LM13 Alloy Research Articles

Aluminum boron carbide metal matrix composites for fatigue-based applications: A comprehensive review

Metal matrix composites (MMCs), known for their low density and superior stiffness, have gained significant attention in various load bearing and fatigue-prone applications. These composites offer distinct advantages over traditional monolithic metals, including enhanced mechanical and tribological properties, making them prime candidates for lightweight structural applications. Among ceramic reinforcements, boron carbide stands out due to its lower density, high elastic modulus, excellent refractoriness, and superior hardness, positioning it as an ideal reinforcement material. This review delves into the processing techniques, material properties, and microstructural characteristics of boron carbide-reinforced MMCs, with a focus on aluminum LM6 alloy as the matrix. Additionally, the paper explores the latest advancements and emerging opportunities for employing these composites in fatigue-critical applications, highlighting their potential to revolutionize industries requiring high performance and durability under repeated loading conditions.

Effective reduction of iron impurities in recycled aluminium-silicon alloy type LM-6 through sedimentation and filtration with synthesized Mn, Cr and Zr transition metal powders

Abstract In secondary aluminium recycling, impurity reduction, especially of iron, is a significant challenge as it deteriorates the material quality in the aluminium melt. Recycled aluminium alloys are widely used in various industries, including automotive, marine, and structural engineering. Specifically, LM-6 aluminium alloy is commonly used in automotive engine parts and transmission cases. This research focused on reducing the excessive iron content in LM-6 alloy scrap. Elements like manganese (Mn), chromium (Cr) and zirconium (Zr) were added to the melt in form of synthesized powders to form intermetallic compounds. These powders will also act as grain refiners, neutralizers and reducing the detrimental effects on the alloys. The powders were synthesized using the ball milling method with a ball to powder ratio of (5:1) to enhance mixing and amalgamation with the melt. The melt was held at an optimized temperature of 640 ± 10 °C to promote the formation of intermetallic sludge, encouraging the sedimentation of aluminium-iron (Al-Fe) intermetallic phases. XRD confirmed the formation of AlMn, AlCr, AlZr with other phases. After sedimentation, a glass fabric mesh with a pore size of 200 μm was used to effectively filter out β-iron during the filtration process. This technique reduced iron impurity in the melt by 50%–60%. As a result, the mechanical properties of the recycled aluminium improved significantly: hardness increased by 14%, and tensile strength increased by 36%. The wear and corrosion resistance of the material also improved due to the incorporation of the synthesized powders. SEM analysis revealed the plate-like formation of iron structures and confirmed the presence of the manganese, chromium, and zirconium powders in the metallographic analysis.

Investigation on mechanical properties of aluminum hybrid matrix composites reinforced with fly ash and titanium diboride using stir casting technique

Aluminium hybrid matrix composites (AHMCs) is employed in the automotive and aerospace industries because to their high strength-to-weight ratio, corrosion resistance, and tribological properties. The objective of this research is to examine the metallurgical, mechanical, and corrosion characteristics of Aluminum hybrid matrix composites (AHMCs) produced by reinforcing LM25 alloy with 5% fly ash and varying percentages (4%, 8%, 12%) of TiB2 using the stir casting technique. The uniform distribution of reinforcing particles was verified by capturing images via SEM and EDAX. Density, Tensile strength, microhardness was conducted for the prepared AHMCs. The outcome reported there was an enhancement by adding reinforcement particles of fly ash and TiB2 comparing to the pure LM25 alloy. This improvement was attributed to the presence of fly ash and TiB2 particles, resulting in a higher dislocation density, with increasing TiB2 content demonstrating improved strength and ductility compared to conventional LM25 alloy.

