Hazman Seli

Bio: Hazman Seli is an academic researcher from Universiti Teknologi MARA. The author has contributed to research in topics: Friction welding & Heat-affected zone. The author has an hindex of 5, co-authored 12 publications receiving 130 citations. Previous affiliations of Hazman Seli include Universiti Sains Malaysia.

Mechanical evaluation and thermal modelling of friction welding of mild steel and aluminium

Abstract: In friction welding of two dissimilar materials, two rods are welded together by holding one of them still while rotating the other under the influence of an axial load which creates frictional heat in the interface. In this study, mechanical properties of mild steel and aluminium welded rods were evaluated to understand the thermal effects, and an explicit one-dimensional finite difference method was used to approximate the heating and cooling temperature distribution of the joint. The thermal effects of the friction welding were observed to have lowered the welded materials hardness compared to the parent materials. The tensile strength of the welded rods is lower than the parent rods due to incomplete welding. The preliminary predictions were compared to actual thermocouple data from welds conducted under identical conditions and were shown to be in fair agreement. The finite difference method proposed in this work will provide guidance in weld parameter development and will allow better understanding of the friction welding process.

Evaluation of properties and FEM Model of the Friction welded mild Steel-Al6061-Alumina

Abstract: Evaluation of mechanical and interfacial properties of friction welded alumina-mild steel rods with the use of Al6061 sheet are presented in this work. SEM, EDX analysis, hardness and bending strength tests were conducted. The bonds were attained through interfacial interlocking and intermetalllic phase formation with average bending strengths in the range of 40 to 200 MPa and insignificant hardness change in the parent alumina and mild steel. A preliminary simulation was made to predict the deformation, stress, strain and temperature distribution during the joining operation using a fully coupled thermo-mechanical FE model. The aluminum alloy metal being rubbed was simulated using a phenomenological Johnson-Cook viscoplasticity material model, which suited for materials subjected to large strains, high strain rates and high temperatures. The highest stress, strain and deformation are found to be within the heat affected zone of the weld close to the periphery rubbing surface region and correspond to the highest temperature profiles observed.

Characterization and thermal modelling of friction welded alumina–mild steel with the use of Al 1100 interlayer

Abstract: This paper reports a study of the physical and thermal behaviors of friction welded alumina–mild steel rods with the use of AL 1100 sheet as interlayer. A series of hardness tests, bending tests, macrostructure observations, SEM and EDX analyses were carried out and were combined with a finite difference thermal model to acquire material parameters. This work demonstrated the insignificant change in the hardness value of the parent alumina and the slight increase in hardness value of the parent mild steel, particularly near the interface region. The bending strength increased with the increase of friction times with the highest bending strength obtained was 186 MPa at 20 s. The fractured surface shows the strong bond at the middle of the interface. The bond was obtained through interfacial interlocking and narrow intermetallic phase formation. However, the incomplete joint observed was detrimental to the joint strength. The thermal profile predictions were compared to actual thermocouple data from welds conducted under identical conditions and were shown to be in fair agreement. Even though the FD method proposed in this study cannot replace a more accurate numerical analysis, it does provide guidance in weld parameter development and allows better understanding of the friction welding process.

Sago pith waste ash as a potential raw material for ceramic and geopolymer fabrication

Abstract: This study focuses on the potential usage of sago pith waste ash (SPWA) obtained from sago pith waste (SPW) calcined from 500 to 1000 °C. SPWA was characterized by TGA/DTA, XRD, XRF, FTIR, and FESEM incorporating with EDX. About 4% of SPWA was generated from each tonne of SPW at 700 °C as the optimum calcination temperature as indicated by thermal analysis. The phases found in SPWA at calcination temperatures of less than 800 °C are quartz, calcite, and magnesite. XRF analysis found that SPWA was mainly composed of CaO and SiO2 with the presence of other oxides such as MgO, Fe2O3, and Al2O3. Both CaO and SiO2 are very significant oxides as they can be used as an alternative binder for the synthesis of geopolymer products, especially in combination with other ashes such as fly ash (FA). Geopolymers fabricated from FA partially substituted with SPWA showed a 5% increase in compressive strength. Therefore, the benefits of SPWA are twofold: first, as a resource of renewable energy generated through the burning of SPW which can be utilized by related industries, and second, SPWA itself becomes a potential raw material for the production of ceramic and geopolymer products.

Aeration Leaching of Iron from Nitrided Malaysian Ilmenite Reduced by Polystyrene-Coal Reductant☆

Abstract: In this study, aeration leaching process of iron (Fe) from titanium oxycarbonitride (TiOxCyNz) produced by carbothermal reduction and nitridation of Malaysian ilmenite, in ammonium chloride (NH4Cl) solution was investigated. The reductant used for this study was a blend of Polystyrene (PS) and Mukah-Balingan coal from Sarawak and reduction temperature was 1200 °C. Phase composition of reduced sample was analyzed using X-Ray Diffraction (XRD) and SEM/EDX. The leaching experiment was carried out for 4-6 hours. The final solid sample was analyzed by XRD and SEM/EDX analysis while the filtered solution was analyzed by ICP-OES. Design of Experiment (DOE) analysis was used to find out the optimum condition for the leaching of metallic Fe in NH4Cl solution. In this study, a full factorial design model was used to detect the interaction between the three parameters. A fully randomized factorial design, with various combinations of PS/Coal (C) weight ratio, leaching time, and amount of catalyst added was investigated. It was observed that the leaching time was the most important factor affecting the amount of Ti and Fe extracted. The results of the design showed that the percentage of Fe extracted reached up to 76.85% at leaching time of 6 hours, at PS/C ratio of 0.18 and using 1 wt.% of glucose catalyst.

