Light Metal Matrix Research Articles

Effect of SiCp on the microstructure and tensile properties of the Mg–3Y magnesium alloy

Magnesium matrix composite is another competitive light metal matrix composite following aluminum matrix composite, with excellent application prospects in the aerospace and automotive fields. In this paper, the Mg - 3Y – xSiCp (x = 0, 1, 3, 5 wt%) composites are fabricated by stir casting with ultrasonic vibration followed by extrusion. The microstructure of the alloys is investigated by means of scanning electron microscopy (SEM) imaging and electron backscatter diffraction (EBSD) techniques. The results reveal that the composites have a finer grain size due to the particle promoted nucleation (PSN) mechanism. When the SiCp content is 3 wt%, the grain size is the smallest (0.76 μm), and the refinement rate is about 16.7%. Moreover, the addition of SiCp can inhibit the transformation from low-angle grain boundaries (LABGs) to high-angle grain boundaries (HABGs), thus hindering the dynamic recrystallization (DRX) of the alloy, which decreases from 55.7% to 15.4%. The reduction in the proportion of recrystallized grains in the composite leads to increasing the maximum intensity of the texture. In addition, the tensile properties and the strengthening mechanism of the alloys are investigated. The results show that the composites have higher ultimate tensile strength (UTS) and yield strength (YS) due to the combination of grain refinement and dislocation strengthening. When the SiCp content is 5 wt%, the UTS (291 MPa) and YS (283 MPa) increase by ∼12.7% and ∼17.1%, respectively, over the matrix alloy. However, the addition of SiCp causes more oxides and holes in the alloys, which leads to a fracture strain (δ) decrease in the composites.

Sustainable tribology for reliability and efficiency

This special issue includes a collection of papers presented at the International Tribology Research Symposium (ITRS) 2021, held from 8th to 10th December 2021 in a virtual mode with the Tribology for Sustainability and Reliability theme. It has been observed that the types of machinery and components are improving daily as per the requirements to fulfill human needs. Due to these requirements in human necessities, new tribological challenges have developed that affect the reliability and efficiency of machinery and engineering components. Furthermore, the governments have also implemented stringent rules and regulations on industries to reduce environmental pollution. Researchers have developed sustainable (green) lubricants, superlubricity concepts in many engineering components, and new methodologies for contact area reduction, such as self-lubricating coatings, surface texturing, and surface modification. Therefore, this editorial has explored tribological advances, and Triboinformatics approaches for achieving sustainability and reliability. The practical, sustainable tribological approaches for the well-being of the society highlighted in this editorial are 1. Sustainable lubrication, 2. Space tribology, 3. Triboinformatics, 4. Biotribology, 5. Additive manufacturing, 6. Light metal matrix composites, 7. Sustainable machining, 8. Electric vehicles. These sustainable tribological approaches deliberated by the plenary, keynote, and invited speakers and participants of ITRS 2021 are guidelines for future research directions of tribology.

Micro-Mechanical Investigation of Interfacial Debonding in Carbon Fiber-Reinforced Composites Using Extended Finite Element Method (XFEM) Approach.

The interface debonding in carbon fiber-reinforced polymers is analyzed and evaluated using the extended finite element method (XFEM). In order to accurately evaluate the bonding properties between fibers and matrix, different tests were carried out, including the multiple tests for different orientations to study longitudinal, transversal, and shear properties of unidirectional carbon fiber-reinforced composites. Extensive experimentation has been performed in all the different groups and categories with different dimensions and parameters in order to ascertain the values of strength and the prediction of the damage to the structure. The experimental and numerical comparison provided significant trends and data to evaluate the mechanical properties of the interface. The values of stiffness and strength are compared and validated. Development of Representative Volume Element (RVE) for progressive damage model to these damage phenomena has already been performed as a feasibility study for the model, though it is not included in this particular paper. The results of this research for all the experimental and numerical sets can serve as reliable data in the microsimulation of devices and sensitive parameters that include carbon fiber-reinforced light metal matrix composites and makes a better investigative model that contributes to various conditions. It further offers an investigation of the microscopic deformation mechanisms in the composites.

