Key Engineering Materials Vol. 987

Abstract: The microstructure evolution during the extrusion process of AA6XXX aluminum alloys is getting a significant interest from extruders and researchers because of the effect of the grain structure on the extruded component properties. Several process and material parameters such as chemical composition, homogenization, temperature evolution, extrusion speed, geometries and quenching have a direct impact on the final grain size of extruded profiles. Because there are so many affecting elements, it is extremely challenging to forecast the microstructure evolution and, as a result, research activities are still required to understand and control the aluminum alloy recrystallization behaviour. In this work, a methodology for the microstructural characterization of AA6XXX aluminum alloys is proposed. The methodology involves the experimental investigation of the profile grain evolution during the extrusion process, the development of a AA6XXX recrystallization model optimized to describe the AA6063 recrystallization behaviour and the simulation by means of finite element method of the final microstructure of the extruded profile.

Abstract: Nitrogen cooling has been identified as a powerful industrial solution for the hot extrusion process to remove heat in the die and in the profile. The complexity involved in the design of cooling channels depends on many factors, including the cooling path, its position with respect to the hottest zones as well as the nitrogen phase change that strongly affects the heat removal capacity. However, the industrial approach is still stuck in the empirical and based-experience practices that too often strongly limit the possibilities of obtaining a performing cooling solution. In this context, this work intends to summarize and discuss the advanced recent trends in the design of cooling channels for extrusion dies proposed by the authors based on the numerical approaches, with the final aim to propose possible solutions to fill the current gaps of the suboptimal industrial approaches.

Abstract: The velocity fields of axisymmetric direct extrusion of metals was analysed by the upper-bound method and compared with the results from the finite-volume method, FVM. The upper-bound technique proposed by Avitzur and by Zhao et al. together with the streamline functions were employed to calculate the analytical velocity fields, which consider the friction at die wall. Moreover, the components of strain-rate are also presented. Additionally, the axisymmetric extrusion process was modelled by the FVM method to calculate the velocity fields and compared with the Avitzur’s and by Zhao’s solutions. The FVM velocity fields were calculated by using the Eulerian approach of fixed grid, the governing equations of metal plastic flow and conservation laws discretized by the FVM and the Explicit MacCormack method in structured and collocated mesh were also employed. Friction at die wall was modelled by the friction factor model, using the tangential shear stress boundary conditions. The examined material experimental parameters were obtained from the Al 6351 aluminium alloy in the direct extrusion process at 450^o C. Velocity fields of the longitudinal and radial velocity distributions by the upper-bound and FVM methods are presented and compared. Good agreement is shown between the radial velocity component V_r from the Avitzur´s and FVM results, but poor for the longitudinal velocity V_z. From the analysis of velocity fields, the most severe condition of wear on the inner wall of the die and material surface damage occurs in the area near the exit corner of the die. However, the predicted location of the severe wear region in the die wall by the FVM method is located prior to the point predicted by the Avitzur model.

Abstract: The paper presents the experience of development and implementation of an integrated approach of extrusion simulation with the automated design of the dies as a new way to speed up the technology development and its optimisation based on the QForm UK Extrusion simulation program and QForm Extrusion Die Designer (QExDD) design system. Bearing and prechamber optimisation types are considered for the porthole design. Welding quality and possible streaking lines in the profile are analysed for the tool construction with optimised prechamber contour.

Abstract: This paper focused on lateral trochanteric wall stress which is a contributing factor for the success of complex trochanteric fracture management with loss of medical bone support. Its aim was to assess performance of augmented fixations to Dynamic Hip Screw (DHS). The analysis was performed using Finite Element (FE) method, where the femoral bone and fixations were developed from reverse engineering technique. The boundary conditions were physiological loads with constraints at distal condyle. It was revealed that lateral augmented fixation i.e. trochanteric stabilization plate raised the trochanteric lateral wall stress that could be at risk of bone breakage.

Abstract: This study aims to represent an approach for transferring the materials testing datasets to the digital schema that meets the prerequisites of the semantic web. As a use case, the tensile stress relaxation testing method was evaluated and the testing datasets for several copper alloys were prepared. The tensile stress relaxation testing ontology (TSRTO) was modeled following the test standard requirements and by utilizing the appropriate upper-level ontologies. Eventually, mapping the testing datasets into the knowledge graph and converting the data-mapped graphs to the machine-readable Resource Description Framework (RDF) schema led to the preparation of the digital version of testing data which can be efficiently queried on the web.

Abstract: Cocoa husks, usually discarded as waste, possess valuable biomass that can be utilized. The objective of this research is to study the properties of charcoal obtained from the carbonization of leftover cocoa husks in the Suratthani province, Thailand. The discarded cocoa husks were carbonized in a designed charcoal kiln, and the carbonization temperature was investigated. It was found that the carbonization process had four phases, with a total duration of approximately 3.5 hours. The maximum temperature reached during carbonization was around 470 °C, and the average ignition temperature of the charcoal from cocoa husks in this research was approximately 261.1 °C. Heat analysis of the charcoal revealed a thermal conductivity of about 4678 kcal/kg. Additionally, a morphological analysis of the charcoal from cocoa husks showed higher porosity compared to dried cocoa husks. Therefore, charcoal from cocoa husks has the potential to be used in value-added products such as charcoal briquettes and odor-absorbing materials.

Abstract: In this study, the blast furnace slag (BFS) was used to replace 30% cement (weight replacement), freshwater, and saltwater (half, same, and twice the concentration of seawater) used to produce the cement mortar. Then, these four types of mixing water were used to cure the mortar till the test ages (7 days and 28 days). The test results show that, at 7 days, the compressive strength of saltwater (half concentration) mixing and curing mortar incorporating BFS is the highest (78 MPa). The freshwater mixing and curing control mortar has the lowest compressive strength (36.2 MPa). At 28 days, the compressive strength of saltwater (twice concentration) mixing and saltwater (half concentration) curing mortar incorporating BFS is the highest (90.2MPa). The strength of the control mortar is 53.0MPa under the same curing water, which is still relatively low. It can be seen from this that the mixing and curing of saltwater are beneficial to improving the compressive strength of cement mortar. The freshwater mixing and saltwater (twice concentration) curing cement mortar incorporating 30% BFS can have a higher strength at 28 days.

Abstract: This paper aims to valorize waste materials for producing eco-friendly fired clay tiles. Green glass cullet and the water supply process waste; sediment soil have been utilized. In addition, local white clay is used to mix with waste materials for promoting the plasticity and easily forming of specimens. The Triaxial diagram has been employed to construct the formulas. Mixture’s formulation of this experiment consists of 23 formulas. Test samples are fired at temperature 950 °C. Physical properties of fired specimens are carried out and compared with Thailand Industrial Standards. The results show that formula A6 can pass TIS. 2508-2555 wall tiles of medium water absorption series. However, A6 only utilize 10% of sediment soil. Therefore, increasing sintering temperature to 1,050 °C for utilizing higher content of sediment soil has been examined. Twelve formulas of group A and C are selected to be further investigated. Results show that formula A6 and C6 can achieve TIS. 2508-2555. Formula C6 utilizing 30% and 60% of sediment soil and green glass cullet obtain the highest strength and lowest water absorption. Analyzing microstructure of this formula by Scanning Electron Microscope has found glassy phases. Furthermore, Wollastonite 2M, Nepheline and Albite are identified by X-Ray Diffractometer. It can be summarized that sediment soil mixed up with green glass cullet and local white clay can develop brownish green color fired clay tiles which can be further applied to the production of local ceramic factory.