Impact of Aging Time on the Metallurgical Properties and Hardness Characteristics of an Al-Si-Mg-Cr Hypoeutectic Alloy Intended for Automotive Applications

This research investigates the microstructural evolution and mechanical properties of LM25 (Al-Si-Mg) alloy and Cr-modified LM25-Cr (Al-Si-Mg-Cr) alloy. Microstructural analysis reveals distinctive ε-Si phase morphologies, with Cr addition refining dendritic structures and reducing secondary dendrite arm spacing in the as-cast condition. Cr modification results in smaller-sized grains and a modified ε-Si phase, enhancing nucleation sites and reducing ε-Si size. Microhardness studies demonstrate significant increases in hardness for both alloys after solutionising and aging treatments. Cr-enriched alloy exhibits superior hardness due to solid solution strengthening, and prolonged aging further influences ε-Si particle size and distribution. The concurrent rise in microhardness, attributed to refined dendritic structures and unique ε-Si morphology, underscores the crucial role of Cr modification in tailoring the mechanical properties of aluminium alloys for specific applications.

Wear debris analysis of Al-Si/MWCNT nanocomposite during dry sliding wear tests

This study demonstrates the enhancement of wear resistance achieved by incorporating multi-walled carbon nanotubes (MWCNTs) in LM6 aluminum alloy to form nanocomposites. Experiments on wear resistance study were performed at different test parameters for various compositions of MWCNT in LM6 alloy. The size and nature of debris obtained post experiments were significantly dependent on the MWCNT contents. Wear resistance was found to increase with increase in the MWCNT fraction in the nanocomposite. The worn surface and the shape as well as the size of the debris were studied under scanning electron microscopy (SEM). Energy-dispersive spectroscopy (EDS) analysis of the worn surfaces was used to detect and measure the constituents present in the debris. SEM micrographs of the nanocomposites show that the features of the wear debris are completely altered when MWCNT was added. Further the wear mechanism underwent a change from oxidative in LM6 to that of ploughing in LM6 nanocomposite. The recorded surface roughness values also confirm the above findings and show significantly reduced surface roughness (∼82%, 0.75 wt% MWCNT). These results clearly demonstrate the advantage of addition of MWCNT for enhancing resistance to wear in LM6 alloys.

A Detailed Study on using Novel LM 25 Aluminium Alloy Hybrid Metal Matrix Nanocomposite for Nuclear Applications.

This article describes the use of graphite(Gr) and boron carbide (B4C) as multiple nanoparticle reinforcements in LM25 aluminum alloy. Because boron carbide naturally absorbs neutron radiation, aluminium alloy reinforced with boron carbide metal matrix composite has gained interest in nuclear shielding applications. The primary goal of the endeavor is to create composite materials with high wear resistance, high microhardness, and high ultimate tensile strength for use in nuclear applications. Science and Technology have brought a vast change to human life. The human burden has been minimized by the use of innovation in developing new and innovative technologies. To improve the quality of human life, fresh, lightweight, and creative materials are being used, which play a vital role in science and technology and reduce the human workload. Composite materials made of metal are being used because they are lightweight. Neutron absorption, high ultimate strength, high wear resistance, high microhardness, high thermal and electrical conductivity, high vacuum environmental resistance, and low coefficient of thermal expansion under static and dynamic conditions are all demands for the hybrid metal matrix composites utilized in nuclear applications. • Stir casting is used to create the novel LM 25 aluminum alloy/graphite and boron carbide hybrid nanocomposites. • The mechanical properties such as ultimate tensile strength, yield strength, percentage of elongation, microhardness, and wear behavior are calculated. • Three analyses are performed: microstructure, worn surface analysis, and fracture analysis of the tensile specimen. • Stir casting process< • Tensile, Hardness, Wear Test • Materials Characterization - FESEM, Optical Microscopy, EDS< Results: The mechanical properties values are 308.76 MPa, 293.51 MPa, 7.8, 169.2 VHN, and 0.01854mm3/m intended for ultimate tensile strength, yield strength, percentage of elongation, microhardness, and wear behavior, respectively. This implies that the synthesized composite may be used in nuclear applications successfully. The subsequent explanation was drawn from this investigative work: • The LM 25/B4C/Gr hybrid nanocomposite was successfully manufactured by employing the stir casting technique. For nuclear shielding applications, these composites were prepared with three different weight percentages of nanoparticle reinforcements in 2,4,6% Boron carbide and constant 4 wt.% graphite. • The microhardness values of the three-hybrid nanocomposite fabricated castings were determined to be 143.4VHN, 156.7VHN, and 169.2VHN, respectively. • The hybrid nano composite's microstructure revealed that the underlying LM 25 aluminum alloy matrix's finegrained, evenly dispersed nanoparticles of graphite and boron carbide were present.<br></br> • The microtensile test was carried out and it was found that the ultimate tensile strength, yield strength and percentage of elongation values are 281.35MPa, 296.52MPa, 308.76MPa, 269.43, 274.69, 293.51 and 3.4, 5.7, 7.8 respectively.<br></br> • Deformation caused the hybrid LM 25/B4C/Gr nanocomposite to fracture in ductile mode. Dimples and cavities are seen in the fracture because of the nanoparticle reinforcements and the matrix's tight connection.<br></br> • The wear loss of nanocomposite based on the input parameter applied load, sliding velocity and sliding distance values are 0.02456, 0.02189, 0.01854, 0.02892, 0.02586, 0.02315 and 0.02682, 0.02254, 0.02015 mm3/m, respectively.<br></br> • The LM 25 alloy's elemental analysis displays the aluminum alloy phase as the largest peak and the remaining elements as smaller peaks; also, the spectral analysis reveals the presence of boron (B), graphite (C), silicon, and ferrous in the aluminum alloy LM 25.<br></br> • Through worn surface FESEM investigation, it was shown that under sliding and high load situations, debris, delamination, and groove develop. Further rupture, fine, and continuous grooves were seen when low stress and sliding circumstances were applied to the LM 25/B4C/Gr and stir cast specimen. This result implies the presence of mild adhesive and delamination wear processes.</P>.

