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Abstract- In recent times, light weight materials have always been an important topic in product design across several industries. The automotive industry has been paying attention to vehicle weight for decades since it has a direct impact on driving dynamics, agility, and fuel consumption. The automotive sector has benefitted by replacing steel (~7.8 g/cc) with lower density aluminum (~2.7 g/cc) parts for weight saving. Magnesium, being the lowest density (~1.74 g/cc) structural metal, provides further opportunities of reducing weight. This review presents an overview of a new material composed of magnesium matrix infused with a dense and even dispersal of ceramic silicon carbide nano particles to make automobiles fuel economic and of reduced weight. Magnesium is the lightest structural metal and it can replace aluminium in existing applications for further weight savings. Silicon carbide is an ultra-hard ceramic commonly used in industrial cutting blades. Infusing a large number of silicon carbide nano particles smaller than 100 nm into magnesium adds significant strength, stiffness, plasticity and durability under high temperatures. This presentation can guide future work and set goals that need to be achieved through material selection and will conclude with a cost-benefit perspective for typical light-metal applications in the automotive industry.
Introduction- Over the last few decades, the auto companies are putting a lot of effort into reducing weight. One of the main reasons automakers want to reduce weight is because it's a great way to increase MPG numbers. Aluminum matrix composites have been widely studied in the published literature for interest in replacing steel based structures with these lighter materials [1–3]. In recent years aluminum matrix composites have found numerous applications in automotive, aviation, and consumer products [4,5]. The automotive sector has benefitted by replacing steel (~7.8 g/cc) with lower density aluminum (~2.7 g/cc) parts for weight saving. Magnesium, being the lowest density (~1.74 g/cc) structural metal, provides further opportunities of reducing weight.
Magnesium matrix- Magnesium is a chemical element with symbol Mg and atomic number 12. Magnesium is the ninth most abundant element in the universe, eighth most abundant element in the Earth's crust and the fourth most common element in the Earth (below iron, oxygen and silicon), making up 13% of the planet's mass. Magnesium matrix composites are potential materials for various applications of aerospace and defence organisations due to their low density, good mechanical and physical prop- erties. The improvement of specific strength, stiffness, damping behaviour, wear behaviour, creep and fatigue properties are significantly influenced by the addition of reinforcing elements into the metallic matrix compared with the conventional engineering materials. In particular, Magnesium and its alloys have gained widespread attention in scientific research as well as commercial application as energy conservation and performance demands are increasing because of their low density, approximately two-third of that of aluminium, and high specific strength as compared to other structural metals. These properties are important in automotive and aerospace applications in order to reduce fuel consumption and to reduce green house emission.
Silicon carbide nano particles- Silicon carbide is composed of tetrahedra of carbon and silicon atoms with strong bonds in the crystal lattice. This produces a very hard and strong material. Silicon carbide is not attacked by any acids or alkalis or molten salts up to 800°C. In air, SiC forms a protective silicon oxide coating at 1200°C and is able to be used up to 1600°C. The high thermal conductivity coupled with low thermal expansion and high strength give this material exceptional thermal shock resistant qualities. Silicon carbide ceramics with little or no grain boundary impurities maintain their strength to very high temperatures, approaching 1600°C with no strength loss. Chemical purity, resistance to chemical attack at temperature, and strength retention at high temperatures has made this material very popular as wafer tray supports and paddles in semiconductor furnaces.
Grain structure of composite- The grain structure in SiC particle reinforced, as cast and heat treated magnesium matrix composites were investigated using analytical electron microscopy. No extensive chemical reactions were noticed between the magnesium and SiC particles. However, most of the eutectic phase appeared to nucleate at the surface of SiC particles. As with the aluminium based composite, precipitation was observed to take place on the dislocations, and dense precipitation was found to occur in the stress fields around the SiC particles. Examination of the fracture surface indicated that the bonding between SiC/eutectic is stronger than the bonding between SiC/magnesium matrix. Intergranular cracks have been observed both in the fracture surface and also in the polished and etched section. The fracture surface tends to exhibit more brittle morphology in the composite than in the alloy.
