Papers by Author: Siti Khadijah Alias

Abstract: Carburizing had been a renowned case hardening method for most metal which produced hard casing protecting the surface, resulting in improvement of the mechanical, wear and corrosion behaviour. Carburizing in solid medium offer low cost advantages, thus it is widely implemented. The objective of this study is to compare the carbon thickness layer formed after carburizing process at two different solid medium which is powder and paste form. ASTM A516 Grade 70 mild steel was use as the sample in this study. Carburizing process in both powder and paste medium are conducted at three different temperatures which are 850°C, 900°C and 950°C for 8 hours holding time and cooled in room temperature, for comparison purpose. The thickness layer observation and measurement was carried out using optical microscope and XRD analysis was also conducted to validate the carbon appearances. Rockwell hardness test was also performed before and after carburizing process. The findings from this study indicated that paste carburized samples induced deeper carbon diffusion compared to powder carburized samples. Higher carburizing temperature is also favorable in enhancing the thickness layer in both powder and paste carburized samples. It could be stated that comparable thickness layer could be achieve faster in paste carburized samples, compared to powder carburized samples, which can lead a more cost effective carburizing process.

Abstract: In this present study, the effect of tempering temperature of annealing-tempering combination processes, on microstructure as well as exploring the phase constituents of ductile iron through XRD analysis were performed. Ductile iron produced through conventional CO₂ sand casting method was performed annealing-tempering heat treatment processes by using change furnace method. Three different temperatures were investigated ranging from (i) 250 °C, (ii) 300 °C and (iii) 350 °C for 1.5 hours respectively. Standard metallographic observation and XRD analysis were done to characterize the microstructure and the constituents respectively. It is found that the graphite structure exist in both treated and untreated samples. Pearlitic structure was formed in the microstructure for heat treated samples. Ferritic-pearlitic matrix structure surrounding the graphite nodule has been shown in as-cast sample. Annealing-tempering process does not change the BCC ferrite peak in (200), (211), (220) and (310) planes shown in as-cast.

Abstract: The studies emphasis on the development of niobium alloyed ductile iron with higher strength comparing to unalloyed ductile iron. 0.5wt% to 2wt% niobium were added into mixture of ductile iron casting containing pig iron, carburizer and steel scrap, and nodulized through 1.6wt% Fe-Si-Mg addition in CO2 sand casting process. Samples were then machined according to TS EN 10001 standards for tensile test and ASTM E23 for Charpy impact test. In addition, Rockwell hardness test was also performed. Microstructure observations were made after 2% Nital chemical etched and the phase structures were validated through XRD analysis. It was found that addition of niobium in ductile iron provide significant enhancement in mechanical properties when compared to unalloyed ductile iron. Addition of higher amount of niobium had further increased the strength and impact toughness properties. The enhancement of the mechanical properties is expected to further expand the applications of ductile iron.

Abstract: Towards green material, fatigue life of unidirectional kenaf fibre reinforced epoxy composites was investigated made from the hand-layout technique. The composites were subjected to tension-tension fatigue loading at stress ratio of 0.5 and 5 Hz of frequency. Fibre content ratios were found to affect fatigue life on the low cycle fatigue regime strongly as illustrated with stress level versus cycles to failure. It is found that kenaf fibre reinforced epoxy composites with higher fibre content posses higher load carrying capacity and degradation rates.