Synthesis of Magnesium Based Nano-composites

Magnesium based nanocomposites are new lightweight and high-performance materials for potential applications in automotive, aerospace, space, electronics, sports and biomedical sectors primarily due to their lower density when compared to aluminum-based materials and steels. Synthesis of magnesium-based materials is relatively challenging and accordingly this chapter explicitly provides an insight into various techniques hitherto devised/adopted by various researcher for synthesizing magnesium based nano-composites (MMNCs). Overall processing of MMNCs often includes combination of primary and secondary processing. Primary processing fundamentally leads to the initial formulation and creation of MMNC ingots by solid, semi-solid or liquid state processing routes. This is followed by secondary processing that includes plastic deformation or severe plastic deformation to alleviate inhomogeneity, clustering of particles and fabrication defects to enhance the properties of the MMNCs. This chapter provides an insight into different fabrication methodologies, their benefits and limitations for MMNCs

Magnesium-based nanocomposites: A review from mechanical, creep and fatigue properties

The addition of nanoscale additions to magnesium (Mg) based alloys can boost mechanical characteristics without noticeably decreasing ductility. Since Mg is the lightest structural material, the Mg-based nanocomposites (NCs) with improved mechanical properties are appealing materials for lightweight structural applications. In contrast to conventional Mg-based composites, the incorporation of nano-sized reinforcing particles noticeably boosts the strength of Mg-based nanocomposites without significantly reducing the formability. The present article reviews Mg-based metal matrix nanocomposites (MMNCs) with metallic and ceramic additions, fabricated via both solid-based (sintering and powder metallurgy) and liquid-based (disintegrated melt deposition) technologies. It also reviews strengthening models and mechanisms that have been proposed to explain the improved mechanical characteristics of Mg-based alloys and nanocomposites. Further, synergistic strengthening mechanisms in Mg matrix nanocomposites and the dominant equations for quantitatively predicting mechanical properties are provided. Furthermore, this study offers an overview of the creep and fatigue behavior of Mg-based alloys and nanocomposites using both traditional (uniaxial) and depth-sensing indentation techniques. The potential applications of magnesium-based alloys and nanocomposites are also surveyed

Melt processing and characterisation of lightweight metal composites reinforced by nanocarbon

Increasing the specific strength of lightweight structural metals such as magnesium, which has two-thirds the density of aluminium, has the potential to significantly widen their application and improve the system energy efficiency and performance across transport and defence industries. Reinforcing magnesium matrices with nano-sized particles to form metal matrix nanocomposites (MMNCs) has shown promise as a way of achieving an increase in specific properties, albeit without the traditionally associated decrease in ductility. This study manufactured and characterised magnesium-based MMNCs to investigate the impact of nanoparticle reinforcements on the mechanical properties of the composites, their microstructure and the theoretical models used for the potential strengthening mechanisms. Multi-walled carbon nanotubes (MWCNTs) can be considered as the ideal reinforcing nanoparticle due to their exceptional mechanical properties, geometry and low density, which can take full advantage of the proposed strengthening mechanisms that occur when nanoparticles are added to a metal matrix. MWCNTs are however notoriously difficult to be homogenously dispersed in a metal matrix and are poorly wetted by molten metal; therefore, nickel coated MWCNTs (NiCNTs) and silicon carbide nanoparticles are also investigated as a potential solution for wettability in this study. Magnesium alloy AZ91D was used as the metal matrix material and the MMNCs were made using metal melt-stirring combined with a nanoparticle pre-dispersion technique. Melt processing and casting techniques are favoured in component manufacturing processes due their scalability and cost-effectiveness. The melt stirring processing parameters such as casting temperature, stirring time and stirring speed were thoroughly examined and modified to successfully produce MMNC samples. The compression mechanical properties of the AZ91D-MWCNT composites showed no change for a range of MWCNT concentrations for the melt stirring processing parameters tested. Theoretical studies of nanoparticle dispersion and wettability combined with electron microscopy of the cross sections of the samples showed that the pre-dispersion and melt stirring processes were insufficient to homogenously disperse the MWCNTs in the metal matrix, therefore NiCNTs were utilised. Whilst no significant differences in compression mechanical properties were seen for the AZ91D-NiCNT samples, a 13% increase in hardness was achieved. An 11% and 20% increase in hardness was achieved for samples of AZ91D composites reinforced with equal concentration of silicon carbide nanoparticles and whiskers, respectively. The poor wettability of MWCNTs by AZ91D melt, apparent from SEM imaging of the composite fracture surfaces, suggested that in order to take advantage of the superior mechanical properties of MWCNTs, a coherent interface between the MWCNT and the Mg matrix is necessary. The nickel coating and silicon carbide nanoparticles, known to wet with molten magnesium, may have provided a coherent interface that resulted in the measured increase in hardness.Open Acces

Casting and Solidification of Light Alloys

Investigation of the effect of casting and crystallization on the structure and properties of the resulting light alloys and, in particular, research connected with detailed analysis of the microstructure of light alloys obtained using various external influences of ultrasonic, vibration, magnetic, and mechanical processing on the casting and crystallization are discussed. Research on the study of introduction of additives (modifiers, reinforcers, including nanosized ones, etc.) into the melt during the crystallization process, the technological properties of casting (fluidity, segregation, shrinkage, etc.), the structure and physicomechanical properties of light alloys are also included

