Abstract Hydroxyapatite (HA) is a bioactive ceramic widely applied in dental, bone replacement, and implant therapies because of its excellent biocompatibility and chemical similarity to natural bone. Despite these advantages, its poor strength, limited thermal stability, low crystallinity, and unfavorable surface morphology restrict its use in demanding, load-bearing implants. Improving these properties without compromising biocompatibility remains a key challenge in developing reliable biomedical materials. In this study, HA–titanium (Ti) composites were synthesized by the wet precipitation method and examined to understand how Ti content and processing temperature influence their structural and functional characteristics. Scanning electron microscopy (SEM) revealed distinct morphological changes: low Ti concentrations promoted finer, more uniform particles, whereas higher Ti content and elevated temperatures led to agglomeration, grain coarsening, and the appearance of rod-like TiO2 structures. X-ray diffraction (XRD) showed that crystalline HA was preserved at lower temperatures, with partial Ti addition into the HA lattice. At higher temperatures, reflections of rutile and anatase TiO2 phases emerged, indicating limited Ti solubility and the onset of phase segregation. Fourier-transform infrared (FTIR) spectroscopy confirmed these trends, with characteristic HA phosphate bands present across all samples, alongside band shifts, broadening, and diminished OH peaks that reflected lattice distortion. The growth of Ti– O bands at higher calcination temperatures further supported TiO2 formation. Collectively, these findings highlight that carefully controlled Ti incorporation enhances the crystallinity, thermal stability, and morphology of HA, while excessive Ti or high temperatures promote TiO2 segregation. Optimizing these parameters can pave the way for stronger, more reliable HA–Ti composites tailored for orthopedic, dental, and load-bearing implants that better serve patient needs.

Abstract The feasibility of laser surface melting (SLM) as a surface modification of WA-DED deposited AZ31 Magnesium alloy was experimentally investigated. Emphasis was placed on identifying the effects of independent critical LSM process parameters, such as laser power, scan speed, and hatch distance, and their corresponding laser energy densities on surface integrity, including roughness, wettability, microstructure, phase formation, microhardness, and electrochemical corrosion of WA-DED deposited AZ31 Mg alloy. The optimized LSM process parameters were a laser power of 50 W with a scan speed of 700 mm/min, and a hatch distance of 33 %, and a calculated laser energy density (LED) of 7.14 J.mm−2. The surface roughness of the WA-DED specimen increased to 5.5 μm after SLM at an LED of 7.14 JJmm−2; however, this poor surface roughness exhibited increased surface wettability. Moreover, at the same LED, the microstructure of the surface is refined to 4 μm, up to a depth of 297 μm from the surface, and HAGB dominates the grains, with an orientation towards the 0001 basal plane. Therefore, the surface hardness increased to 142 HV. The intermetallic phases of Al12Mg17 and Al8Mn5 were refined up to 50 nm with uniform distribution in the α-Mg matrix. The refined phases reduced the area ratio of the cathode (Al12Mg17) and anode (α-Mg), which slowed down the initiation of corrosion pits, resulting in increased corrosion resistance to 0.435 mm.y−1.

Abstract The effect of specimen shape on the fracture angle in tensile testing of copper alloy sheets was investigated. Specimens of which width over thickness are more than 30 were investigated and it was found that relatively thick and narrow copper alloy sheets exhibited a fracture angle oblique to the loading direction. In contrast, the fracture angle was perpendicular to the loading direction in the thinner and wider specimens. To understand the mechanism of the change in fracture direction, digital image correlation (DIC) analysis was performed. The DIC analysis showed that the oblique localizations of strain rate appeared in two directions in any thickness and width after diffuse necking. In thick specimens, one of the localizations was selected by the oblique fracture. In contrast, two localizations remained until the perpendicular fracture in thin and wide specimens. The analysis of the ratio of local strain rate revealed that the length strain over width strain was basically unchanged until fracture. However, in few cases, the length strain over width strain drastically changed just before the fracture. These results suggest that the remaining two localized strain rate and change in strain state lead the perpendicular fracture in thin and wide specimen. Regarding the edge of the specimen, the fracture angle tends to be oblique. This is presumably due to the less constrained condition of the edge, which is the possible reason for the oblique fracture of narrow specimen.