Properties of Mg-based metal matrix nanocomposites processed by high shear dispersion technique (HSDT) - a review

: Metal Matrix Nanocomposites (MMNCs) often show excellent properties compared to their non-reinforced alloys due to either the achieved grain refinement or Orowan strengthening. Especially in light metals such as aluminium and magnesium as the matrix has the potential to be significantly improved in relation to mechanical properties. Functionalisation can also be achieved in some cases. However, the challenge lies in the homogeneous distribution of the ceramic nanoparticles in the melt, if MMNCs are processed via melt metallurgical processes. The large surface area of the nanoparticles generates large van der Waals forces which have to be overcome. Furthermore, the wettability of the particles with molten metal is difficult. Additional forces can be applied by ultrasound, electromagnetic stirring or even high-shearing. In this paper properties of MMNCs with a light metal matrix will be presented, which were produced with the High-Shearing Dispersion Technique. First, the process with its different characteristics and the underlying theory is presented and then property improvements are discussed by comparing MMNCs to their matrix materials.

In Situ 3D-µ-Tomography on Particle-Reinforced Light Metal Matrix Composite Materials under Creep Conditions

In transportation light metal matrix composites (L-MMCs) are used increasingly due to their improved creep resistance even at higher application temperatures. Therefore, the creep behavior and failure mechanisms of creep loaded particle reinforced L-MMCs have been investigated intensively. Until now, creep damage analyses are usually performed ex situ by means of interrupted creep experiments. However, ex situ methods do not provide sufficient information about the evolution of creep damage. Hence, in situ synchrotron X-ray 3D-µ-tomography investigations were carried out enabling time and space resolved studies of the damage mechanisms in particle-reinforced titanium- and aluminum-based metal matrix composites (MMCs) during creep. The 3D-data were visualized and existing models were applied, specifying the phenomenology of the damage in the early and late creep stages. During the early stages of creep, the damage is determined by surface diffusion in the matrix or reinforcement fracture, both evolving proportionally to the macroscopic creep curve. In the late creep stages the damage mechanisms are quite different: In the Al-MMC, the identified mechanisms persist proportional to creep strain. In contrast, in the titanium-MMC, a changeover to the mechanism of dislocation creep evolving super-proportionally to creep strain occurs.

Mechanistic force modeling in drilling of SiCp/Al matrix composites considering a comprehensive abrasive particle model

SiCp/Al composite is one of the key light metal matrix composites widely used in aerospace and electronics industries due to its excellent material properties. Understanding the mechanism of abrasive particle action and the cutting force generation is crucial for achieving desired hole quality and machining accuracy. However, there is no research on cutting force modeling in drilling of SiCp/Al composites. This paper proposes an energy-based mechanistic modeling method to predict the cutting force in drilling of SiCp/Al composites for the first time. A new comprehensive abrasive particle model considering different particle action mechanisms, such as cracking, debonding, and squeezing, is presented to depict the energy consumed by abrasive particle action. Experiments with a wide range of particle volume fractions and feed rates, and different particle sizes were carried out to validate the accuracy of the proposed model. Results show that the proposed model can accurately predict the cutting force with an average error of 6.55% in drilling of SiCp/Al composites. Furthermore, the energy consumed on abrasive particle action is estimated to be 8.2–13.6% of total cutting energy. The proposed model on SiCp/Al composites can be extended to other particle reinforced metal matrix composites.

Analytical modeling of subsurface damage depth in machining of SiCp/Al composites

SiC particle reinforced aluminum matrix (SiCp/Al) composite has been one of the key light metal matrix composites, which is widely used in aerospace and electronics industries due to its excellent material properties. However, the abrasive particles within the materials easily lead to severe tool wear during machining, and the subsequent machining-induced subsurface damage (SSD) will significantly affect the fatigue properties of composite structures. In this paper, an analytical model considering the effects of reinforced particle, thermal-mechanical coupling, and tool wear is first proposed to predict the SSD depth during cutting of SiCp/Al composites. The two-body abrasion and three-body rolling mechanisms are introduced to describe the effects of the particles on the tool-chip interface friction. The mechanical stress and thermal stress induced by mechanical load and thermal load, respectively are simultaneously taken into account. Meanwhile, the tool wear is considered in modeling of friction characteristic of tool flank-workpiece. The SSD depth is evaluated as a measure of variation in microhardness along the depth normal to the cross-section of the machined surface. The correctness of the proposed model was validated by the orthogonal cutting experiments of SiCp/Al composites under different tool wear values and feed rates. A good agreement is found by comparing the predicted and experimental results, which proves that the proposed model can accurately predict the SSD depth with an error of 7.8% in average. Furthermore, the results indicate that even a new tool is used, the SSD depth can reach to hundred micros level during machining of SiCp/Al composites, which is significantly greater than homogeneous metal machining.

