Advanced Materials Research Vol. 576

Abstract: The aim of this paper is to investigate the corrosion behaviour of aluminium-copper-SiCp composite materials under palm oil biodiesel (POB). Corrosion behaviour test was performed using both weight loss and polarization methods for two different types of aluminium-copper-SiCp composite materials such as ACM 1(2% Cu, 20% SiC, and 78% Al) and ACM 2 (6% Cu, 20% SiC, and 72% Al). The materials were characterized using scanning electron microscope (SEM) for surface morphology. The results showed that corrosion rate of ACM 2 is higher than ACM 1 in presence of palm oil biodiesel due to the higher amount of copper in the composite which is more susceptible to corrosion. The surface morphology after corrosion test showed that chemical corrosion occurs on the surface due to the dominant of the fatty acid in the POB. Therefore, in this study it can be concluded that aluminium-copper-SiCp composite materials are susceptible to corrosion in biodiesel.

Abstract: Alloys for high temperature application always rely on their ability to form protective, dense Cr2O3 and Al2O3 scales. In case of Ni-Cr binary alloy, a minimum composition of Cr is required for the formation of continuous protective scale. However, addition of small amount of third element such as Al may results in decrease of required Cr composition to form protective scale. This study aims to clarify the effect of ternary element on the formation of protective scale quantitatively. Ni-Cr alloys composed with 2 mass% and 4 mass% of Al were exposed in oxidizing environment under Cr/Cr2O3, Fe/FeO and Ni/NiO oxygen partial pressure. The oxidation of all samples is following parabolic rate’s law. XRD and SEM results show that Al2O3 and Cr2O3 are formed internally. Parabolic rate’s constant of samples oxidized in Ni/NiO oxygen partial pressure is higher by few magnitude orders. Higher Al concentration decreases the parabolic rate’s constant. It is concluded that the formation of protective scale is enhanced by the addition of Al as ternary element in Ni-Cr alloys.

Abstract: Poly(lactic acid) (PLA) and kenaf bast fiber (KBF) were melt-blended using brabender into films in the PLA/KBF ratios of 100/0, 90/10, 70/30 and 50/50 for natural soil burial test. This formulation was used to study the biodegradability of PLA and PLA/KBF biocomposites. It was found that the decompositions of the biocomposite were faster than pure PLA. The SEM morphology of the tensile fracture surface of the 30% and 50% of PLA/KBF biocomposites presented larger pores and degradation areas than smaller KBF loading (10 wt%). This result shows that the addition of larger fibre loading to the PLA matrix increased the micropore surface area of the PLA/KBF biocomposite hence accelerated the decompositions time of the biocomposites.

Abstract: Anticorrosive oxide films were successfully prepared on AZ91D magnesium alloy by chemical conversion coating in La (NO3)3 electrolytes with and without NaVO3. The morphologies and chemical composition were characterized by optical microscope, scanning electron microscope (SEM) and energy dispersive analysis (EDX). The corrosion resistances of the oxide films were evaluated by salt immersion test. The result showed that the oxide film formed in electrolyte with NaVO3 is successful in providing superior corrosion resistance for AZ91D magnesium alloy.

Abstract: High Si steels (base steel and with addition of 0.1, 0.3, 0.5mass% Mo) were oxidized in a N2-3%O2-20%H2O atmosphere at 1150oC for 0.3-10.8ks. The oxidation kinetics showed that base steel has the highest weight gain. In contrast, 0.5Mo has the lowest weight gain. From SEM results, the scale thickness decreased as Mo content increased. Distribution of alloying elements showed that Mo is enriched in internal oxidation zone (IOZ) and played a role in slowing the outward diffusion of Fe, thus, producing a thinner Fe oxide scale and lower weight gain.

Abstract: This study focuses on the micromechanical properties of polylactic acid (PLA) reinforced with kenaf fiber (KF) and organo-montmorillonite (OMMT) hybrid biocomposite by using nanoindenter. Nanoindenter is an analytical device that can record small load and depth with high accuracy and precision which can be used to determine the modulus, hardness and other mechanical properties of nanomaterials. The result shows that the optimum properties of the hardness and elastic modulus were dominated by PLA-KF-OMMT hybrid composite.

Abstract: The main aim of this paper is to investigate the crystallinity and hardness properties of Al-Cu/SiCp matrix composite (AMC) materials. The materials were prepared using a noble stir casting technique by varying the percentage of Cu in the Al-Cu matrix. Qualitative X-ray analysis has been carried out to characterize the crystallinity of the Al-Cu/SiCp as-cast composite materials. Sample was cut and shaped into 25 mm×15 mm×4 mm in dimension then polished with diamond paste. X-ray diffraction diagrams were recorded using a transmission technique with a SHIMADZU Lab X (XRD-6000) X-ray generator operating at Cu Kα1 radiation. Hardness test was conducted using Vickers hardness tester (Mitutuyo, MVK-H2). The results indicated that a significant crystal growth was occurred in the composite materials due to increase of Cu from 2 to 4 % whereas a slight improvement of crystallinity was observed when the Cu percentage was increased from 4 to 6 % in the matrix. It was also revealed from the result that a similar trend was grasped in hardness increment with the crystallinity of Al-Cu/SiCp AMCs.

Abstract: The camphor-grown pristine carbon nanotubes (CNT) was annealed by a single-stage thermal annealing system through controlled ambient in air, argon and nitrogen, are reported. Field emission scanning electron microscopy images confirmed that the heat treatment process gives a place to re-ordering carbon nanostructures which involves: (i) an elimination of structural defects and (ii) better graphitization of the amorphous carbon phase without damaging CNT structure. The room temperature micro-Raman measurements showed that no significant changes on the D and G-line position. However, different annealing gas ambient could give different values degree of graphitization (ID/IG ratio) due to the nature of gas itself. It reveals that single-stage thermal annealing system is relatively simple and effective to obtain an ideal CNT.

Abstract: The superalloy of Inconel 718 variety is widely used to produce compressor blade in gas turbine engine. The blade tip invariably wears in services and thus requires frequent metallization for repairing. In most commercial Turbine Engine Industries the metallised blades, after grinding, undergo a stress relieving heat treatment at 7600C before return for applications. In this study, the metallised blade is heat treated at different conditions and compared its microstructure and hardness with those of the standard stress relieving treatment blades used in most industries. The microstructure of the stress relieving sample contains dendrite with hardness of 230 HV for the melt zone, 190 HV for the Heat Affected Zone (HAZ) and 420 HV for the parent metal. Solutionising at 982 or 10660C developed hardness less than 220 HV in all sections. By long time ageing treatment of the solutionised sample developed high hardness across the whole blade. These treatments homogenized the microstructure and produced high hardness values by precipitation of secondary phase structures across the blade.

Abstract: Wear is a common problem for engineering components subjected to dynamic loading. Surface modification is mostly applied to reduce the wear. An exploratory research is conducted to form a composite coating on AISI 4340 steel surfaces by incorporating a mixture of TiC and hexagonal Boron Nitride (h-BN) particulates using powder placement and TIG torch melting techniques. Initial results show the evidence of TiC incorporation in all tracks but the presence of h-BN is limited in a few tracks. However, processing conditions are identified that can produce composite coatings incorporating both TiC and h-BN particulates. The melt microstructure consists of a small amount of un-melted TiC and h-BN, partially melted TiC particulates with eutectic structure containing precipitated TiC and TiB2 particles. Hardness of the coating is found to fluctuate along the melt depth. However, the maximum hardness of the coating is about 3 times the base hardness of 250 HV.