Papers by Keyword: Microstructure

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.

Abstract: Understanding the relationships between microstructure and (mechanical) properties is inevitable for the design of modern structural metallic materials. A crucial property for most high-strength steels is ductile damage tolerance, since ductile damage can accumulate during cold forming, which either leads to failure in the forming process or subsequently affects the performance. Structure-property relations are often investigated using numerical methods, e.g. crystal plasticity (CP) modeling with representative volume elements (RVE). In a previous study, CP-simulations on 3D-RVE were coupled with surrogate modeling techniques performing a variance-based sensitivity analysis. This analysis enables quantitative descriptions of the relationships between microstructure features with the damage tolerance, quantified by individual indicators for individual damage mechanisms. To investigate the effect of the material model and the corresponding phase properties, 500 sRVE simulations were carried out with different CPparameter sets and the damage tolerance is investigated. All sets stem from the same DP800 but were calibrated with different approaches. Surrogate models were trained on the simulative database to calculate Sobol Indices (SI), which are a measure of how strong damage tolerance is affected by a particular microstructure feature. The SI are compared for the individual material models and damage indicators. The structure-property quantification is heavily influenced by the different material models, resulting in different values for the SI and a different order for the individual microstructure features. The main factor for the pronounced differences is the differently evolving mechanical phase contrast between ferrite and martensite.

Abstract: Predicting the microstructural state during manufacturing is critical, as it directly governs the material's final mechanical properties. Accurate prediction of microstructure evolution in multi-stage industrial hot deformation processes, such as rolling, is limited by the lack of experimental data at intermediate stages, where direct measurement is impractical. To address this, an integrated methodology combining finite element (FE) simulation in QForm UK® software, physical simulation using the Thermo-Mechanical Treatment Simulator (TMTS), and artificial intelligence (AI) is proposed and investigated. The methodology is demonstrated for the 11-pass hot rolling of a 41Cr4 steel bar. Thermomechanical loading histories from an FE model of the industrial process were used to design and simulate a targeted TMTS experiment, generating a synthetic dataset via an analytical JMAK model that combines multiple recrystallisation mechanisms. This data was used to train a recurrent neural network (RNN) with an augmented physics-informed Long Short-Term Memory (LSTM) cell to predict the totally recrystallised fraction (RX) solely from loading history data. The AI model achieved high accuracy when validated within the TMTS simulation domain, successfully capturing different recrystallisation regimes. Implementation within commercial FE software enabled direct prediction in the rolling process simulation, yielding promising predictive capability, particularly in regions with thermal histories similar to the training data, highlighting the critical importance of training data diversity. This work establishes a proof of concept for a novel calibration methodology, where targeted physical simulation bridges the gap between industrial process complexity and data-driven AI model development, offering a practical solution for modelling scenarios where traditional experimental calibration is infeasible.