An Investigation of the Thermal Properties of LM13- Quartz- Fly-Ash Hybrid Composites

In the present work, a metal–matrix composite was casted using the LM13 aluminum alloy, which is most widely used for casting automotive components. Such applications require materials to withstand high operating temperatures and perform reliably without compromising their properties. In this regard, particulate-reinforced composites have gained widespread adaptability. The particulate reinforcements used comprise of one of the widely available industrial by-products. which is fly ash, along with the abundantly available quartz. Hybrid composites are fabricated through the economical liquid route that is widely used in mass production. Though there are numerous published research articles investigating the mechanical properties of metal–matrix composites, very few investigated the thermal properties of the composites. In the present work, thermal properties such as thermal conductivity and thermal diffusivity of cast hybrid composites were evaluated. The particulate reinforcements were added in varied weight percentages to the molten LM13 alloy and were dispersed uniformly using a power-driven stirrer. The melt with the dispersed particulate reinforcements was then poured into a thoroughly dried sand mold, and the melt was allowed to solidify. The quality of the castings was ascertained through density evaluation followed by a microstructural examination. It was found that the composites with only the fly ash particles as a reinforcement were less dense in comparison to the composites cast with the quartz particulate reinforcement. However, the hybrid composite, with both particulate reinforcements were dense. The microstructure revealed a refined grain structure. The thermal diffusivity and thermal conductivity values were lower for the composites cast with only the fly ash reinforcement. On the other hand, the composites cast with only quartz as the particulate reinforcement exhibited higher thermal diffusivity and thermal conductivity. The specific heat capacity was found to be lower for the fly ash-reinforced composites and higher for the quartz-reinforced composites in comparison to the LM13 base matrix alloy. However, the highest value of thermal diffusivity and thermal conductivity were reported for the hybrid composites with a 10 wt.% inclusion of both fly ash and quartz particulate reinforcements.

Influence of ageing temperature on the tribological characteristics of LM25/Al2O3/SiC hybrid metal matrix composite for lightweight applications

The demand for hybrid composites has lately increased due to their extraordinary qualities, which include unique mechanical, tribological, and physical capabilities not found in other materials. These composites improve performance and utility by mixing different reinforcing components, making them highly sought after. However, there is a study gap on the effects of long-term ageing on the tribological characteristics of LM25 (Al–6.6Si–0.2Mg)/Al2O3/SiC metal matrix composites (MMCs). As a result, extensive studies on the influence of ageing temperature on the tribological properties of LM25/Al2O3/SiC MMCs via long-term ageing effects still need to be included. Therefore, this study investigated the metallurgical and hardness properties of stir-cast LM25 alloy reinforced with Al2O3 and SiC particulates with varying ageing temperatures. Furthermore, dry sliding wear behaviour is also examined. The investigation concluded that adding micron-sized Al2O3 and SiC particles to LM25 improves hardness and tribological properties. As the ageing temperature increased, the eutectic particles became coarser. Furthermore, the result illustrates that the coefficient of friction (COF) values also enhanced with wear rates. Higher loads increased the wear rate and COF, whereas higher sliding speeds decreased the COF and wear rate.

