Pure iron has been demonstrated as a potential candidate for biodegradable metal stents due to its appropriate biocompatibility, suitable mechanical properties and uniform biodegradation behavior. The competing parameters that control the safety and the performance of BMS include proper strength-ductility combination, biocompatibility along with matching rate of corrosion with healing rate of arteries. Being a micrometre-scale biomedical device, the mentioned variables have been found to be governed by the average grain size of the bulk material. Thermo-mechanical processing techniques of the cold rolling and annealing were used to grain-refine the pure iron. Pure Fe samples were unidirectionally cold rolled and then isochronally annealed at different temperatures with the intention of inducing different ranges of grain size. The effect of thermo-mechanical treatment on mechanical properties and corrosion rates of the samples were investigated, correspondingly. Mechanical properties of pure Fe samples improved significantly with decrease in grain size while the corrosion rate decreased marginally with decrease in the average grain sizes. These findings could lead to the optimization of the properties to attain an adequate biodegradation-strength-ductility balance.

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Zircon, ZrSiO4, is a thermally stable mineral requiring expensive and energy-intensive process to reduce. Owing to its abundance, high hardness, excellent abrasion/wear resistance, and low coefficient of thermal expansion, a low-cost alternative use of the mineral for medium-strength tribology was investigated. The present study has developed a conventional low-cost, double-compaction powder metallurgy route in the synthesis of AI-13.5Si-2.5Mg alloy reinforced with zircon. The mechanical and physical properties were determined following the development of optimum conditions of cold pressing and reaction sintering. Reinforcing the hypereutectic AI-Si alloy with 15 vol% zircon particles (size < 200 lam) and cold pressing at 350 MPa to near-net shape, followed by liquid-phase reaction sintering at 615 ~ in vacuum for 20 rain, improved the ultimate tensile strength, 0.2 % yield strength, and hardness of the alloy by 4, 12.8, and 88 %, respectively. At values of more than 9 vol % zircon, percent elongation and the dimensional changes of the sintered composites remained virtually unchanged. At a critical volume fraction of zircon, between 0.03 and 0.05, a sharp rise in hardness was observed. Microstructural and mechanical property analysis showed that the improvement in the mechanical properties is attributable largely to the load-bearing ability and intrinsic hardness of zircon, rather than to particulate dispersion effects. A good distribution of the dispersed zircon particulates in the matrix alloy was achieved.

In the present study, the structural modification of sand cast Al-12wt%Si alloy with sulfur/sodium and its effect on mechanical properties were investigated. Different addition levels of sulfur and sodium were used to modify and produce castings of the same shape and size from the alloy. The results indicated that the addition of sodium or sulfur to eutectic Al-Si alloy can modify the Al-Si eutectic morphology from needle-like eutectic silicon structure to fine-scale eutectic silicon structure with significant improvement in mechanical properties of the alloy. The optimum levels of modification by sodium flux (60% NaF and 40% NaCl) and sulfur were found to be 0.6%-1.0% and 0.02%-0.05% of the weight of the alloy respectively. The alloy modified with 0.6% Na flux had the best mechanical properties closely followed by the one modified with 0.02% sulfur. Over modification of the alloy with sodium produced over modification band which consisted of aluminum dendrites and coarse silicon particles in the microstructure of the alloy. Increase in concentration of sulfur decreased the degree of fineness of the eutectic silicon structure with significant decrease in mechanical properties of the alloy and this is suggested to be as a result of the presence of a brittle sulfur compound at the grain interfaces of the alloy.

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ABSTRACT:The corrosion of mild steel (uncoated), galvanized steel and stainless steel (304L) have been studied using the weight loss method over a period of 98 days with measurements made at 14 days' interval in ground melon (locally called egusi), cassava pulp, mashed palm fruit, tomato pulp, and black-eyed bean pulp respectively. The results obtained show that the average corrosion rates of 304 stainless steel, galvanized steel and mild steel are in ground melon

Ceramic tiles were processed in this present work using clay mineral and steel slag. Steel slag in the range of 0 -100 wt% was added to kaolinite clay. The blended samples were hydraulic pressed into rectangular moulds, oven dried and sintered to 1200˚C. Linear shrinkage, apparent porosity, water absorption, bulk density, and modulus of rupture of sintered specimens were examined. Phases present in the sintered products were identified using X-ray Diffractometer (XRD), while the microstructural examination was conducted using Scanning Electron Microscopy (SEM). The elements present in the sintered products were identified using Energy Dispersive X-ray (EDX). Phases like quartz, wollastonite, anorthite and enstatite were identified in the sintered products. The SEM revealed crystals embedded in the glassy matrix. EDX studies detected Aluminum (Al), Silicon (Si), Magnesium (Mg) and Calcium (Ca) as the major metal ions. Results obtained showed that samples containing 20 -60 wt% steel slag have very good usable ceramic tile properties.

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