Micro-debond Experiment and Analytical Model for Interfacial Fracture Toughness between Single Carbon Fiber and TiO2 Micro-droplet

To improve mechanical behaviors of the carbon fiber-reinforced metal matrix composites, TiO2-coated carbon fibers are usually used in the composites to protect the fiber from degradation. Thus, it is crucial to maintain both strong interfacial bonding at carbon fiber–TiO2 interlayer interface and high interfacial fracture toughness, which influence the damage tolerance of the composites as well as their energy absorption capacity. In this study, different single carbon fiber/TiO2 systems with and without modified carbon fiber were prepared at heat treatment temperatures of 80 and 700 °C, respectively, and an analytical modeling for evaluating interfacial fracture toughness from the micro-debond tests by using the tests that record only the debond and friction force as a function of the TiO2 micro-droplet length was implemented first, and then, the interfacial adhesion forces, interfacial fracture toughness and the influence of friction force and thermal residual stress on the fracture toughness of the systems were discussed in detail. From the experimental and theoretical results, heat treatment temperature and local strong bonding sites have a significant effect on the interfacial fracture toughness, while the interfacial morphology and functional groups are dominant in determining the interfacial adhesion forces. Meanwhile, the dominant factor of the interfacial fracture toughness will change as the heat treatment temperature increases. The friction force is a major contributor to the interfacial fracture toughness of the systems treated under lower temperature (80 °C), while the residual thermal stress is responsible for the toughness of the systems treated under higher temperature (700 °C). The results in this study can serve as reliable input data in multi-scale simulation of the carbon fiber-reinforced light metal matrix composites and offer exciting opportunities for further investigation of the microscopic deformation mechanisms in the composites.

Production and Properties of Light Metal Matrix Nanocomposites

Metal matrix nanocomposites (MMNCs) with a light metal matrix are hybrid materials that have recently become the focus of interest for materials scientists and industry [...]

Optimization of wear performance on aluminium die cast A360-M1 master alloy using response surface method

Abstract Aluminium die cast A360-M1 master alloy with mass fraction (0.4 wt%) Al-5%Ti-1% B light metal matrix composite (LMMC) was prepared using the stir casting method. A three-level principle composite design test was developed using the boxbehnken response surface methodology. Variation in parameters such as load, sliding distance and sliding velocity were made in the range of 10–30 N, 500–1500 m, and 0.5–1.5 m/s respectively. Tribological dry sliding wear tests were performed as per the experimental design, using a pin-on disc setup at room temperature. Analysis of variance (ANOVA) was applied to study the impact of process parameters and their interactions viz., Load, sliding distance, sliding velocity on specific wear rate (SWR), frictional force (FF) and coefficient of friction (COF). The objective of this research is to recognize the parameters that significantly affect the output features such as specific wear rate, friction force, and COF of the aluminium die cast A360-M1 master alloy light metal matrix composites. Further, a mathematical model has been expressed by relating the boxbehnken response surface method in order to estimate the tribological characteristics. This work shows this A360-M1 master demonstrating the minimization of SWR, FF, and COF with response of load, sliding distance, and sliding velocity.

Current Research and Future Prospect on the Preparation and Architecture Design of Nanomaterials Reinforced Light Metal Matrix Composites

Current Research and Future Prospect on the Preparation and Architecture Design of Nanomaterials Reinforced Light Metal Matrix Composites

Improvement of the properties of light metal matrix Micro/Nanocomposite Materials: myth or reality?

The use of materials reinforced by micro-nanoparticles (MMC) is more and more widespread. According to recent studies, the addition of micro-particles in solid materials (polymers, concrete or metal alloys) gives them interesting properties in terms of thermal conductivity, electrical conductivity and mechanical resistance. These properties open new perspectives in terms of environmental consequences. They allow for example to lighten structures while improving their mechanical characteristics, to increase the performance of electrical conductors by reducing energy losses. We provide an example related to light metal alloys widely used in automotive industry and aeronautics. However, the introduction of particles presents several difficulties. The efficiency of particle addition at liquid state depends on many factors, like their dimension, the type of sedimentation forces and the chemical composition of both liquid alloys and particles:(i) at the metallurgical level, the particles are often very reactive and may modify the composition and the micro-structure of the alloy, which can be sometimes beneficial and sometimes damaging,(ii) in terms of scale-up and development of actual processes, the introduction of micro- and especially nanoparticles in liquid phase is a very difficult operation to achieve. Many types of devices are proposed but none is really satisfactory, especially regarding the homogeneity of the materials.We present some application cases related to magnesium alloys that perfectly illustrate the advantages and disadvantages of MMCs.

Development of Graphene Nanoplatelet-Reinforced AZ91 Magnesium Alloy by Solidification Processing

It is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites.

