Papers by Keyword: Microstructure

Abstract: Despite growing interest in geopolymers-graphene oxide (GO) composites for energy-responsive construction materials, quantitative correlations between thermoelectric performance, thermal properties, density, and mechanical behavior remain limited, and the optimal GO loading that balances multifunctional performance has not been clearly established. In this study, fly ash–based geopolymer composites incorporating GO (0-2 g) were systematically investigated to elucidate thermoelectric, microstructural, and mechanical responses. The results show that moderate GO incorporation establishes conductive networks that improve both charge and heat transfer while enhancing matrix densification and interfacial bonding. Significant increases in the Seebeck coefficient and thermoelectric voltage were observed, suggesting improved charge-carrier transport and thermoelectric conversion efficiency. SEM-EDS images showed a denser, more homogeneous matrix with reduced porosity, while mechanical tests revealed greater toughness and ductility due to crack-bridging and nanosheet pull-out mechanisms. In contrast, excessive GO addition caused agglomeration and reduced matrix cohesion. The GO incorporation significantly enhances thermal conductivity and Seebeck coefficient, indicating improved heat and charge transport through conductive GO networks. Consequently, the thermoelectric figure of merit (ZT) increased nearly fourfold. Conversely, the specific heat capacity (C_p) slightly decreased, reflecting reduced lattice heat storage due to matrix densification. The optimal GO content (approximately 1 g) achieved the best balance between mechanical integrity and thermal–electrical performance. These findings establish clear structure-property-performance relationships and demonstrate the potential of GO-modified geopolymers as multifunctional and energy-responsive materials for advanced construction and thermoelectric applications.

Abstract: Zinc-aluminum (Zn-Al) alloys are widely applied in engineering due to their strength, corrosion resistance, and castability. Among them, ZA-12 (hypereutectic) offers microstructural characteristics distinct from Zamak 5 (hypoeutectic), yet its response to microalloying has not been fully characterized. In this study, ZA-12 was produced by green sand casting and evaluated before and after titanium-boron (Ti-B) microalloying to examine changes in mechanical and microstructural behavior. Compression testing and hardness measurements were performed alongside grain size analysis to assess the influence of Ti-B additions. The results show that Ti-B treatment refines the microstructure of ZA-12 and produces measurable variations in hardness and compressive strength. When compared with previously characterized green sand-cast Zamak 5, ZA-12 displays noticeable differences in the extent of property changes under Ti-B addition, reflecting the influence of alloy composition and solidification type. This comparative assessment contributes to a better understanding of how hypereutectic and hypoeutectic Zn-Al alloys respond to Ti-B microalloying and supports ongoing efforts to tailor these alloys for engineering applications.

Abstract: This study investigates the hot deformation behavior of a near-β TC18 titanium alloy at 750 °C, with a focus on the interplay between dynamic softening mechanisms and α/β phase transformation. Compression tests were conducted at varying strain rates (0.01–1 s^-1) and true strains (40% to 80%). The results show that increasing strain rate and deformation promote dislocation accumulation, which leads to enhanced stored energy. This drives a transform from dynamic recovery (DRV) to dynamic recrystallization (DRX) as the dominant softening mechanism and concurrently accelerates dynamic phase transformation. Meanwhile, intensified α-phase spheroidization is also observed.The strong coupling between DRX and phase transformation contributes to microstructural refinement, ultimately improving mechanical properties by balancing strength and ductility. These findings provide new insights into deformation mechanisms and offer guidance for optimizing thermomechanical processing of near-β titanium alloys.

Abstract: The tribological behavior of an aluminum metal matrix composite with TiC particles was investigated in this study. Composite specimens were prepared using the stir casting method, with the weight percentage of TiC particles with 2.5% Experiments were designed employing the Taguchi technique, with applied load, sliding velocity and sliding distance considered as control parameters with varying levels. Wear rate and coefficient of friction were determined using a Magnum pin-on-disc machine. ANOVA was then applied to assess the impact of each factor on wear rate and coefficient of friction. The results showed a significant effect of TiC reinforcement weight percentage on both specific wear rate and coefficient of friction. Increasing TiC reinforcement led to enhanced wear resistance of the composite material. Mathematical models were subsequently developed via regression to predict specific wear rate and coefficient of friction.

Abstract: In this study, monolithic samples and 3% SiCp/6061 composite samples were fabricated using spark plasma sintering. A comparative analysis of the microstructure, ageing response, and mechanical properties of these materials revealed that the addition of SiCp induced thermal mismatch dislocations, which accelerated the ageing kinetics. As a result, the time required to reach peak ageing decreased from 8.5 hours to 8 hours, and the peak ageing hardness increased from 102.7 HV to 113.5 HV. The tensile strength of the peak-aged composite sample improved from 315.5 MPa to 352.4 MPa, while the elongation decreased from 11.8% to 8.8%. These findings provide valuable insights for optimizing the properties of the composite, ultimately enhancing its performance and applicability in demanding engineering applications.

