Vyasaraj Manakari

Enhancing the hardness/compression/damping response of magnesium by reinforcing with biocompatible silica nanoparticulates

Abstract Low volume fraction silica nanoparticulate-containing magnesium composites targeting structural and biomedical applications were synthesized using the blend–press–sinter powder metallurgy technique followed by hot extrusion, and subsequently characterized for their microstructural, mechanical and damping properties. The results of microstructural characterization revealed a maximum ∼32% reduction in grain size with 2 vol.% addition of SiO2 nanoparticulates. The compressive properties of pure magnesium increased with the addition of SiO2 nanoparticulates with Mg-2 vol.% SiO2 nanocomposite exhibiting the maximum 0.2% compressive yield strength and compressive fracture strain. The addition of SiO2 nanoparticulates enhanced the damping characteristics of pure magnesium with Mg-2 vol.% SiO2 nanocomposite exhibiting the maximum damping capacity and damping loss rate with a minimum change in elastic modulus which is favorable when targeting magnesium for biomedical applications. An attempt has also been made in this study to compare the biomechanical properties of synthesized Mg–SiO2 nanocomposites with those of natural bone.

Using B4C Nanoparticles to Enhance Thermal and Mechanical Response of Aluminum

In this work, Al-B4C nanocomposites were produced by microwave sintering and followed by hot extrusion processes. The influence of ceramic reinforcement (B4C) nanoparticles on the physical, microstructural, mechanical, and thermal characteristics of the extruded Al-B4C nanocomposites was investigated. It was observed that the density decreased and porosity increased with an increase in B4C content in aluminum matrix. The porosity of the composites increased whereas density decreased with increasing B4C content. Electron microscopy analysis reveals the uniform distribution of B4C nanoparticles in the Al matrix. Mechanical characterization results revealed that hardness, elastic modulus, compression, and tensile strengths increased whereas ductility decreases with increasing B4C content. Al-1.0 vol. % B4C nanocomposite exhibited best hardness (135.56 Hv), Young’s modulus (88.63 GPa), and compression/tensile strength (524.67/194.41 MPa) among the materials investigated. Further, coefficient of thermal expansion (CTE) of composites gradually decreased with an increase in B4C content.

Improved properties of Al–Si3N4 nanocomposites fabricated through a microwave sintering and hot extrusion process

In this study, nano-sized Si3N4 (0, 0.5, 1.0 and 1.5 vol%)/Al composites were fabricated using a powder metallurgy method involving microwave sintering technique followed by hot extrusion. The influence of Si3N4 content on the structural, mechanical and thermal behaviour of Al–Si3N4 nanocomposites was systematically investigated. Electron microscopy examination reveals the uniform distribution of hard Si3N4 nanoparticles in the soft Al matrix. The compressive and tensile strengths of Al composites increased with the increase of Si3N4 content while the ductility decreased. The thermal expansion coefficient of the Al composite decreased with the progressive addition of hard Si3N4 nanoparticles. Overall, hot extruded Al–1.5 vol% Si3N4 nanocomposites exhibited the best combination of tensile, compressive, hardness, Youngs modulus and thermal properties of 191 ± 4 MPa, 412 ± 3 MPa, 16.3 ± 0.8 GPa, 94 ± 2 GPa and 19.3 μ K−1, respectively. Tensile tests performed at 200 °C revealed that the tensile strength reduced by ∼35% when compared to the strength at room temperature. The strength, however, was still higher compared to that of the pure Al at 200 °C. The major enhancement in the strength of the nanocomposites is primarily attributed to the presence of uniformly distributed nano-sized Si3N4 nanoparticles in the Al matrix.

Enhancing the Ignition, Hardness and Compressive Response of Magnesium by Reinforcing with Hollow Glass Microballoons

Magnesium (Mg)/glass microballoons (GMB) metal matrix syntactic foams (1.47–1.67 g/cc) were synthesized using a disintegrated melt deposition (DMD) processing route. Such syntactic foams are of great interest to the scientific community as potential candidate materials for the ever-changing demands in automotive, aerospace, and marine sectors. The synthesized composites were evaluated for their microstructural, thermal, and compressive properties. Results showed that microhardness and the dimensional stability of pure Mg increased with increasing GMB content. The ignition response of these foams was enhanced by ~22 °C with a 25 wt % GMB addition to the Mg matrix. The authors of this work propose a new parameter, ignition factor, to quantify the superior ignition performance that the developed Mg foams exhibit. The room temperature compressive strengths of pure Mg increased with the addition of GMB particles, with Mg-25 wt % GMB exhibiting the maximum compressive yield strength (CYS) of 161 MPa and an ultimate compressive strength (UCS) of 232 MPa for a GMB addition of 5 wt % in Mg. A maximum failure strain of 37.7% was realized in Mg-25 wt % GMB foam. The addition of GMB particles significantly enhanced the energy absorption by ~200% prior to compressive failure for highest filler loading, as compared to pure Mg. Finally, microstructural changes in Mg owing to the presence of hollow GMB particles were elaborately discussed.