Residual stress induced mechanical property enhancement in steel encapsulated light metal matrix composites

Macro hybridized systems consisting of steel encapsulated metal matrix composites (MMCs) were produced with the goal of creating a low cost/light weight system with enhanced mechanical properties. The systems exhibit the high strength and modulus commonly expected from steels and high specific stiffness and low density observed in MMCs. The material combination also works to alleviate the high density of steels and the poor ductility of the MMCs. Furthermore, a coefficient of thermal expansion (CTE) mismatch induced residual compressive stress method is utilized to improve the ductility of the MMCs. Systems consisting of an A36 or 304 stainless steel shell with an Al-SiC or Al-Al2O3 shell are evaluated via neutron diffraction to quantify bulk residual stresses. The analysis shows variation in the measured strain due to steel thickness, difference in CTE between materials, and position within the composite. Improvements in ductility and yield stress are a result of these strains.

Aluminium AlSi12 alloy matrix composites reinforced by mullite porous preforms

The purpose of this work was to elaborate the method of manufacturing of composite materials based on porous mullite preforms infiltrated by AlSi12 aluminium alloy. The process of manufacturing the metal matrix composites by pressure infiltration is the subject of many scientific studies because it is characterized by high efficiency and allows for accurate mapping of elements of shape and surface of elements, while the structure and properties of the composites are determined by ceramic skeletons. The eutectic aluminium alloy AlSi12 was used as a matrix while as a reinforcement were used ceramic preforms fabricated by sintering of halloysite nanotubes (HNT) powder with an addition of carbon fibres as pore forming agents. The observations of the structure were made on the light microscope and in the scanning electron microscope. The developed technology of manufacturing of composite materials with the pore ceramic mullite infiltration ensures the expected structure and can be used in practice. The composite materials made by the developed method can find application as an alternative material for elements fabricated from light metal matrix composite material reinforced with ceramic fibrous preforms.

Insight into structural, mechanical and thermodynamic properties of zirconium boride from first-principles calculations

Density functional theory combined with quasi-harmonic Debye model is applied to research structural, mechanical and thermodynamic properties of zirconium boride (ZrB) with B1 structure. The structural properties of equilibrium are calculated and compared with other available experimental and theoretical data. The phonon dispersion curves and phonon density of states are calculated to prove the dynamical stability of the ZrB. The triaxial stress–strain relations of ZrB are obtained by increasing the strain of 0.01 each step until the structure collapses and the corresponding stress is treated as the ideal strength. According to the quasi-harmonic Debye model, the Debye temperature, heat capacity and thermal expansion coefficient under temperature of 0–1500K and pressure of 0–30GPa are deeply investigated. Particular attention is paid to discuss the rationality of ZrB used as the reinforcement for light metal matrix composites in this paper.

Thixoforming of High Melting Point Alloys

Although thixoforming complex near net shaped products in aluminium alloys is now an established technology in many automotive applications, current developments are taking place in a number of fronts: dynamic applications for load bearing components; alloy development - expanding the existing portfolio of thixoformable alloys; in materials recycling and in thixoforming of high melting point alloys. In the automotive industry, the drive for materials' development stems from the necessity of weight reduction in cars (more use of light alloys, including aluminium, magnesium, and metal matrix composites) and reduced costs. Most of the major automotive producers are currently using or are experimenting with thixoformed products. In Europe, Italian, French, German, and Spanish manufactures all have invested in the technology. In the United States, Ford is the main investor. The current manufacturing routes involve either 1) the use of non-dendritic alloy feedstock, which is cut to slugs of appropriate size before re-heating the slugs to the semi-solid state by a carousel of induction heaters and once the slugs have reached the required liquid fraction, robots automatically transfer them to the shot chamber of the thixoforming press (an adapted form of die-casting machine) to inject them into a die, or 2) cooling from the liquid to the semi-solid state before directly injecting into the die (New Rheocasing Method NRC). The production route is very similar to diecasting, however, the resulting properties of the parts are of much higher quality. Thixoforming has seen commercialisation around existing alloy composition based on aluminium-silicon 356 and 357 materials. A number of players are undertaking research to expand the portfolio of existing alloys, both in low 1) and high temperature alloys 2) . Current research in the later field is concentrating on the development of high melting point alloys such as steels, iron-alloys, copper-alloys, superalloys and other exotic materials, to further exploit the potential benefits of this under-utilised metal forming technique. However, although thixoforming of high melting point alloys offers exciting possibilities and tremendous potential, and has already been part of the original work of over thirty years ago, it is currently still in the research stage of development. This paper will concentrate on the later strand and will review past and current developments and offer insights to as yet unforeseen possibilities.