In Situ Metal Matrix Nanocomposites: Towards Understanding Formation Mechanisms and Microstructural Control

Lightweight materials are critical to meet the ever-increasing demands for improved fuel economy in the automotive, aerospace and defense industries. Consequently, aluminum alloys have been employed extensively in these industries for structural applications owing to their high strength-to-weight ratio. However, Al alloys suffer from several shortcomings, such as poor thermal stability of mechanical properties, limiting their usage for components operating in elevated temperature environments. Recently, the incorporation of nano-scale particles in the Al matrix, termed metal matrix nanocomposites (MMNCs), has been identified as a promising approach to improved ambient and elevated temperature mechanical properties, while still retaining the lightweight benefits of Al. MMNCs manufactured through typical ex situ incorporation methods, wherein pre-made particles are mixed into the matrix, can suffer from precursor contamination and undesirable particle/matrix interfacial reactions, making incorporation and large-scale processing difficult. In situ processing alternatives, where particles are created directly in the melt via direct reaction, have been demonstrated to exhibit improved particle/matrix interface stability and easier incorporation within the matrix. However, the ability to reliably control critical mechanical property-dependent particle characteristics (i.e., particle size, volume fraction, and dispersion) remains a barrier to large-scale processing of in situ MMNCs. The research for this dissertation is aimed at elucidating the mechanisms governing formation of the particles and provide guidance to controlling the resulting microstructure of MMNCs processed via in situ methods, for the purposes of informing large-scale processing efforts. In this work, we investigate the processing-microstructure-mechanical property relationships for two in situ processing methods, namely: in situ gas-liquid reaction (ISGR) for Al-AlN MMNCs and thermite-assisted self-propagating high-temperature synthesis (SHS) for Al-TiC MMNCs. We find that the SHS process is more capable of readily producing nano-scale TiC particles in a wide variety of volume fractions and dispersions dependent on processing conditions. Additionally, we report on successful SHS processing, at our industry partner, of commercial pilot-scale quantities of in situ Al-TiC MMNCs exhibiting enhanced mechanical properties for relatively low amounts of particle addition. The preliminary results are a promising demonstration of the potential for commercial-scale processing of in situ MMNCs. Building upon our study of large-scale processing of MMNCs, we then perform a more detailed investigation into understanding the formation mechanisms and microstructural control of the thermite-assisted SHS process. By leveraging 2D and 3D microstructural quantification techniques with a thermodynamic-based analysis, we identify three potential direct- and indirect- reaction pathways governing TiC formation and the conditions under which they are active. We also demonstrate an approach for correlating processing-property relationships via multivariate statistical analysis (i.e., canonical correlation analysis (CCA)). Using CCA, we report on the dominant processing variables affecting final MMNC microstructure and particle characteristics and discuss the link between processing variables, reaction pathways, and resultant microstructural signatures. Our results and analysis are expected to inform a more rational approach to process control of in situ SHS MMNCs, as well as being applicable to other in situ processing methods.PHDMaterials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163192/1/reesecw_1.pd

Manufacturing methodology on casting-based aluminium matrix composites: systematic review

Ongoing industrial demand for lightweight materials has spiked the research interest in aluminium-based metal matrix composites for its specific properties. The amount of scientific publication available on the matter has led to the vast production of knowledge, which highlights the need for a systematic assessment if further progress is expected. In this paper, a systematic review of the published literature is conducted, according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, on the Scopus and Web of Science databases were used in the literature search, which was completed on the 29 August 2020. The data of the research work is structured in the particle pre-processing stage and the melt processing stage. The present review clarifies the combined pair-wise effect of particles and the melt treatment performed on their wettability or dispersive or de-agglomerative capability, which allows to achieve their final mechanical properties.This work was supported by PTDC/EMEEME/30967/2017 and NORTE-0145-FEDER030967, co-financed by the European Regional Development Fund (ERDF), through the Operational Programme for Competitiveness and Internationalization (COMPETE 2020), under Portugal 2020, and by the Fundação para a Ciência e a Tecnologia—FCT I.P. national funds. Also, this work was supported by Portuguese FCT, under the reference project UIDB/04436/2020, Stimulus of Scientific Employment Application CEECIND/03991/2017, research doctoral Grant 2020.08564.BD

Obtaining and Characterization of New Materials

At present, more and more procedures and technologies used to discover and characterize new materials are available, including advanced characterization techniques.This Special Issue covers a wide range of topics about obtaining and characterizing new materials, from the nano to macro scales, including for new alloys, ceramics, composites, biomaterials, and polymers and the procedures and technologies used to enhance their structure, properties, and functions. To select new materials for future use, we must first understand their structure and their characteristics using modern techniques such as microscopy (SEM, TEM, AFM, STM, etc.), spectroscopy (EDX, XRD, XRF, FTIR, XPS, etc.), and mechanical tests (tensile, hardness, elastic modulus, toughness, etc.) and their behaviors (in vitro and in vivo; corrosion; and thermal—DSC, STA, DMA, magnetic properties, and biocompatibility), among many others