INFLUENCE OF NICKEL ON THE MICROSTRUCTURAL EVOLUTION AND MECHANICAL PROPERTIES OF LM6-ALLOY-BASED FUNCTIONALLY GRADED COMPOSITE TUBES

Despite the growing demand for new materials, we used the horizontal centrifugal casting technique to synthesize functionally graded composite (FGC) tubes using an LM6 alloy containing (3, 6 and 9) w/% nickel. All the fabricated tubes were evaluated for variations in microstructure, hardness and tensile properties along the radial cross-section in three distinct zones (inner, transition and outer). X-Ray diffraction (XRD) results indicated the formation of in-situ Al3Ni in all FGC tubes, and these in-situ tri-aluminides increased further with the addition of Ni. A comprehensive microstructural analysis across the tubes utilising scanning electron microscopy (SEM) images showed that gathering in-situ Al3Ni particles keeps growing nearer the outer zone, and primary Si cuboids increase in the inner zone. This accumulation of particles improved the mechanical properties at all three zones of the FGC tubes compared to the LM6 tube having no nickel. The results of the hardness investigation showed that precipitated Al3Ni in FGCs has a beneficial impact on the enhancement of hardness. Furthermore, the observed UTS improvement in the FGC tubes was clearly associated with the precipitation and strengthening action of Al3Ni intermetallic phases, while a significant reduction in elongation has been noted. Due to the influence of centrifugal force and density variation, the tube containing 9 w/% of Ni demonstrated good gradation among composite alloy-fabricated FGC tubes, with in-situ Al3Ni particles settling largely in the outer zone and primary Si particles settling primarily in the inner zone across the radial thickness.

Enhancing mechanical and functional properties of LM25 alloy through squeeze cast hybrid nanocomposite incorporating breadfruit seed husk ash and graphite nanoparticles

ABSTRACT In this research, effective utilization of agro waste breadfruit seed husk ash particle (SHA) as reinforcement purpose in LM25 alloy matrix enhanced with the inclusions of 3, 6, and 9wt% of graphite (Gr) nanoparticle (50nm) via squeeze cast liquid processing executed with 200MPa applied compressive pressure. This developed cast examined LM25 alloy and its composites for density, percentage of porosity, microstructure, ultimate tensile strength, abrasion, and corrosion behaviour. From the experimental result, the LM25/10wt% SHA/9wt% Gr hybrid nanocomposite has low density (2.554g/cc), an excellent ultimate tensile strength of (181±1.8 MPa), superior abrasion resistance (0.332mg/m) under 40N load at 0.75m/sec, and good corrosion resistance (0.00382mm/year) compared to cast LM25 alloy. The inclusions of SHA and Gr proved their presence in LM25 alloy has good mechanical strength and maximum abrasion and corrosion resistance to overcome the drawbacks of conventional stir-casted LM25 alloy, which is poor wear resistance.

Friction stir extrusion and mechanical alloying of LM13 casting ingot to produce LM28 tubes

Friction Stir Extrusion (FSE) is applied on the as-cast LM13 aluminum alloy to produce tubes accompanied with the microstructural modification. Then, the process was employed to transform LM13 to LM28 alloy by mechanical alloying by adding Si particles during the process. In addition, a numerical model on the Deform 3D software is developed to simulate the process and investigate the temperature and strain distributions at different zones as well as the material flow over the process. The experimental and numerical results show that the peak temperature and strain of 460 °C and 200 are attained in the zone 6–10 mm after the conical part finish, where the material completely enters the tube channel. The temperature and strain distributions were varying through the tube wall, and the result is that the average Si precipitates’ size in the wall inside reduced to almost 0.8 μm while is 2 μm at the center of the tube wall. Furthermore, the material flow from the primary cylindrical ingot towards the tube wall was not uniform in the sample cross-section due to tool design, and the velocity of material movement at various zones was different. Mechanical alloying of LM13 alloy, by the addition of Si particles in ∼6 %, transformed the alloy to LM28 by increasing the silicon content from 12.2 to 19.2 %. The ultimate compression strength of the LM13 base metal increased from 84.7 to 138.7 MPa and 158.2 MPa, respectively, for LM13 and LM28 by breakage of needle-like Si precipitates and fine dispersion of them in the aluminum substrate.