Using lanthanum to enhance the overall ignition, hardness, tensile and compressive strengths of Mg-0.5Zr alloy

Abstract Near dense Mg 0.5 wt.% Zr (0, 1, 2.5 and 4) wt.% La alloys were successfully synthesized by disintegrated melt deposition technique followed by hot extrusion and were characterized for their microstructural, ignition, hardness, tensile and compression properties. Combined effects of Zr and La assisted in significant grain refinement of Mg and Mg 0.5 wt.% Zr 4 wt.% La exhibited an average grain size as low as ∼2.75 µm. High ignition temperature of ∼645 °C was realized with Mg 0.5 wt.% Zr (1, 2.5 and 4) wt.% La alloys. Microhardness value as high as ∼103 Hv was observed with Mg 0.5 wt.% Zr 4 wt.% La alloy. Under room temperature tensile and compression loading, significant improvements in the strength properties of pure Mg with the addition of 0.5 wt.% Zr (0, 1, 2.5 and 4) wt.% La was observed. Mg 0.5 wt.% Zr 4 wt.% La exhibited the maximum 0.2% tensile and compression yield strengths of ∼283 MPa and ∼264 MPa, respectively. The tensile and compression fracture strain values of synthesized pure Mg were found to be unaffected with the addition of 0.5 wt.% Zr. But the tensile fracture strain reduced with the addition of La while the compressive fracture strain was unaffected. Minimal tensile-compression asymmetry (∼1) was exhibited by Mg 0.5 wt.% Zr (1 and 2.5) wt.% La alloys.

Effects of Hollow Fly-Ash Particles on the Properties of Magnesium Matrix Syntactic Foams: A Review

In the past decade, magnesium has been seen as one of the most potential metals for weight-critical engineering applications. As magnesium is the lightest structural metal, it has higher weight-saving capabilities when compared to aluminum. Significant research efforts have been carried out on magnesium matrix alloys and composites to tailor and enhance mechanical properties based on end applications. This paper provides a review on fly-ash-reinforced magnesium matrix syntactic foams. Fly-ash cenospheres are made up of mainly alumina and silica and also contains large number of trace elements, which makes it intriguing to analyze the microstructure and interfacial responses of the end composites. In comparison with aluminum matrix syntactic foams, the research on magnesium matrix syntactic foams is still at an incipient stage. This paper provides an insight on processing techniques, microstructural and mechanical evaluations of pure Mg, AZ, and ZC alloy series, and their syntactic foams. This paper also reviews the weight-saving ability of magnesium matrix syntactic foams and their potential scope and applications.

Wear Response of Walnut-Shell-Reinforced Epoxy Composites

Present work utilizes agricultural by-product, walnut shell, as reinforcing filler in epoxy matrix for investigating dry sliding wear behavior using a pin-on disc wear-testing machine. Effects of sliding velocity (0.5–1.5 m/s), normal load (10–50 N), sliding distance (1000–3000 m) and filler content (10–30 wt. %) on wear rate (Wt), specific wear rate (Ws) and coefficient of friction (μ) are investigated. The experiments were planned as per design of the experiments scheme and the wear characteristics were analyzed through response surface modeling (RSM) method. The lowest Wt of 1.1 mm3/km was noted for 1.5 m/s sliding velocity with 30-wt. % filler content. Sliding distance did not have a significant influence on Ws above a critical load of 40 N. The minimum μ was observed at 1-m/s sliding velocity, 40-N load, 1000-m sliding distance, and 30-wt. % filler. Lower values of Wt and μ at higher walnut-shell loadings support feasibility of using such composites in wear-prone applications. The wear mechanism was determined in the composites using extensive scanning electron microscopic observations.

An Insight Into Use of Hollow Fly Ash Particles on the Properties of Magnesium

In the recent years, magnesium based materials has received wide acceptability and attention owing to their attractive properties like high specific strength, high specific stiffness, low density, excellent machinability, castability, and good damping properties. Therefore, they have become a promising choice for applications in the automotive, transport, aerospace and electronic packaging industries [1, 2]. Magnesium is also a biocompatible material and is an important constituent of the bone. The volume of scientific publications on the research of magnesium as a biomaterial has increased exponentially in the past 8–10 years. Further, when compared to other light metals, the Young’s modulus of magnesium based materials (40–45 GPa) is comparable to that of natural bone (3–20 GPa). This property of magnesium materials assists in mitigation of stress shielding effects with possibility to eliminate secondary surgery for the implant removal especially for clinical applications [3]. However, costs incurred during the synthesis of these materials are a major limitation. Fly ash cenospheres are alumino-silicate particles which are mainly a by-product of coal combustion in thermal power plants with an extremely low density of about 0.4–0.8g/cc [4]. The incorporation of fly ash particles into magnesium is an encouraging option for light-weight applications as the replacement of magnesium matrix by fly ash particles can further decrease the density of the composite and also the overall cost of raw materials [5]. The addition of hollow particles like cenospheres into polymeric or metallic matrices results in a special type of closed cell foams known as syntactic foams. For the past decade, a lot of research has been carried out mainly on aluminium syntactic foams and researchers have reported enhanced compressive strength and modulus, isotropic behaviour, high energy absorption and attractive strength to weight ratio [6, 7]. Moreover, the addition of fly ash cenosphere particles in composites is an effective way to reduce the carbon emissions and thereby finding applications in automotive, aerospace and military applications. The effect of fly ash cenosphere particles addition in magnesium based alloys and composites have become an encouraging area for researchers for the past 10 years. As magnesium is expanding into more critical structural applications, there is a need to tailor the properties of magnesium syntactic foams for potential use in lightweight energy absorbing components. This paper focuses on magnesium matrix syntactic foams which contain porosity in the form of hollow fillers and a review of our recent findings in the study of magnesium syntactic foams synthesized by disintegrated melt deposition technique.