Metal matrix nanocomposites (MMNCs) are thosemetal matrix composites where the reinforcement is of nanometer dimensions, typically less than 100nm in size. Also, it is possible to have both the matrix and reinforcement phases of nanometer dimensions. The improvement in mechanical properties of MMNCs is attributed to the size and strength of the reinforcement as well as to the fine grain size of the matrix. Spark plasma sintering has been used extensively over the past years to consolidate wide range of materials including nanocomposites and was shown to be effective noneconventional sintering method for obtaining fully dense materials with preserved nanostructure features. The objective of this work is to briefly present the spark plasma sintering process and review published work on spark-plasma-sintered metals and metal matrix nanocomposites.

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Spark plasma sintering of metals and metal matrix nanocomposites: a review

Effect of high energy ball milling on the morphology, microstructure and properties of nano-sized TiC particle-reinforced 6005A aluminium alloy matrix composite

Effect of high volume fraction of B4C particles on the microstructure and mechanical properties of aluminum alloy based composites

Mechanical alloying (MA) and mechanical milling (MM) techniques have been widely utilised over the past two decades for synthesis of various alloys and composites with equilibrium or metastable structure at room temperature.One of the most interesting features of MA/MM is the ability to produce nanocrystalline and amorphous materials. Several mechanisms for formation of nanocrystalline and amorphous structures have been introduced based on experimental findings and similarity of MA/MM to other solid-state processing routes. In this paper, the recent experimental observations reported on development of nanocrystalline and amorphous structures using ball mill technique are selectively examined and critically reviewed to provide further insight into the key issues related to this solid-state technique. The review includes four major parts. It begins with a brief introduction to MA/MM and the principles of ball milling process for synthesis of materials. The second part is devoted to the formation of ...

Application of mechanical alloying/milling for synthesis of nanocrystalline and amorphous materials

Effect of sintering temperature on microstructures and mechanical properties of spark plasma sintered nanocrystalline aluminum

In the present paper, the microstructure and mechanical properties of nanostructured Al–Mg–Si based AA6061 alloy obtained by high energy ball milling and spark plasma sintering were reported. Gas atomized microcrystalline powder of AA6061 alloy was ball milled under wet condition at room temperature to obtain nanocrystalline powder with grain size of ∼30 nm. The nanocrystalline powder was consolidated to fully dense compacts by spark plasma sintering (SPS) at 500 °C. The grain size after SPS consolidation was found to be ∼85 nm. The resultant SPS compacts exhibited microhardness of 190–200 HV 100 g , compressive strength of ∼800 MPa and strain to fracture of ∼15%.

Microstructure and mechanical properties of nanocrystalline high strength Al–Mg–Si (AA6061) alloy by high energy ball milling and spark plasma sintering

The present study focuses on optimization of operating parameters in wire electric discharge machining of AA2024 aluminium alloy reinforced with lithium and silicon nitride particles. Aluminium composite was produced through the two-step stir casting route with the combination of 2% lithium and 10% silicon nitride reinforcements. Experiments were performed using the Taguchi design of experiments to optimize the selected input parameters such as pulse on time, pulse off time, current and wire feed for the response parameter, material removal rate, and surface roughness. An ANOVA-based regression equation with genetic algorithm was used to optimize the input variables. The gray relational grade was also performed to optimize multiple performance characteristics. Taguchi-based optimization analysis results in wire feed as the domination factor for material removal rate and surface roughness. Increased wire feed increases the material removal rate with good surface finish as confirmed from gray relational grade analysis. Regression equation generated results with minimum error (<2%) proving the accuracy of the investigation. A genetic algorithm-based study also confirms the analysis of Taguchi and gray relational grade. The wire feed rate at 3 m/min and pulse on time of 120 microseconds were found to be similar for material removal rate and surface finish. Current at 50 A increases the material removal rate and current at 30 A results in good surface finish.

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Optimization of WEDM Process Parameters in Al2024-Li-Si3N4 MMC

Inorganic-based ceramic reinforcements are promising superior thermal behaviour and are lightweight and developed with aluminium alloy matrix for automobile applications. The AA6061 alloy nanocomposite containing 0 wt%, 4 wt%, 8 wt%, and 12 wt% of silicon nitride nanoparticles(50 nm) was synthesized by stir cast. The influences of thermal adsorption on silicon nitride (nano) additions, density, thermal response, hardness, and wear characteristics of AA6061 matrix nanocomposites are studied. Based on the rule of mixture, the density of nanocomposites is evaluated. The differential thermal and thermogravimetric analysis techniques are used to find the thermal response nanocomposite. The differential scanning calorimeter is used to find the heat flow between 400°C and 700°C. The micro Vickers hardness and wear characteristics of AA6061 nanocomposite were experimentally investigated by ASTM E384 and ASTM G99-05 standards. The adsorption of inorganic nanosilicon nitride particles (12 wt%) in AA6061 alloy showed a decreased mass loss with increased temperatures 0° to 700°C. The differential thermal analysis of nanocomposite reveals the transformation of solid-to-liquid phase under high temperature (528°C).

Inorganic Adsorption on Thermal Response and Wear Properties of Nanosilicon Nitride-Developed AA6061 Alloy Nanocomposite

ABSTRACT In the present study, nanocrystalline nickel (Ni) and nickel-chromium (Ni-Cr) alloy coatings were developed on copper (Cu) substrate using pulse current. The pulse current parameters include a cycle time of 240 milliseconds at a duty cycle of 0.5 and 4.17 Hz frequency. The surface morphology, texture, hardness, scratch resistance and porosity were investigated for different coatings developed by pulse plating. Energy Dispersive Spectroscopy (EDS) analysis revealed good quality Ni and Ni-Cr alloy coatings developed on the copper substrate. The peak current of the pulse has been observed to have an impact on the coating weight and thickness. The micrographs of the coatings explored under Field Emission Scanning Electron Microscopy (FESEM), depict uniform coatings consisting of fine primary and coarse secondary granules of Ni and Cr. The hard primary and secondary Ni granules deposited on the surface of Cu increase its hardness, corrosion and wear resistance. Further, it was observed that the Ni-Cr alloy plated samples are harder and less porous in nature compared to Ni plated samples.

K. Seetharama Raju

Papers

Microstructure and mechanical properties of nanocrystalline high strength Al–Mg–Si (AA6061) alloy by high energy ball milling and spark plasma sintering

Optimization of WEDM Process Parameters in Al2024-Li-Si3N4 MMC

Inorganic Adsorption on Thermal Response and Wear Properties of Nanosilicon Nitride-Developed AA6061 Alloy Nanocomposite

Investigation on the effect of nickel and nickel-chromium alloy pulse current plating on copper substrate