Optimization of squeeze casting process parameters on mechanical properties of SiCp reinforced LM25 composites through Taguchi technique

Abstract The aim of the present work is to examine the influence of processing parameters on fabricated composites of LM25 alloy with SiC particle reinforcement through a squeeze casting technique. The following process parameters, like stirring speed from 550 to 750 rpm, SiCP (4 wt% to 8 wt %), and melting temperatures (from 600 to 700 °C) were employed. Then, the processed composites were subjected to microscopy analysis and mechanical tests to ascertain their metallurgical and mechanical properties. SEM micrographs of an LM 25 composite sample show better bonding of SiC particles with matrix, which is due to homogeneous dispersion of SiC particles in the stir casting process. The maximum tensile strength (211 MPa) and hardness (91 Hv) were achieved on the composite samples with processing parameters of 750 rpm stirring speed, 8% SiC proportions, and 650 °C melting temperature, respectively. From the design of the experiment by the Taguchi method, it is observed that the stirring speed plays a significant role in achieving a better distribution of SiC particles in the composite samples than other parameters like SiC weight ratios and the melting temperature of the alloy.

Experimental investigation of powder mixed electrical discharge machining of LM-25/SiC composites: A response surface methodology coupled with desirability approach

ABSTRACT In the last few years, many experiments have been done on lightweight Al and SiCp MMCs for aerospace and automotive applications. The results have been consistent in the development of structural and super alloys. Present work explores the performance characteristics of powder mix EDM by machining Al, LM-25 alloy with various weight fractions of reinforcement (0%, 5%, and 10% SiC) and variable electrode material. The impact of heat treatment on the microstructure of Al LM-25/10%SiC MMC has also been examined. Experimental investigation has been conducted to examine the machine response by adjusting the process parameters by employing the statistical design of RSM. The machining characteristics have been estimated to assess the machine response, namely metal removal rate (MRR) and tool wear rate (TWR), which are closely related to process variables, discharge current (I p), pulse on time (Ton), servo voltage (V), different tool materials, varying work materials, and differing concentrations of abrasive particles. The ANOVA results show that tool material is the most crucial parameter for MRR, accounting for 11.90% of the total, followed by other process variables, and the pulse on time for TWR, accounting for 5.94% of the total. Scanning Electron Microscope (SEM) was used to examine the macrostructure of machined MMCs. A chemical microanalysis technique such as Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) was used to determine the phase composition of the materials and material dispersion. Additionally, the desirability technique was used to identify the optimum machining conditions.

Evaluation of Mechanical Properties and Corrosion Behavior of Stir Cast Hybrid Composites Based on LM13 Aluminum Alloy Reinforced with Zirconium Diboride (ZrB2) and Titanium Carbide (TiC) Particles

Abstract: In the LM13 alloy matrix, ceramic titanium carbide (TiC) and zirconium diboride (ZrB2) particles were used to create and characterise hybrid composites. TiC's weight percentage stayed constant at 5% whereas ZrB2's weight percentage was changed from 0% to 10%. The microstructure of the composites was analysed using an optical microscope after they were made using the liquid metallurgy stir casting technique. The mechanical properties of the composites, including their tensile strength, ductility, and hardness, were evaluated and compared to those of the LM13 alloy without reinforcement

Effect of strontium modifier on the microstructure, mechanical properties and fractography analysis of as-cast Al-Si7Mg0.3 alloy

