Materials Science Forum Vol. 819

Abstract: Reduction of iron oxide by hydrogen is important in the production of direct reduced iron. This method of iron production is gaining increasing significance as an alternative route to the blast furnace technology with the many difficult issues facing the latter, the most important being the problem related to environmental. In order to reduce the emission of greenhouse gases CO₂, particularly for iron making, the production of Direct Reduced Iron (DRI) using hydrogen as the reducing gas instead of carbon monoxide is being considered. Reduction of pure hematite by hydrogen was studied at the laboratory scale, varying the experimental conditions like temperature (700oC and 800oC) and porosity (20% and 40%). Then, a Kinetic Modelling was conducted using Matlab software based on independently measured physical and thermodynamic properties of the reaction system and experimentally measured properties of the reactant solid (Fe₂O₃), gas phase (H₂) and reactant product (Fe). There is a gap that occurs between the predicted result and the experimental result although the model explicated the trend and the behaviour of the reduction rate of Ferric Oxide and indicated a good homogeneity to the experimental conditions used in this research.

Abstract: The aim of this work was to develop understanding of microstructural evolution of the alloy casted in semi-solid condition using a cooling slope and conventional casting followed by ECAP in a 120^o die. Feed materials were prepared by cooling slope casting and conventional casting for ECAP process. The microstructures and Vickers hardness of the worked materials extruded by two routes (A and B_C) were evaluated. The primary α-Al phase tends to be elongated after processing by route A. However, its morphology was similar in nature to the microstructure of the as-cast sample after processing by route B_C. The Si particles become fragmented during ECAP processing and are more nearly globular in shape and uniform in size than in the as-cast sample. The microstructure of the semi-solid cast ECAPed samples was more homogenous than that of the conventional cast ECAPed sample followed by ECAP for both routes. The hardness of semi-solid cast ECAP samples was also higher than that of conventional cast ECAPed samples for both routes.

Abstract: In the production of aluminum alloy strips for packaging industry twin roll strip casting technique is now being extensively employed. The twin roll caster has advantage of the energy saving, low cost equipment and rapid solidification. The present research aimed to investigate the microstructure and hardness of twin roll strip cast aluminum alloys strips by varying the speed of roller cast. Al-Mg-Si ingot was melt in an induction furnace. Once it melted, the liquid was poured into a crucible attached to a twin roller cast to maintain the liquid temperature at 700°C. Molten alloy was poured in the gap between the copper rollers to produce the strips. The rotational speed of the cast rolls was varied from 60-30 rpm. During this process, the melt solidified to form strips. A specimen of 50 mm length cut from the cast strips was subjected to physical and mechanical characterization. Variation in hardness and microstructure of the produced trip were discussed.

Abstract: Annealing treatment is an important step of rolling deformation that contributes to microstructural evolution and leads to the significant changes in damping capacity. Damping capacities were analyzed in the parallel to rolling direction at 1 and 10 Hz respectively. It was found that severe plastic deformation at 40 percent reduction has lower damping capacity compared to that of 30 percent and 20 percent reductions respectively. The microstructural results show that the grains of as rolled alloys were changed to almost equiaxed structures after a rolling reduction at 40 percent reduction.

Abstract: This paper investigated the effect of inoculant, Al-5Ti-1B in conventional and semi-solid casting A356 aluminium alloy. A356 aluminium alloy was melted at 850 oC and poured at 680 °C directly into the steel mould and on the inclined slope into steel mould. Inoculant was added in various percentages of 1 wt.%, 2 wt.%, 3 wt.% and 3.5 wt.% in A356 aluminium alloy melt. Microstructure and microhardness were characterized using optical microscope and Vicker’s microhardness tester. The addition of master alloy up 3.5 wt.% Al-5Ti-1B in conventional casting refined dendritic structure with average grain size of 33.41 μm. The microstructures of semi-solid A356 aluminium alloy with addition of Al-5Ti-1B consist of equiaxed structure of α-Al. Further addition of Al-5Ti-1B refined the globular structure of α-Al. The higher hardness was achieved for A356 alloy prepared using semi-solid with addition of 3.5 wt.% of Al-5Ti-1B.

Abstract: Iron and steelmaking are two of the largest energy intensive industries with the highest growth rate in energy consumption of all energy utilisation sectors. In order to meet the growing greenhouse challenges, incorporation of renewable resources to the existing and emerging metallurgical operation are desirable. In this respect, agricultural wastes can be potentially applied as fuel for ironmaking process to stabilise the greenhouse emissions as it is renewable and CO₂ neutral. Thus, the present study investigates the reduction behavior of iron ore minerals and growth of metallic iron in reduction process. The process was utilized palm shells char (pyrolyzed) as reducing agent at high temperature (1000°C) with inert gas oxygen within 2 hours of reduction reactions. Reducing agent plays a vital role in the reduction process where metallic iron was produced. After the reduction for sample mass ratio of 30:70 palm char over iron ore blend. Metallic iron produced was detected by XRD pattern as well as the other oxides through SEM/EDS analysis. The result indicates that palm shells char can be used as reducing agent by producing metallic iron effectively. The beneficial effect on the environment through decrease use of coke/coal consumption and carbon dioxide emissions in steelmaking process.

Abstract: This work examines the effect of solution heat treatment temperature on the tensile strength of Al-Mg-Si aluminum alloy. All samples were machined according to the ASTM B557. The samples were solution treated at 450°C and 530°C and followed by ageing at 160°C for 0, 5, 10, 15 and 20 hours. Tensile test was carried out on the samples after heat treatment. The results showed that the highest tensile strengths (201.69 MPa) was given by the sample solution heat treated at 530 °C for 5 hours followed by 20 hours aging at 160 °C. Whereas, the lowest tensile strength (98.52MPa) was given by the sample solution treated at 450°C for 20 hours. Tensile strength was increased with ageing process and decreased for over-aged samples.

Abstract: The effect of welding current on the joining of mild steel and aluminum 6063 has been investigated. The joining was carried using a tungsten inert gas (TIG) welding. The welding currents used were 30 A to 80 A. The formation of intermetallic reaction layers (IML) and tensile shear strength of the joining were investigated. The result showed that tensile shear strength increased as welding current increased up to 55 A. Microstructural analysis showed that intermetallic reaction layer was formed at the interface between steel and aluminum alloy during welding process. The thickness of IML was decreased with decreasing welding current.

Abstract: The influence of heat treatment condition with addition of zirconium on the some properties of aluminum alloy has been investigated. The composition of aluminum alloy cast produce from this research was supplied from the foundry. The cast alloys were given a solutionizing treatment at 520°C followed by artificial aging at 175°C for a different period of time up to 10 hours. Hardness of heat treated aluminum alloy then were determined by comparing to the as cast and natural aging alloy. The addition of zirconium will improve the properties of the alloy in term of hardness and conductivity. Grain size of alloy has no significant effect when aging time increased together with zirconium addition.