Advanced Materials Research Vol. 1024

Abstract: Surface modification by means of alloying is a vital process to improve the performance of a material surface which is subjected to wear and corrosion environments without altering the bulk properties. In this study, the surface of commercial purity-titanium (CP-Ti) material was alloyed using pre-placed powder mixture of iron, silicon and carbon at different weight ratios under TIG torch melting technique. The effects of energy input (1080 and 1350 J/mm) in TIG torch on the melt geometry, topography, microstructure and hardness were examined. The results showed that the TIG torch produced melt pools geometry with hemispherical in shape and different geometrical dimensions. Pores were seen to be concentrated at the edges where low melting energies are prominent to entrapped escaped gases upon fast melt solidification. The melt layers with the 1350 J/mm consisted of armed typed of TiC precipitation in the presence of longer solidification time. The sizes of dendrites observed at energy inputs of 1350 J/mm was found to be greater in population and larger in the middle of the melt pool compared to the energy input of 1080 J/mm. The alloyed layer exhibited a maximum hardness of ~ 810 HV which is about 4 times greater than the base hardness of 200 HV. The high hardness observed at particular areas is attributed to the higher population and larger sizes of dendritic microstructure produced using 1350 J/mm TIG arc source compared to 1080 J/mm which was dominated by lesser precipitated TiC resulting lower hardness values in the melt pool. Keywords: Surface modification; TiC; TIG; dendrites; microhardness

Abstract: The increasing production of steel leads to an increment of solid wastes generated especially Electric Arc Furnace (EAF) slag. This becomes a serious concern as the slag has to be disposed in a proper manner in order to avoid dumping in landfills which will eventually occupy available land and may cause permanent damage to the flora and fauna. In this project, an attempt was made to utilize the EAF slag as one of the raw materials in ceramic tiles. Results obtained showed that as percentage of EAF slag added was increased up to 60%, percentage of apparent porosity and water absorption were found to increase, accompanied by reduction in flexural strength due to more severe porosity was observed in the tiles. On the other hand, reducing the percentage of EAF slag up to 40% while increasing percentage of ball clay added led to formation of higher total percentage of anortite and wollastonite minerals. This would contribute to higher flexural strength of tiles. In addition, by adding silica and feldspar, the flexural strength of tile produced was further improved due to optimization of densification process. Highest flexural strength of EAF slag based tiles was attained at composition of 40% EAF slag 30% ball clay 10% feldspar 20% silica. It was observed that properties of ceramic tiles added with EAF slag, especially flexural strength are comparable with commercial ceramic tiles. Therefore, the EAF slag ceramic tiles have great potential to be made into high flexural strength or wear resistant floor tiles.

Abstract: This paper presents laser surface modification of gray cast iron for enhanced surface hardness properties. A 300 W high power Nd:YAG laser system with pulse mode was used to modify gray cast iron samples surface. Laser processing was conducted using a 3³ full factorial design. Three controlled parameters were laser power, pulse duration and overlap percentage. The modified surface was characterised for metallographic study, roughness and hardness. Metallographic study and surface morphology were conducted using optical microscope while hardness properties were measured using Vickers scale. Surface roughness was measured using a 2D stylus profilometer. The results show that hardness of laser modified surface increased due to grain refinement. The overlapping rates increased significantly with decreasing laser scanning speed which affected sample surface integrity. Low surface roughness obtained at the highest scanning speed of 1400 mm/min, and low power of 830 W with pulse repetition frequency of 50 Hz. Process optimization was carried out for maximum surface hardness and laser modified depth, and minimum surface roughness. These findings indicate potential application of cast iron for high wear resistant applications through laser surface modification.

Abstract: Equal Channel Angular Pressing (ECAP) is one of Severe Plastic Deformation (SPD) methods used to produce ultra-fine grains. In this study, aluminum alloy 6061 in a rod shape as a result from casting process was used in the experiment. The rod samples were then subjected to ECAP, up to 3 passes, through Bc route. The die channel angle of the ECAP is 120⁰. The changes in the microstructure and mechanical properties of the samples deformed by 1-pass, 2-pass, and 3-pass of ECAP were investigated. The results show that as number of ECAP passes increase, the applied strain accumulated in the samples also increases and the grains change from equiaxed to elongated structure. The hardness is proportional to the number of ECAP passes, and the highest value is 107 HV for 3 passes with strain value of 2.0.

