Graphene nanoplatelets (GNPs) exhibit ultra‐high strength and elastic modulus. Therefore, they are potential ideal reinforcements in metal–matrix composites (MMCs). In this work, we report the use of ...GNPs to strengthen the bulk Cu‐matrix composites. GNP reinforced Cu‐matrix (GNP/Cu) composites were prepared by a combination of the ball milling and hot‐pressing processing, and their mechanical properties were investigated. Microstructure studies indicated that the GNPs with 0–8 vol.% contents were well dispersed in the Cu matrix by ball milling. Compared to unreinforced Cu, the GNP/Cu composites showed a remarkable increase in yield strength and Young's modulus up to 114 and 37% at 8 vol.% GNP content, respectively. The extraordinary reinforcement is attributed to the homogeneous dispersion of GNPs and grain refinement. However, the mechanical improvement of GNP/Cu composites was still below the theoretical value. The possible reasons for this deviation were discussed and the methods for further mechanical improvement of GNP/Cu composites were proposed.
The aim of this Special Issue is to present the latest theoretical and experimental achievements concerning the mechanisms of microstructural change in metallic materials subject to different ...processing methods, and their effect on mechanical properties. It is my pleasure to present a series of compelling scientific papers written by scientists from the community of transition group metals, alloys, and intermetallic compounds.
TiAl/TiB2 in-situ metal matrix composites (MMCs) with greatly enhanced nanohardness are prepared via selective laser melting (SLM) for the first time in this study. The effect of TiB2 reinforcement ...on the microstructural characteristics, texture evolution and phase transformation of TiAl-based alloy is investigated. The results show that with increasing the TiB2 content, the average grain size gradually decreases, and the crystallographic orientation transforms from a strong (0001) direction to (101¯1) and (112¯1) directions. Meanwhile, TiB2 has a great effect on the texture of SLM-processed TiAl/TiB2 MMCs. With increasing the TiB2 content, more textured TiAl/TiB2 MMCs can be produced. The TiAl/TiB2 MMCs are dominated by α2 phase and small amounts of γ, B2, TiB2 and TiB phases are also detected. α2 phase contains the most important texture components of prismatic fiber with {101¯0}<112¯0> orientation, basal fiber with {0001}<112¯0> orientation and pyramidal fiber with {101¯1}<112¯0> and {112¯2}<112¯3> orientations. The TiB2 reinforcements are in the forms of the needlelike micro-TiB2 and irregular nano-TiB2 particles in the TiAl-based alloy matrix, and the nano-TiB2 particles are uniformly distributed with the size of 10 nm in length and 3–5 nm in width. The SLM-produced TiAl/TiB2 MMCs exhibit superior nanohardness of 10.57 ± 0.53 GPa, which is much higher than those of the traditional roll bonding fabricated TiB2 reinforced TiAl-based alloy. The findings would be a valuable reference for fabricating TiAl/TiB2 MMCs parts with controlled grain features, crystallographic texture and phase composition, enhanced mechanical properties and complex structures by SLM.
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In this contribution, authors present a review on the state-of-the-art in the utilization of industrial and agricultural waste materials for the development of metal–matrix composites (MMCs), ...providing, through the judicious analysis of an ample and varied references source – from the oldest to the newest ones – an insight into the challenges and opportunities for the exploitation to their full potential. In addition to its topicality, the novelty of this contribution lies in the presentation of key statistical, technical, and property-related information of a comprehensive variety of waste materials classed into two main groups, namely, fly ash reinforced MMCs and MMCs derived from other waste materials. Although fly ash has been exploited in a broad range of applications, the attention paid for its use in the development of MMCs seems to be insufficient. A purposely designed chart helped to pinpoint the more demanding and profitable applications of fly ash, and establish strategic opportunity areas. With the exception of the recent utilization of fly ash for the automotive industry, virtually no other waste material has been reused for a specific industrial application. In this context, by identifying five reasons for this observed delay, an essential goal of this review is to arouse the interest of academicians, scientists/technologists, and industrialists in the use of those materials for the fabrication of MMCs. In the case of agricultural materials, a twofold perspective may apply, because while on the one hand, certain chemical elements have to be removed for specific applications, on the other hand, recovery of certain elements might be more attractive. Based on the significant progress observed so far, in terms of scientific and technological research, a promising future can be anticipated. The proper use of industrial and agricultural waste materials entails knowledge generation as a prerequisite for incubation of pilot-plant and industrialization stages, culminating with all related benefits to society.