Abstract Platinum-barium (Pt-Ba) alloy cathodes are promising for magnetron amplifiers due to their high electron emission coefficient and excellent work function. High-temperature deformation characteristics have the utmost importance with respect to these types of metal alloy cathodes. Molecular dynamics (MD) simulations have been carried out to study tensile and creep deformation characteristics of a single crystal BaPt2 compound using a parameterized embedded-atom method (EAM) potential. The force-matching methodology and an optimization approach using converged density-functional theory (DFT) datasets have been used in this work to parameterize an EAM potential for the Pt-Ba alloy system. A list of fundamental properties, such as density, cohesive energy, and elastic properties, has been investigated via MD simulation, and these properties have been verified with the help of DFT analysis to examine the performance of the potential. Tensile deformation characteristics have been carried out at different temperatures from 300 K to 1600 K for strain rates of 108/s, 109/s, 1010/s, and 1011/s. Ductile characteristics have been found, as supported by Pugh's criterion. In addition, creep characteristics have been studied at different loads ranging from 100 MPa to 400 MPa for temperatures 0.3 Tm, 0.6 Tm, and 0.8 Tm (i.e., Tm is the melting temperature), where no tertiary region has been observed. Additionally, X-ray diffraction spectra and radial distribution characteristics have also been visualized through MD simulation.

Abstract Welding procedures in high-hardenability steels often lead to adverse microstructural changes, resulting in a sharp decline in mechanical properties within the weld metal zone and the heat-affected zone. Due to the limited tensile strength Rm of commercially available welding consumables, which in many cases do not exceed 1000 MPa, the reduction in mechanical properties can reach up to 60% in steels with hardness levels of 600 HBW. Martensitic boron steels are among the materials with the highest mechanical strength indices and are used both in components exposed to abrasive wear and in ballistic protection. Consequently, welding techniques often produce joint zones with functional properties (e.g., ballistic resistance or resistance to abrasive wear) that fail to meet the required performance of the base material. Only through advanced welding techniques, the use of high-quality fillers, and subsequent heat treatment can the highest mechanical strength indices be achieved in the weld zone. This article presents the results of tests on the resistance of 450 HBW grade steel welded joints to dynamic loads. The research demonstrated that, when subjected to firing using intermediate 7.62 × 39 mm ammunition (43 model, PS bullet) from a distance of 10 m, a minimum plate thickness of 5 mm ensures material continuity across all characteristic zones of the welded joint.

Abstract This study investigates the effects of post-rolling cooling methods (quench cooling, air cooling, and furnace cooling) on the microstructure and properties of Ti–Zr microalloyed steel via laboratory rolling tests. The microstructure is transformed from the lath martensite/bainite to the ferrite-dominated microstructure by decreasing the cooling rate and increasing the average grain size to 3.55 μm in furnace-cooled steel. Concurrently, transmission electron microscopy-based analysis reveals that the precipitate volume fraction increases from 0.038% to 0.106%, with the average size decreasing from 33.5 nm to 6.8 nm, enhancing the precipitation strengthening effect from 23 MPa to 121 MPa. Quench cooling forms a multiphase microstructure (martensite/bainite + ferrite), which reduces the yield ratio, while dislocation tangling in martensite decreases plasticity. Notably, quench-cooled steel exhibits high impact energy (151 J) despite low elongation. This is attributed to synergistic toughening by high dislocation density (1014 m−2) and retained austenite. Furnace-cooled steel balances strength (yield—716.5 MPa, tensile—787.6 MPa), elongation (18.9%), and 0 °C impact energy (133 J), thereby demonstrating cooling rate-controlled synergy between strengthening–toughening mechanisms in Ti–Zr microalloyed steel.

Abstract Wire arc additive manufacturing (WAAM), leveraging traditional gas metal arc welding (GMAW) technology, offers a promising approach for fabricating large-scale metallic components with high deposition rates. Among GMAW-based processes, cold metal transfer (CMT) and pulsed metal inert gas (MIG) techniques differ significantly in their metal transfer mechanisms and thermal inputs, which directly influence the resulting material properties. This study systematically compares the microstructural, mechanical, tribological, and corrosion characteristics of 316L stainless steel walls produced using CMT and pulsed MIG WAAM processes under similar heat input conditions (CMT: 323.48 J/mm, pulsed MIG: 329.14 J/mm). The CMT process produced finer grains (11.16 µm) compared to pulsed MIG (14.14 µm), contributing to slightly higher microhardness (171.90 HV versus 171.14 HV) and improved mechanical properties. Charpy impact toughness, yield strength, and ultimate tensile strength were all higher for the CMT process by 16.4%, 3.4%, and 1.3%, respectively, while pulsed MIG showed slightly higher elongation (56% versus 52.25%). Fractographic analysis revealed finer, more uniform dimples in the CMT samples, indicating ductile fracture behavior. In terms of tribological performance, the CMT process exhibited a lower coefficient of friction (0.216 versus 0.249) and a significantly reduced wear-rate (3.4 × 10−3 mm3/m versus 5.5 × 10−3 mm3/m). Corrosion resistance was also marginally better in the CMT samples, with a corrosion rate of 0.05235 mm/year compared to 0.05524 mm/year for pulsed MIG. Overall, the CMT process consistently outperformed pulsed MIG across multiple performance metrics, making it a more favorable choice for high-integrity additive manufacturing of stainless steel components.

