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Magnesium is regarded as a lighter metal because of its lowest density, which makes it advantageous for many sectors. It finds utility in several industrial applications such as aerospace, biomedical, and automotive. Magnesium is a potential material since current efforts are concentrated on lowering emissions, increasing efficiency without negatively affecting the environment, and enhancing the machine economy. In this work, the main goal is to achieve sustainable machining of magnesium under various cutting parameters and in different environments. The experiment shows more carbon emissions and forces recorded in dry conditions, than minimum quantity lubrication (MQL) and nano-MQL (NMQL) conditions. NMQL provides better results than dry MQL methods. Balance speed, feed, and DOC to minimize emissions, cutting forces, and power consumption.

AZ91D magnesium alloys with and without dispersed SiC particles were oxidized between 420 and 500°C in air. They oxidized to fine MgO oxide grains containing dissolved ions of Al. Their oxidation rates increased almost linearly, with an increase in the oxidation temperature and time. SiC particles did not oxidize during oxidation, and increased the oxidation resistance of the alloy through diminishing the exposed surface area. With the increase in the amount of the dispersed SiC particles from 5 to 10, and to 20 wt.%, the oxidation resistance progressively increased.

This investigation intends to come up with a cost-efficient and easily available bamboo leaf ash (BLA) which has high content of Silica, as an effective and complimenting reinforcement for the production of magnesium alloy-based metal matrix composites. By incorporating SiC and BLA reinforcement to AZ91D Mg alloy, the composites were made using the bottom pouring stir casting technique. The ratio between SiC and BLA in the composite, respectively, varied as 0:0, 6:0, 0:6, 4:2, 3:3, 2:4 wt.%. Fretting wear is one of the fundamental modes of wear for any mating parts which have vibration with low amplitude. In this study, an integrated Taguchi-TOPSIS is adapted to make the process variables more optimal for fretting wear of composites. Material composition, load, temperature, time, frequency and stroke length are selected as process parameters. The objective is to minimize the coefficient of friction, volume loss and surface roughness. Using the TOPSIS approach, the multi-criteria optimization approach was reduced to a single-criteria issue. The results revealed AZ91D/2 wt.% SiC/4 wt.% BLA, 10N, room temperature, 30-min, 30 Hz and 0.7 mm stroke as optimal parameters. Microscopic study demonstrates that fretting wear occurs in the partial slip zone for the composite tested at optimal condition. With temperature, the wear regime in composites shifts from partial slip to mixed fretting, whereas in alloys, the wear regime shifts from mixed fretting to gross slip. When the correct set of circumstances are available, hybrid composite can function well as a replacement for traditional materials in machineries vulnerable to fretting wear.

The effect of microconstituents on the corrosion and electrochemical behaviour of AZ91D alloy prepared by die-casting and ingot casting route has been investigated. The studies were carried out in 3.5% NaCl solution at pH 7.25 using constant immersion technique, potentiodynamic polarisation experiments and surface topographic analysis. Microstructural areas with aluminium concentration less than about 8% (primary α phase and surroundings) were found to be more prone to corrosion attack compared with either those with higher amount of aluminium (eutectic α phase and its surroundings) or β phase. Die-cast material with smaller grain size and fine β phase offered marginally higher corrosion resistance and better passivation compared with the ingot.

The influence of chloride ion concentration and pH on the corrosion and electrochemical behaviour of die-cast and ingot cast AZ91D alloy has been investigated. The experimental techniques used include constant immersion test, potentiodynamic polarisation and scanning electron microscopy. Die-cast and ingot showed a linear increase in corrosion rate and I_corr with increase in chloride ion concentration with a change in slope for ingot above 5% NaCl. Open circuit corrosion potential shifted to more negative (more active) values as chloride ion concentration increases. The corrosion rate and I_corr are very high in highly acidic conditions (1-2.0 pH) and tend to decrease as pH increases. A synergism has been observed between the effect of chloride ion concentration, pH and microstructure of the material. Observation of the corrosion morphologies revealed preferential attack on β (Mg₁₇Al₁₂) and adjacent α regions (α regions with higher Al content) in highly acidic and higher chloride ion concentrations.