Investigations were carried out to study critically the effects of heat treatment on the properties of rolled medium carbon steel. Representative samples of as-rolled medium carbon steel were subjected to heat treatment processes which are; Quenching, Lamellae Formation and Tempering in the following order (Q + Q + L + T), (Q + L + T) and (L + T). The steel was heated to the austenizing temperature of 830 ºC and water quenched. The quenched steel was subjected to lamellae formation by reheating it to the ferrite-austenite dual-phase region at a temperature of 745 ºC below the effective A C3 point and then rapidly quenched in water. The lamellae formed was tempered at 480 ºC to provide an alloy containing strong, tough and lath martensite in a soft and ductile ferrite matrix. Mechanical tests were carried out on the samples and the results shows that the steel developed has excellent combination of tensile strength, hardness and impact strength which is very good for structural applications. The corrosion behaviour of the samples; heat treated rolled medium carbon steel and as-rolled medium carbon steel in sodium chloride medium were also investigated from where it was also confirmed that improved corrosion resistance is achievable by the treatment.

This work was carried out to investigate the effect of welded joints on the mechanical properties of wrought (6063) aluminium alloy. The study revealed the influence of current and voltage on the welded joint as well as the mechanical properties of the alloy. The alloy samples were welded together by metal inert gas welding process at varying values of current and voltage after which mechanical tests were performed on the welded samples. The microstructural examination of the various fusion zones obtained was carried out. Appreciable variations in the properties of the welded samples were observed due to changes in the microstructural features of the alloys. It was concluded that variation of current and voltage remarkably affect the mechanical properties of the wrought 6063 Aluminium alloy. As the voltage increases from 25 to 30 V, the ultimate tensile strengths and hardness values increases while the impact strengths decreases but the current did not show such trend.

The variation of welding parameters such as weld geometry and post-weld heat treatment on the corrosion behaviour of austenitic stainless steel in a saline environment of 1.0 M NaCl was investigated in this work. Rods of austenitic stainless steel of known chemical composition were prepared and welded using electric arc welding technique varying the aforementioned parameters. Thereafter, samples for the corrosion behaviour investigation were then cut out of the welded rods. The analysis of the experimental data revealed that the best weld geometry was chamfered and a post-weld heat treatment carried out at temperatures in excess of 700 °C followed by air cooling improves the quality of a weld.