Abstract Finite element (FE) micromechanical models have been extensively used to capture the overall mechanical properties of inhomogeneous materials using information from the microscale phase material. In general, there are three different categories of micromechanical models that use discrete microstructure: periodic model, windowing approach, and embedding technique. Each model has its own advantages and limitations. However, understanding the operating boundaries is critical for selecting the different micromechanical approaches. The objective of this article was to investigate various FE periodical micromechanical models and examine their distinct behaviors, with the aim of analyzing the underlying reasons for such variations. The deformation of dual-phase (DP) steel under uniaxial configuration was used in this research. A thorough comprehensive analysis was carried out to examine the difference between 2D and 3D models while incorporating various element types and geometries. Following from here, a detailed comparison contrasts modeled data with experimental findings across stress–strain curves, strain partitioning behavior, and strain distribution, examining model behavior against established definitions of uniaxial tensile stress conditions. The insights gained from this fundamental exploration are important to the advancement of the iterative methodology beyond the necking zone of tensile stress-flow curves. Results showed that the modeled principal stresses in existing 2D models utilizing plane stress and plane strain conditions fail to meet the criteria of a uniaxial tensile test stress state. Both the 3D micromechanical model and the 2D unit cell model with axisymmetric elements simulated stress states that were consistent with the condition of uniaxial tensile tests.

Abstract Understanding the behavior of carbon diffusion in austenite is critical to the design and optimization of heat treatment processes such as vacuum carburization of alloy steels. The carburization process is complex due to the intricate surface chemical reactions, resulting in a carbon content distribution curve that typically exhibits an inverse-S shape—a phenomenon that traditional carbon diffusion models fail to explain. Alternately, the carbon-level-dependent carbon diffusion model suggests that local carbon concentration impacts the carburization rate, implying that carburization parameters should be considered functions of carbon concentration. In this research, a forward analysis was first conducted by leveraging the analogy between the carburizing process and the heat transfer process to establish an efficient finite element modeling. A custom user subroutine, UMATHT, was developed, enabling the integration of the carbon-level-dependent diffusion model within abaqus-based analysis. Subsequently, an inverse analysis framework was formulated to facilitate the parametric identification of the carbon-level-dependent diffusion model. Combining the model prediction with a simulated annealing stochastic optimization algorithm, we identified the coefficients in the carbon diffusion model by minimizing the difference between experimental measurements and finite element simulations under various conditions within the parametric space. Our results have demonstrated that the carbon-level-dependent model not only offers smaller prediction errors in AISI 9310 steel but also accurately reproduces the characteristic inverse-S carbon distribution curve which traditional models cannot achieve. This research provides new insights into the vacuum carburization characterization of alloy steels.

Abstract Experimental and numerical investigations on the formability of longitudinally butt-welded tailor-welded blank of the same thickness prepared by friction stir welding are presented in this article. The friction stir-welding technique involves a solid-state stirring mechanism to butt weld the two blanks of aluminum alloy AA5083 and AA6082 both in the annealed state. To study the effect of welded region on formability, experiments are performed on tailor-welded blanks with and without the annealing operation. The tensile properties of the parent sheets, welded blanks, and welded region are determined by performing standard uniaxial tension tests. The elastic properties, true stress–true strain, and anisotropic data sets are used in the material model for the prediction of failure strains to develop forming limit plots. The predicted results from finite element analysis are validated with the experimental results obtained from the limiting dome height test. The annealing is observed to enhance the formability of the friction stir tailor-welded blank (FSTWB) by almost 13% in plane strain and equibiaxial stretch conditions.