Abstract: This Paper Reports the Microstructure, IMC Evaluation and Wettability of Low-Ag Sn-Ag-Cu(SAC) (0.3 Wt% Ag and 0.5 Wt% Ag) and SAC305 Solder Alloys in Reflowed and Agedconditions. Reflow was Done at 250°C and Thermal Aging at 150°C For100 Hours. Microstructure of Bulk Solder and the IMC Formed at Interfacebetween Solder and Cu Substrate were Observed Using SEM Equipped with EDX. Microstructureobservation Showed Finer β-Sn Dendrites at 0.3%Ag Indicating a Possiblerefining Effect of Lower Ag on Bulk Solder Microstructure. SEM Result Showedfiner Ag₃Sn Distributed in the Solder but the IMC Thickness of Bothreflowed and Aged Solder Joint Seems to Increase with Decreasing Ag Content.This could be due to Finer β-Sn Dendrites which Provide more Diffusion Paththrough Grain Boundaries and Increase IMC Thickness. Similarly, Lower Ag Content Appears to have Detrimental Effect on Wettability and Wetting Angle Ofsolder Joint.

Abstract: This paper presents a development of a composite using friction stir process of AA606-T6 aluminum alloy reinforced with amorphous silica obtained from rice husk ash. The amorphous silica was produced after acid leaching and calcinations at 500°C. The silica powder was placed into a groove made in the joining line of AA606-T6 plates prior to friction stir process. Hard silica particles restricted the grain growth of aluminum matrix that contributed to a slight increase in hardness. Hardness decreases in zones under the tool was observed because AA6061-T6 alloy was sensitive to friction heat generated by the tool. Ageing at 200°C increased the hardness of the aluminum in the friction stir process zones.

Abstract: Twin roll casting is an innovative route to produce thin metal strip directly from the melt. In this paper, solidification characteristics in roll strip cast aluminum alloys is described. Al-Mg-Si alloy was melted in a crucible and poured to stainless steel roller. The roll was connected to a driving motor which the rotation speed can vary from 10 rpm to 100 rpm. During this process, the melt was solidified to form a strip. A specimen of 50mm was cut from the cast strips. The strip was characterized for the thickness, hardness and microstructure. Variation in hardness, microstructure of the produced trip is explained as a comparison to normal casting.

Abstract: Electric arc furnace slag (EAFS) is a solid waste from steel making industrial. Previously, EAFS was deposited, recycled or used as fertilizer. In present study, EAFS is used as one of the raw materials in ceramic tile production. EAFS added tiles samples have been prepared by mixing of EAFS with ball clay, quartz and feldspar. The feldspar content was varied at various weight percentages (0, 10 and 20 %) to observe their effect on the produced samples. The raw materials mixture was pressed and then sintered at temperature range 1100°C-1175°C for 1 hour. In general, results shows that, sample with higher content of feldspar require shorter vitrification range and having relatively higher density and good strength properties. In addition, MOR value was increasing as the sintering temperature was increasing. However when the temperature reached 1175°C, the MOR was dropped which may be due to the early vitrification of the compositions, resulting in over firing, grain growth and recrystallization. Whereas the density values are relatively higher than the conventional vitreous ceramic tiles due to the presence of high amount of iron oxide from the EAFS.

Abstract: In this study, WC-stainless steel AISI 347 hardmetal system was produced to replace WC-Co hardmetal which uses the expensive, toxic and depleted resource Co. WC, stainless steel AISI 347 and graphite powder mixture were milled in a planetary mill under argon atmosphere using a stainless steel container and balls. Carbon was added in amounts ranging from 0 wt% until 4 wt% into the composition to avoid unwanted η (Fe₃W₃C) phase. As-milled powder was compacted at 300 MPa and sintered in a tube furnace at 1350°C. ɳ phase was detected in compositions with 0 and 1 wt% C addition. For 2 wt% C addition, no η (Fe₃W₃C) phase formation was identified. However, the η phase was detected for compositions containing 3 and 4 wt% C. Maximum hardness was achieved due to the absence of η phase.

Abstract: This paper presents optimisation of hot press forming using design of experiment for high hardness properties at maximum cooling water temperature and minimum quenching time. Samples were boron steel blanks of 60x50 mm dimension. Hot press forming was conducted using a hydraulic press machine with 20 tonne maximum load. Results of this research work show that parameters obtained by single response optimization through desirability analysis route will increase hardness by 66.72%. The hardness properties of samples were between 477 and 551.4 HV _(0.1). These findings were important to design tailored ultra-high strength automotive components at different process parameter settings and to reduce production cost consumption and improve production rate.