ABSTRACT Al-Si7Mg0.3 (LM25/A356) alloy is mainly used in cast form and the microstructure of LM25 alloy mainly depends on the rate of solidification and composition of modifiers. This study explores the influence of the strontium modifier on the microstructural changes, mechanical properties and fractography analysis of the Al-Si7Mg0.3 (LM25) alloy. Optical microscopy (OM), scanning electron microscopy (SEM) and X-Ray Diffraction (XRD) analysis were performed on the LM 25- x% Sr (x = 0.01, 0.02, 0.03, 0.04 and 0.05) specimens to study the grain refinement, modifier distribution and elemental peaks in the as-cast samples. Experimental results concluded that the agglomeration generated at the 0.05 % Sr modifier added with LM25 alloy and the elements corresponding to this agglomeration was confirmed as strontium oxide (SrO) by using JCPDS file numbers. The maximum ultimate tensile strength of 173 MPa, yield strength of 132MPa and hardness of 103 VHN were obtained at 0.04 % strontium added LM 25 alloy. The ductile fracture was confirmed based on the dimples generation on the fractured layer of 0.01 %, 0.02 % and 0.03 % Sr added LM 25 alloy and the fracture mechanism was changed to brittle mode with the addition of 0.04 % and 0.05 % Sr.

Tribological characteristics of LM13 alloy based ilmenite-boron carbide reinforced hybrid composites for brake drum applications

Aluminium matrix hybrid composites reinforced with a combination of naturally occurring ilmenite mineral particles (FeTiO3) and synthetically processed boron carbide ceramic particles (B4C) were processed using stir casting route. Reinforcement loading was varied between 0 and 15 wt. percentage (wt.%). For each loading, the two type of fillers were mixed in three wt.% ratio of 1:3, 1:1, and 3:1. Particle size range for both fillers was 106–125 μm. Operating temperature, applied load, and sliding distance were in the range of 25–300 °C, 9.8−49.0 N, and 0−3000 m respectively. Optical and scanning electron micrographs showed nearly uniform distribution of reinforced particles in the matrix. Grain size reduction and morphological changes in the constituent phases of matrix material were noted. Pin-on-disc wear set-up was used to evaluate the wear behaviour of composites (ASTM G99 standard). With increase in operating temperature, the wear rate increased. A sharp rise in wear rate was observed beyond 200 °C. 15HA-31 composite (loading: 15 wt.%; B4C to Ilmenite weight ratio: 3:1) showed maximum improvement in wear rate at all the operating temperatures exhibiting 52−71% reduction in maximum wear rate over the reference sample. Ilmenite particles reduced the coefficient of friction, promoted strong interfacial bonding, and caused early oxidation of sliding surface. On the other hand, B4C particles increased the stability of tribolayer, caused grain refinement, and resulted in morphological changes from acicular to globular for the constituent phases of matrix. Wear rate behaviour of 15HA-31 composite was comparable to the commercially used brake drum material.

Microstructure Evolution and Fracture Toughness Behaviour of Cryorolled LM6 Al Alloy

In the present work, the effect of cryo-rolling on the processed LM6 alloy samples has been studied. The solution treated (ST) sample of LM6 alloy has been processed through cryo-rolling with reduction of its thickness with values such as 30%, 40%, and 75%. One of the key material properties i.e., fracture toughness has been studied and equivalent energy fracture toughness ( ) is being evaluated according to the ASTM E 992 standard. The microstructure evolution after processing through cryorolling (CR) has been carried out with the help of optical microscopy and Scanning Electron Microscopy (SEM). Then, the calculated values of fracture toughness parameter i.e., equivalent energy fracture toughness ( is being correlated with the microstructure evolution after processing of LM6 alloy. It was found out that there is an improvement in equivalent energy fracture toughness ( ) as the reduction values increases. The 75% CR sample showed great increment of 67% as compared to ST alloy sample. The microstructure evolution also signifies the mix-mode fracture visualized through Scanning Electron Microscopy (SEM) and as the reduction values increase, the ductile fracture zone dominance increases on brittle fracture zone indicating there is improvement in fracture toughness of the ultra-fined grain LM6 alloy due to the grain refinement, dislocation strengthening and grain boundary strengthening.