Mechanical properties- Infusing about 14% silicon carbide nanoparticles (<100 nm) into a molten magnesium-zinc alloy added significant strength, stiffness, plasticity, and durability at high temperatures.To create the composite, the researchers found a new way to disperse and stabilize nanoparticles in molten metals. They also developed a scalable manufacturing method that could pave the way for more high-performance lightweight metals. Potential applications include aerospace, cars, electronics, and biomedical devices.It's been proposed that nanoparticles could really enhance the strength of metals without damaging their plasticity, especially light metals like magnesium, but no one has been able to disperse ceramic nanoparticles in molten metals until now. With an infusion of physics and materials processing, our method paves a new way to enhance the performance of many different kinds of metals by evenly infusing dense nanoparticles.Ceramic particles have long been considered as a potential way to make metals stronger. However, with microscale ceramic particles, the infusion process results in a loss of plasticity.Nanoscale particles, by contrast, can enhance strength while maintaining or even improving plasticity. But nanoscale ceramic particles tend to clump together rather than dispersing evenly, due to the tendency of small particles to attract one other.To counteract this issue, researchers dispersed the particles into a molten magnesium -zinc alloy. The nanoparticle dispersion relies on the kinetic energy in the particles' movement. This stabilizes the dispersion and prevents clumping. To further enhance the composite's strength, the researchers used a technique called high-pressure torsion to compress it.
Weight reduction Vs fuel efficiency- The automotive industry has been paying attention to vehicle weight for decades since it has a direct impact on driving dynamics, agility, and fuel consumption. Due to the high cost of potential lightweight solutions and consumers’ limited willingness to pay for weight reduction in automotive, the use of costly lightweight materials has so far been limited. The introduction of CO2 emissions targets and correlated penalties, however, has reignited the conversation with an even stronger focus on weight reduction as a lever to minimize fuel consumption. The trend of ever-increasing weight for cars has been curtailed in recent years through the increased use of plastics (e.g., for fenders and recently doors in the new smart) and improved steel alloys (e.g., for the chassis).
Cast iron engine parts can be replaced with lighter weight (typically aluminum) parts, including:
Heads.
Intake manifold.
Flywheel.
Crank, rods, and pistons.
Aluminum water pump.
Lightweight mini-starter.
Cylinder Block
Engine efficiency in a conventional vehicle is more sensitive to a reduction in vehicle mass than any of the other power trains studied. s a rapid decrease in average engine cycle efficiency for the conventional vehicle. As the vehicle mass is reduced and the drive train size remains fixed, the engine operating point will shift in the map to lower torques, where the engine is less efficient.
Ramp-up of Mg SiC in automotive - Magnesium, which is the lowest density structural metal, has been considered as a viable option to address the aforementioned issues such as weight reduction and fuel efficiency in automotive structures. Magnesium alloy wheels, engine blocks, and body panels have been tested by various manufacturers. Magnesium based automotive components are now available as standard components or aftermarket parts used for customization. Lightweight alloy wheels are a prominent example of application of magnesium in the automotive sector. High cost of magnesium has limited the current automotive applications only to high end cars such as Porsche, BMW, Jaguar and Corvette. Engine blocks of magnesium alloys have been used in several models of these makes. Race cars have now over 50 years of history of using magnesium alloys in auto body and engine blocks for weight reduction. Development of low cost processing methods and wider use of these alloys is expected to lower the cost and result in self-accelerated growth of this sector. Now there is also interest in replacing existing materials used in thermal management components with magnesium alloys and composites.
Aviation- In aviation, lightweight materials (such as light metals, aluminum, plastics, and composites) already make up roughly 80 percent of all materials – significantly ahead of all other industries. The use of lightweight materials in aviation has two main drivers: the need to reduce fuel consumption and related costs and the wish to increase passenger/cargo load per flight. While steel played a very prominent role in the early years of aviation, it has been rapidly replaced by lighter materials. Aluminum is currently the most important lightweight material in aviation (about 50 percent) – mainly used in structural parts. Mg SiC composites, if used in this fields, will create a giant leap.
Wind industry- In the wind industry, extreme lightweight materials are applied in the long rotating blades, which transform the wind energy into rotating energy that is then transformed into electricity. Due to the high wind speeds and the size (length and mass) of the blades, the blade material has to bear high stress, which can be reduced by using extremely light materials. The majority of wind turbine manufacturers currently use glass fiber as structural material for their blades. This purpose can also be served well by Mg SiC composite.
Conclusion- Available studies on magnesium matrix composites are reviewed in this work. Rapidly increasing interest in magnesium matrix composites, due to their low density, is fueling interest in research and product development. A critical review shows that the understanding of microstructural aspects of magnesium alloys and their composites is well developed now but the mechanical properties are not widely available. Most available studies have characterized up to three compositions of magnesium alloy matrix SiC composites. In these composites the parameters such as particle density, wall thickness and sometimes, even the weight fraction, are not reported. In the absence of such detailed data, the development of theoretical models is not keeping pace with the experimental work