Abstract: In this present work, a newly emerging manufacturing process, namely metal additive manufacturing, is discussed in detail. The review work considers articles that describe the impact of ultrasonic vibration assistance on the laser-based Directed Energy Deposition (LP-DED) process, a promising approach in metal additive manufacturing. The incorporation of high-frequency ultrasonic vibrations during deposition enhances melt pool dynamics, promotes refined grain structures, and significantly reduces the formation of porosity and residual stress. Ultrasonic-assisted DED contributes to improved interlayer bonding, uniform particle dispersion, and enhanced mechanical properties of the printed part. Results indicate that this hybrid approach can optimise deposition quality and mechanical performance, making it suitable for critical applications across aerospace, biomedical, and energy sectors. The findings highlight ultrasonic assistance as a valuable tool for overcoming key challenges in conventional DED processes.

Abstract: In this experiment, nano-sucralfate for gastric mucosa protection was prepared by the pyridine method using sucrose, sulfuric acid and aluminum powder as raw materials. The product was characterized by Fourier transform infrared spectrometer (FTIR), thermogravimetric analyzer (TGA) and its surface micro-morphology was observed by scanning electron microscope (SEM).. Infrared spectroscopy and thermogravimetric analysis explored the physical and chemical properties of sucralfate, providing specific data support for its practical application. SEM images showed that sucralfate particles had a porous flower-like structure with high porosity. In addition, the synthesized product has high purity and good thermal stability, which play an important role in improving its protective effect on gastric mucosa.

Abstract: A cold roll-bonding (CRB) process is applied to fabricate a multi-layer Al sheet using AA5052 and AA6061 alloys. The rolling is performed for four-layer sheets in which AA5052 and AA6061 sheets are stacked alternately after surface treatments such as degreasing and wire brushing. The 4-layer sheets with a thickness of 8 mm were roll-bonded to 2 mm by rolling at total reduction of 75%. The as roll-bonded Al sheets are then processed by natural aging (T4) and artificial aging (T6) treatments. T4 and T6 treated specimens showed a typical recrystallization structure over all regions of AA5052 and AA6061. The average grain diameter of T4 and T6 specimens was about 15 μm, which is almost the same. In addition, the Al sheet showed a heterogeneous hardness distribution in thickness direction. After the aging treatments of T4 and T6, the strength rather decreased and the elongation increased. It is found that new multilayer Al sheets made of AA6061 and AA5052 alloys, exhibiting various mechanical properties can be fabricated through the CRB and subsequent aging treatments.

Abstract: This article aims to review the recent advances in the laser powder bed fusion process (L-PBF) of H13 tool steel for the dies used in the high pressure die casting (HPDC) applications. The effect of processing variables is briefly reviewed for the evolution of microstructure (phase transformations, as-built microstructure and carbides precipitation), mechanical properties, and defects. The second part of the review is focused on conformal cooling applications to HPDC dies, which is critical for die life and productivity. Achieving better microstructure without defects, understanding the role of processing variables in L-PBF and their interdependencies remains the key challenge for the as-built part, while the benefits of preheating and post-heat treatments are evident. Significant benefits are realized in the applications of die inserts favoring lower die surface temperature, reduced cycle time and lubrication, and thermo-mechanical stresses. In addition, L-PBF also plays a key role in die remanufacturing where significant benefits are achieved in terms of materials savings and improved performance compared to traditional repair technologies. Overall, L-PBF offers a transformative pathway for high-performance HPDC dies; however, most investigations are trial-based. Long-term studies are needed for performance assessment and establishing failure mechanisms in production environments.

Abstract: High-strength and recycling tolerable aluminum alloys make a significant contribution to weight reduction in modern lightweight construction. The advantages of aluminum alloys in terms of their low density combined with high strength can be significantly improved by the alloy composition. In contrast to the conventionally established process route, high-magnesium alloys can be produced using the twin-roll strip casting process. This allows additional process steps such as hot rolling and annealing to be drastically reduced in the economical production of near-net-shape strips, saving emissions and energy consumption. The strip casting process has already been applied to numerous aluminum alloys and enables their production, although the understanding of advanced alloys in this area is not yet fully understood because of its limited production in industry-related research due to the complexity of the process. However, transferring the high strength generated during rapid solidification into usable sheet performance remains challenging, especially at elevated Mg contents, where segregation, casting-related defects, and solute-affected recrystallization can limit ductility and processability. This study investigates the potential of a high-magnesium aluminum alloy produced by vertical strip casting. The properties of the alloy are correlated with the microstructural and mechanical characteristics and developed on the basis of an industrial reference alloy. For this purpose, an EN AW 5182 and an AlMg10 alloy were processed. The results show that high-magnesium alloys can be produced and processed using strip casting. In terms of the high-magnesium alloy, improved results can be achieved compared to the industrial EN AW 5182 alloy. Key findings: The strength of high-magnesium alloy is significantly above those of the EN-AW 5182 after strip casting enabling nearly 600 N/mm² tensile strength, but the final properties are below this potentially possible characteristic after strip casting, presumably due to non-ideal recrystallization and an insufficiently adapted process route including rolling and annealing parameters.