Fabrication and Characterization of SiC-reinforced Aluminium Matrix Composite for Brake Pad Applications

The wear debris from conventional brake pads is a growing source of environmental contamination that often leads to life-threatening diseases for human beings. Though the emerging organic brake pads show potential to serve as an eco-friendly alternative, their mechanical and tribological properties are not adequate to withstand the demands of high-wear resistance of a functioning braking system under regular use. Metal matrix composites have served as an optimal solution with minimal environmental pollution and appreciable physical properties. Owing to the popularity of aluminium metal matrix composites, the present study is based on the fabrication and characterization of SiC-reinforced LM6 alloy through stir casting methodologies for evaluating its worthiness in application as a brake pad material. Microstructural, compositional, and phase characterizations were executed through optical micrography, X-ray diffraction, and energy-dispersive X-ray spectroscopy analysis. Although mechanical properties were evaluated through surface hardness investigation, parallel thermal properties were estimated through thermal conductivity evaluation. Finally, the execution of tribological analysis and precise microstructural observations of wear track at ambient and elevated temperatures helped in establishing the datum that the fabricated metal matrix composite (MMC) is a reliable brake pad material alternative.

Response surface modeling and optimization of LM25 alloy-based hybrid composites reinforced with red mud and sillimanite particles

The present study investigates the tribological behavior of aluminum and silicon (Si) alloy (LM25) based hybrid metal matrix composite (MMC). LM25 alloy is reinforced with three different percentages (5, 10, and 15 wt. %) in a 1:1 ratio of sillimanite and red mud particles utilizing the stir casting method. An analysis of the microstructure shows morphology of reinforcement particles throughout the alloy matrix. Pin-on-disk tests have been performed as per the Box-Behnken Design (BBD) technique to evaluate wear and friction characteristics. Further effect of reinforcement, sliding velocity, and applied load on wear and friction characteristics were analyzed and optimize as 13.48 wt. % reinforcement, 10 N load and 1.5 m/s sliding speed to get optimum properties. SEM analysis showed that the composite surface was more susceptible to wear under high loads since it had a higher degree of deformation.

Impact of aging temperature on the metallurgical and dry sliding wear behaviour of LM25 / Al2O3 metal matrix composite for potential automotive application

The current study exhibits the influence of aging temperatures on the metallurgical, hardness, and dry-sliding wear behaviour of LM25 (Al-6.6Si-0.2Mg) alloy reinforced with Al2O3 particles. The LM25 alloy reinforced with 10 wt% of alumina particles was fabricated using the liquid metallurgy route followed by solutionizing and aging. The baseline LM25 alloy and its composite were solutionized at 538 °C for 8 h and were aged at 155, 165, and 175 °C for 12 h. Optical, FESEM, EDS, and X-ray diffraction analysis were done on the fabricated alloy and its composite in all conditions. The microstructure revealed the formation of the Mg2Si phase in the baseline alloy and the MgAl2O4 spinel generated at the composite interface of the aluminium matrix. The heat-treated alloy and composites were tested for their hardness on the Vickers microhardness tester. It was concluded that the aging temperature of 155 °C displayed significant enhancement in hardness values for tested samples. The heat-treated alloy and composite samples displayed an increment of 96% and 55% in hardness values relative to LM25. The wear rate and friction coefficient for the fabricated samples were analyzed using the pin-on-disc tribometer under dry sliding conditions. The hardness value increased from the as-cast state to samples aged at 155 °C and then decreased at 165 and 175 °C. Based on the wear study, a 14% and 25% decrease in the wear rate values for heat-treated alloy and composites were noted when sliding velocity was increased from 1 m/s to 3 m/s. However, the coefficient of friction (COF) decreased by 23% and 13% for the specimens in the same conditions. Furthermore, a similar trend was displayed by age-hardened LM25 alloy and the composite when subjected to varying load (5, 10, 15 N) condition. Lastly, the worn-out surface mechanisms were examined using FESEM analysis. Amongst the investigated samples, LM25/10 wt% Al2O3 composite aged at 155 °C revealed the least wear rate when subjected to an external load of 5 N and sliding velocity of 2 m/s. Therefore, it can be suggested to manufacture components in the automotive industry.