Magneto‐Acoustic Mixing Technology: A Novel Method of Processing Metal‐Matrix Nanocomposites

With increasing concerns regarding fossil fuel consumption and the implementation of widespread vehicle lightweighting, light metal matrix nanocomposites (MMNC) are seen as an attractive solution in many industrial sectors including transportation and aerospace, which demand materials that simultaneously possess high strength and low weight. [1–4] However, processing of MMNCs to evenly disperse nanoparticles remains one of the great challenges to the advancement of this technology. Herein, we present a novel method for MMNC fabrication: magneto-acoustic mixing technology (MAMT). This technology uses ohmically decoupled static and alternating magnetic fields to produce high-intensity, non-contact sonication suitable for melt processing. [5] In this study, MAMT is used to disperse dysprosium oxide (Dy2O3) nanorods (25 225 nm 2 ) and erbium oxide (Er2O3) nanospheres (50 nm) in magnesium (Mg) in a high energy density acoustic environment. The resulting materials exhibit novel microstructures influenced by both acoustic and magnetic effects, which combine to break up nanoparticle agglomerations and refine microstructures. As this is the first demonstration of this technology, the versatility of MAMT is highlighted, and its far-reaching impact will be discussed. Ceramic nanoparticle reinforcement of light metals has been extensively evaluated and shown to broadly improve mechanical properties such as strength, toughness, creep resistance, and elastic modulus. [6–8] While nanoparticle reinforcement is desirable, reliable incorporation has proven to be the fundamental challenge to MMNC production, as high surface energies drive particles to agglomerate. [6] When agglomerations are present in the fabricated microstructure, they act as crack nucleation sites, degrading material properties. [9] Melt dispersion methods like horn-based sonication, powder metallurgy, and spray forming have previously been used to disperse nanoparticles, but MAMT presents the opportunity to disperse nanoparticles using a non-contact, bulk processing technique. MAMT is distinct from other electromagnetic mixing, vibration or sonication technologies [10,11] because of its processing flexibility , deriving from the ohmically decoupled system. This facilitates independent control over many of the processing variables, enabling the production of alloys that do not suffer from many of the issues associated with more traditional melt processing technologies, such as contamination from melt-transducer interactions, [12] restricted geometries, and limited interaction volumes. [13]

Manufacture studies and impact behaviour of light metal matrix composites reinforced by steel wires

Magnesium alloys play an important role in the development of light metal matrix composites. Magnesium based metal matrix composites reinforced by particles and fibres (especially carbon fibres) are successfully applied in various fields of automotive and aircraft industry. Equally high potential in large-batch production regarding to relatively low price and high strength is expected from MMC with wires made of iron-based alloys. However, their application is hampered by the absence of intermetallic phase between iron and magnesium and low solubility of iron in magnesium.This paper makes a contribution to the investigation of the effect of steel wires surface preparation and of optimised production methods to improve the quality and type of adhesion with selected industrial magnesium alloys. The Fe/Mg-MMC specimens with steel wires reinforcement were manufactured by the help of advanced gas pressure infiltration method (GPI) in a graphite mould at Institute of Lightweight Engineering and Polymer Technology (ILK) of TU Dresden. For the examination of the obtained composites the computer tomography (CT), SEM microscopy with EDX, strength tests and fracture surface inspection has been used.

Morphology and Composition Controlled Synthesis of BN-Coated Aluminum Borate Nanowhiskers

Large quantities of BN-coated aluminum borate (Al18B4O33) nanowhiskers with typical 20 - 50 nm in diameter and 0.5 - 2 m in length have been successfully synthesized by sol-gel and post-thermal-treatment methods. The dependence of morphology and structures on the synthetic process of the coated nanowhiskers has been investigated systematically. Al4B2O9 nanowhiskers were first prepared at a relative low temperature, and then converted into Al18B4O33 nanowhiskers at higher temperatures in the air due to their high-temperature instability. Besides Al18B4O33phase, Al5BO9 and B2O3 could also be generated in the process of transition. However, if a flow of NH3 gas was introduced during the post-thermal-treatment of Al4B2O9 nanowhiskers, the Al5BO9 and B2O3 phases disappeared and BN-coated Al18B4O33 nanowhiskers were finally obtained. Uniform BN layers were coated on the surface of the nanowhiskers by the interfacial reaction between NH3 and B2O3 vapor which was in-situ generated from the nanowhiskers. The NH3-introducing temperature has a significant effect on the morphology and composition of the nanowhiskers. The BN-coated Al18B4O33nanowhiskers are envisaged to become prime candidates as reinforcement in light metal matrix composites.