Papers by Author: Manoj Gupta

Abstract: The current medical technology necessitates the usage of biodegradable metals like Magnesium (Mg) as the future implant material due to the numerous benefits it can provide. Therefore, new Magnesium-based rare earth alloys targeting biomedical applications were synthesized using Disintegrated Melt Deposition (DMD) technique followed by hot-extrusion. In this investigation, Zinc (Zn) and Erbium (Er) were chosen as alloying elements to provide suitable strengthening effect and Mg-2Zn, Mg-2Zn-2Er alloys were synthesized. With the addition of alloying elements, the grain size was reduced and several MgZn intermetallics were formed. Corrosion studies of as-extruded materials were done in 0.5 wt.% NaCl solution to elucidate the microstructure-corrosion relationship. Improved corrosion resistance is seen in the alloys in comparison to pure Magnesium. Addition of Erbium is seen to improve the protectiveness of the surface film formed during immersion. Both these elements have proven to increase the corrosion potential of Mg in NaCl solution.

Abstract: Ethical research that ensures the enhancement of quality of human life for present and future generations is the need of the day. This inherits the typical requirement to impose zero or minimal stress on the environment. Currently, planet earth is witnessing global warming and largely unpredictable weather changes, primarily due to greenhouse gas emissions. Transportation sector is one of the major engineering sectors contributing to greenhouse gas emissions. One way to mitigate/minimize these emissions is to use lightweight materials in the construction of vehicles for use in land, water, aerospace and space applications. Towards this, magnesium based materials are viable options which are suitable to replace aluminum based materials allowing ~ 35% weight saving on a component basis. As magnesium is abundant in nature and is a nutritional element, its availability and recyclability is not an issue. Accordingly, this paper will focus on the development of magnesium based nanocomposites capable of replacing conventional materials in multiple engineering and biomedical applications.

Abstract: A ternary micro Mg-0.5Zr-0.4Ce alloy is developed using disintegrated melt deposition method (DMD) followed by hot extrusion. The developed alloy exhibited superior mechanical properties i.e. microhardness, strength and ductility under tensile and compressive loading. In particular, the alloy exhibits excellent ductility (>25%) under both tensile and compressive loading. The mechanisms leading to strengthening and ductilization were examined through microstructural studies involving optical microscope, SEM and XRD texture analysis. Microstructure-property correlation studies are performed to understand these mechanisms.

Abstract: In this research study, two light weight multi-component high entropy alloys (HEAs) consisting of six constituent elements were synthesized. The high entropy alloy having a chemical composition of Mg₃₅Al₃₃Li₁₅Zn₇Ca₅Y₅ (atomic pct.) had a density of 2.25 g/cm³, while the high entropy alloy having a composition of Mg₃₅Al₃₃Li₁₅Zn₇Ca₅Cu₅ (atomic pct.) had a density of 2.27 g/cm³. The strategy of non-equiatomic composition, high entropy of mixing coupled with low density was applied in designing the alloy systems. Disintegrated melt deposition (DMD) technique was used to synthesize the materials and characterization studies were performed on as-cast materials. The present study emphasizes on examining and understanding the microstructural development in the two light weight high entropy alloys. The formation and presence of phases and microstructural evolution were studied by interchanging yttrium and copper. Microstructural observations revealed presence of multiple phases in the developed alloys and the simplification of the microstructure when copper is used instead of yttrium. Microhardness results revealed a significant increase in hardness of of both the HEAs (3.8 – 4.2 times) when compared to AZ31 commercial magnesium alloy.Keywords: High Entropy Alloy, Magnesium, Aluminum, Casting, Microstructure

Abstract: This work aims to investigate the effect of SiC addition on structural, microstructural and mechanical properties of developed Al-Sic nanocomposites. Al metal matrix composites reinforced by nanosized SiC particles were fabricated using high energy ball milling and microwave sintering process followed by hot extrusion. The XRD analysis indicated that the dominant components were Al and SiC. SEM/EDX micrographs showed homogenous distribution of SiC nanoparticles in Al matrix. Mechanical characterizations revealed that the addition of nanosize SiC particulates to a simultaneous increase in microhardnes, yield strength, ultimate compressive/tensile strength and reduction in ductility of the matrix. This improvement in mechanical properties can be attributed to the homogeneous distribution of reinforcement (SiC particles) and dispersion strengthening mechanism.

Abstract: Magnesium is the lightest weight metallic material that can be used in multiple engineering applications and biomedical sector as a structural material. It is abundantly available in earth’s crust and sea water and non-toxic in nature. Inherent to magnesium is its superior specific mechanical properties, high damping, electromagnetic shielding capability and ability to reduce carbon signature of the transportation sector.Magnesium is one of the widely available metal in earth crust and sea water. It is non-toxic and hence does not pose a health risk during recycling or waste dumping in natural water bodies. As a result, magnesium technology is sustainable and beneficial to planet earth and living organisms.Magnesium based materials are gradually being used in many applications and their performance and applications can further be stretched using the composite technology. Accordingly, the main scope of this paper is to highlight the enhancement of a number of properties of magnesium through the use of nanolength scale, amorphous and hollow reinforcements.

Abstract: Magnesium alloys with enhanced thermal stability are being developed for automobile engine applications. The available commercial Mg-alloys are usually alloyed with aluminum that are thermally stable only for T < 150^o C. Development of new Mg-alloys is underway and Mg-Sn alloys are a promising option. In Mg-Sn alloy, the Mg₂Sn phase has high thermal stability and is expected to enhance the high temperature properties. In this study, Mg-5Sn alloy is incorporated with Ag as a minor alloying element (0.175 wt. %). The creep behavior of the Mg-Sn-Ag alloy is investigated using the impression creep technique. The impression creep tests were carried out under punching stress in the range of 80-320 MPa and temperature of 373-573 K, for dwell times up to 5 hours. The results highlight that creep of the alloy was load and temperature dependent, i.e. increasing the load and temperature resulted in higher creep rates.

Abstract: Magnesium nanocomposites are promising materials for weight and strength critical engineering and biomedical applications. The addition of nano-particles to magnesium can improve hardness and strength without detrimental effect on the ductility which tends to occur when micron-size particles are added. Examples of magnesium nanocomposites reinforced with ceramic and metallic particles are provided and the microstructure, grain size, tensile, compressive and dynamic behavior are discussed.

Abstract: Crystalline Mg-Cu-Y alloy system was fabricated using the squeeze casting technique. Microstructure showed the multiphase structure composed of primary Mg rich phase distributed among the lamellae patterns, alternative layers of LPSO Mg phase and intermetallic phases. High microhardness and tensile strength of 104 HV and 223 MPa respectively were observed in the squeeze cast alloy. A good combination of compressive strength (706 MPa) and ductility (19%) was also achieved in the crystalline alloy which is unlikely to be attainable in amorphous Mg-Cu-Y system. The formation of LPSO phase in the current Mg-Cu-Y alloy mainly contributed to the high mechanical properties.

Abstract: Magnesium (Mg) alloys with 30 weight percentage (wt.%) of yttrium (Y) were gravity cast using copper mold and copper mold with air cooling. The results were benchmarked with Mg-30Y alloys produced using steel mold casting. It was found that the Mg-30Y alloys cast using the copper mold with air cooling exhibited the best mechanical properties, whereby the compression strength and the Vickers hardness value peak at 633 MPa and 137.6 HV respectively. Microstructural observations show that with increasing cooling rate, and hence increasing molten metal solidification rate, the dendrite structures are much finer due to enhanced nucleation rate. This is due to limited time for the dendrites to coarsen.