechanically affected zone for processing conditions of 1900 RPM and 37 mm/min. This leads to an increase in hardness up to 72 HV.

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Effect of Porosity on the Thermo-Mechanical Behavior of Friction-Stir-Welded Spark-Plasma-Sintered Aluminum Matrix Composites with Bimodal Micro- and Nano-Sized Reinforcing Al2O3 Particles

Architecture dependent strengthening mechanisms in graphene/Al heterogeneous lamellar composites

Enhancement of mechanical properties of tungsten alloy via disordered microstructure and solid solution strengthening

Flake powder metallurgy (FPM) combined with micro/macro-rolling (MMR) was employed to fabricate Al2O3/Al laminated composites with high dislocations storage capability. The effect of deformation mode on the laminated ultrafine grain structure and on the dislocations density was analyzed. Additionally, a model based on microstructure and processing parameters is proposed to describe the effect of size, aspect ratio and crystallographic textures of the matrix grains on dislocation density. It was shown that the dislocation density depends on Al2O3 dispersion degree and Al2O3-Al interfacial bonding level. They are further driven by mechanical micro-rolling process, as well as grain refinement, crystallography texture, and high aspect ratio resulted from macro-rolling process. It was demonstrated that the MMR process provides the laminated ultra-fined grains (UFGs) with higher dislocation storage capability with respect to equiaxed grains. The described process provides a good coordination between the Al2O3 dispersion, Al2O3-Al interfacial bonding as well as crystallographic textures, size and shape of the matrix grains.

Microstructure dependent dislocation density evolution in micro-macro rolled Al2O3/Al laminated composite

Silicon nitride (Si3N4) coating was deposited on AISI D2 tool steel through employing duplex surface treatments—pack siliconizing followed by plasma nitriding. Pack cementation was performed at 650 °C, 800 °C, and 950 °C for 2 and 3 hours by using various mixtures to realize the silicon coating. X-ray diffraction analyses and scanning electron microscopy observations were employed for demonstrating the optimal process conditions leading to high coating adhesion, uniform thickness, and composition. The optimized conditions belonging to siliconizing were employed to produce samples to be further processed via plasma nitriding. This treatment was performed with a gas mixture of 75 pct H2-25 pct N2, at the temperature of 550 °C for 7 hours. The results showed that different nitride phases such as Si3N4-β, Si3N4-γ, Fe4N, and Fe3N can be recognized as coatings reinforcements. It was demonstrated that the described composite coating procedure allowed to obtain a remarkable increase in hardness (80 pct higher with respect to the substrate) and wear resistance (30 pct decrease of weight loss) of the tool steel.

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Characterization of Tribological and Mechanical Properties of the Si3N4 Coating Fabricated by Duplex Surface Treatment of Pack Siliconizing and Plasma Nitriding on AISI D2 Tool Steel

Behzad Sadeghi

Papers

Microstructure dependent dislocation density evolution in micro-macro rolled Al2O3/Al laminated composite

Characterization of Tribological and Mechanical Properties of the Si3N4 Coating Fabricated by Duplex Surface Treatment of Pack Siliconizing and Plasma Nitriding on AISI D2 Tool Steel