Rapid innovation in nanotechnology in recent years enabled development of advanced metal matrix nanocomposites for structural engineering and functional devices. Carbonous materials, such as ...graphite, carbon nanotubes (CNT's), and graphene possess unique electrical, mechanical, and thermal properties. Owe to their lubricious nature, these carbonous materials have attracted researchers to synthesize lightweight self-lubricating metal matrix nanocomposites with superior mechanical and tribological properties for several applications in automotive and aerospace industries. This review focuses on the recent development in mechanical and tribological behavior of self-lubricating metallic nanocomposites reinforced by carbonous nanomaterials such as CNT and graphene. The review includes development of self-lubricating nanocomposites, related issues in their processing, their characterization, and investigation of their tribological behavior. The results reveal that adding CNT and graphene to metals decreases both coefficient of friction and wear rate as well as increases the tensile strength. The mechanisms involved for the improved mechanical and tribological behavior is discussed.
A 1.0wt.% graphene reinforced aluminum 6061 (Al6061) composite was synthesized to investigate the effects of graphene dispersion by ball milling technique. The Al6061 powder and graphene were ball ...milled at different milling times. The composites were then synthesized by hot compaction in the semi-solid regime of the Al6061. A three point bending test was performed to characterize the mechanical properties of the composite. The ball milled powder and the fracture surfaces of the composites were analyzed using the scanning electron microscopy. A maximum enhancement of 47% in flexural strength was observed when compared with the reference Al6061 processed at the same condition.
Hybrid metal matrix composites (MMCs) exhibit superior overall mechanical and functional response when compared to their conventional counterparts and as a result have greater potential to be widely ...used for structural engineering and functional device applications. This review focuses on the recent developments in the fabrication techniques and properties characterization of Al, Mg, Ti, Cu, Fe/steel and Ni matrix composites containing hybrid reinforcements. The hybrid reinforcements are classified according to different types, shapes and sizes. Novel processing techniques proposed for achieving homogeneous distribution of hybrid reinforcements and forming special structures are critically reviewed. The mechanical properties of various matrix systems are summarized and analyzed, while the strengthening mechanisms triggered by hybrid reinforcements are discussed. Meanwhile, a prediction model for yield strength of hybrid MMCs is also proposed. The effects of hybrid reinforcements and fabrication conditions on functional properties, including tribological, thermal, and electrical properties, of the hybrid composites are also described systematically. Finally, future work for promoting further development of this field is also addressed.
•The hybrid reinforcements are classified and discussed in detail.•Novel processing techniques are critically reviewed.•The mechanical properties of various matrix systems are summarized and analyzed.•The strengthening mechanisms are discussed systematically.•Functional properties of the hybrid composites are also described systematically.
Due to a high propensity of nano-particles to agglomerate, making aluminium matrix composites with a uniform dispersion of the nano-particles using liquid routes is an exceptionally difficult task. ...In this study, an innovative approach was utilised to prevent agglomeration of nano-particle by encapsulating SiC nano-particles using graphene sheets during ball milling. Subsequently, the milled mixture was incorporated into A356 molten alloy using non-contact ultrasonic vibration method. Two different shapes for graphene sheets were characterised using HRTEM, including onion-like shells encapsulating SiC particles and disk-shaped graphene nanosheets. This resulted in 45% and 84% improvement in yield strength and tensile ductility, respectively. The former was ascribed to the Orowan strengthening mechanism, while the latter is due primarily to the fiber pull-out mechanism, brought about by the alteration of the solidification mechanism from particle pushing to particle engulfment during solidification as a consequence of high thermal conductive graphene sheets encapsulating SiC particles.
The necessity for high performance and low-cost materials caused the researchers worldwide to switch the focus from monolithic to composite materials. In the recent pasts, a significant effort has ...been made in this direction to fabricate numerous combinations of metal matrix composites. Among the MMCs, aluminum-based composites are treated as the most promising structural materials due to their high corrosion, wear resistance, specific modulus, and weight for automobile and aerospace applications. Aluminum MMCs were produced by various fabrication process after considering different reinforcement particles, such as borides, carbides, oxides, nitrides, and their combinations. Aluminum MMCs revealed excellent mechanical and wear characteristics owing to the formation of stable reinforcement particles in the composites. In the present review article, recent advances in processing, microstructure, wear, and mechanical characterization of aluminum composites reinforced with different particles are addressed. The future scope of these composites is also briefly discussed at the end of the manuscript.
In recent years, both industrial and academic world are focussing their attention toward the development of sustainable composites, reinforced with natural fibres. In particular, among the natural ...fibres (i.e. animal, vegetable or mineral) that can be used as reinforcement, the basalt ones represent the most interesting for their properties. The aim of this review is to illustrate the results of research on this topical subject. In the introduction, mechanical, thermal and chemical properties of basalt fibre have been reviewed. Moreover, its main manufacturing technologies have been described. Then, the effect of using this mineral fibre as reinforcement of different matrices as polymer (both thermoplastic and thermoset), metal and concrete has been presented. Furthermore, an overview on the application of this fibre in biodegradable matrix composites and in hybrid composites has been provided. Finally, the studies on the industrial applications of basalt fibre reinforced composites have been reviewed.
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