Joining of dissimilar materials

Abstract: Emerging trends in manufacturing such as light weighting, increased performance and functionality increases the use of multi-material, hybrid structures and thus the need for joining of dissimilar materials. The properties of the different materials are jointly utilised to achieve product performance. The joining processes can, on the other hand be challenging due to the same different properties. This paper reviews and summarizes state of the art research in joining dissimilar materials. Current and emerging joining technologies are reviewed according to the mechanisms of joint formation, i.e.; mechanical, chemical, thermal, or hybrid processes. Methods for process selection are described and future challenges for research on joining dissimilar materials are summarized.

Clays and bodies for ceramic tiles: Reappraisal and technological classification

Abstract: The ceramic tile industry is a dynamic sector whose technological innovation and market trends have drawn a complex picture of products and processes. Raw materials have been deeply involved in such an evolution: the flexibility of current manufacturing cycles enables the use of a very wide range of clays, whose chemical and mineralogical composition, particle size distribution and ceramic properties were reappraised. The classical reference schemes are no longer able to properly describe and predict the role of clays in tilemaking. In order to fill this gap, an industry-oriented, technological classification of clay raw materials is proposed on the basis of chemical (Fe2O3 content) and mineralogical parameters (amount of phyllosilicates and carbonates) together with particle size (fractions 63 μm) and plasticity (methylene blue index and Atterberg plastic index). It firstly discriminates light-firing and dark-firing clays according to an iron oxide threshold of 3%. Light-firing clays are distinguished by the amount of kaolinite group minerals and plasticity in “kaolins” (high-grade, low-grade, and raw kaolins, kaolinitic loams) and “plastic clays” (ball clays, pyrophyllitic clays, white bentonites); the distinction of three classes of ball clays with increasing plasticity is envisaged. Dark-firing clays are classified according to coarse-grained fraction and amount of carbonates in carbonate-rich types (marly and carbonatic clays), red loams and red clays; these latter are furtherly differentiated by the relative abundance of clay minerals. Such a classification is essential to draw the guidelines for body formulation and to explain the criteria followed in the industrial practice for each category of ceramic tiles. Key properties are discussed to design batches for porous tiles, vitrified and semi-vitrified red stoneware, and vitrified light-firing bodies. Both the clay classification and the guidelines to body formulation are intended to provide up-to-date tools to assess the ceramic potential and correct use in tilemaking of clay materials, but they cannot substitute a throroughful technological characterization, adequately simulating the industrial processing.

Properties of Friction Welding Titanium-stainless Steel Joints with a Nickel Interlayer

Abstract: The probability and appropriate processing parameters of friction welding method of commercially pure titanium to a 304L stainless steel with an electroplated nickel interlayer have been investigated. The microstructure of the welded joints has been observed by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, and the main factors affecting friction welding process were analysed. Metallographic analysis revealed that a good bonding was obtained at both the titanium/nickel and nickel/stainless steel interfaces, and the diffusion products were identified in the weld zone. The effect of friction time and forging pressure on metallurgical and mechanical properties were evaluated. The results showed that atom diffused well and no presence of Fe–Ti intermetallic compounds appeared at optimum parameters. With the increment of friction time, the thermal degradation region increasing hence the thickness of interlayer material is decreasing. Microhardness test across the joining interfaces demonstrated the effect of solid solution hardening in the weld zone. The tensile strength increased with increasing forging pressure at constant friction time. Tensile test showed that the maximum average tensile strength of ∼289 MPa was obtained for the joint welded at forging pressure of 320 MPa. The tensile fracture surfaces are indicating river patterns of brittle mode of failure of the joints. The tensile fracture of the welded joint occurred in titanium side near the interface.

Effects of resistance spot welding parameters on microstructures and mechanical properties of dissimilar material joints of galvanised high strength steel and aluminium alloy

Abstract: Intermediate frequency resistance spot welding has been adopted to join dissimilar materials of H220YD galvanised high strength steel and 6008 aluminium alloy. The effects of welding current and welding time on microstructures and mechanical properties of the welded joints were investigated. A thin intermetallic compound layer composed of Fe2Al5 phase and Fe4Al13 phase formed at the steel/aluminium interface. The interfacial intermetallic compound layer has higher nanohardness compared with the aluminium alloy nugget and galvanised steel. With increasing welding current (4–11 kA) and welding time (50–300 ms), the nugget diameter increased, the interfacial layer structure became coarser and the tensile shear load of the welded joints had an increased tendency. The maximum tensile shear load reached 3309 N at 9 kA for 250 ms. Crack initiated at the interfacial intermetallic compound layer of the tensile shear specimens, then propagated through the interfacial layer principally, and meantime through the alum...

Mechanical property and microstructure of aluminum alloy-steel tubes joint by magnetic pulse welding

Abstract: The mechanical properties, microstructure and interface pattern of lapped joint of AA3003-O and steel 20 tubes by magnetic pulse welding (MPW) were investigated. The results show that the tension and torsion strength values are higher than that of the aluminum tube when the discharge voltage of MPW process is not less than 8 kV. The metallurgical joint, which composes of interfaces, non-uniform transition zone and basic metals, are obtained under discharge voltage of 15 kV, the preset oblique angle of 4° and radial gap of 1.2–1.4 mm. High-density dislocations and nanocrystals present in basic metals along the interfaces. The transition zone has the highest micro-hardness of 5.1 GPa. The multi-direction micro-cracks and the micro-apertures characterize the transition zone of MPW joint. The mutual diffusion of Fe and Al elements occurs in the transition zone, where content of Al element is higher than Fe element besides a narrow region close to the interface of steel and zone. The narrower transition zone presents more even distribution of basic elements than the wider one.