Abstract Objectives To improve ductility and impact performance of AA2029–SS316L friction stir welded joints by optimizing key FSW process parameters using numerical simulation and statistical analysis. Methods Numerical simulations using ANSYS and Response Surface Methodology were employed, considering beam radius, clearance, force, and HAZ temperature, with ANOVA, fit statistics, and perturbation analysis validating structural responses. Results Optimized parameters – BWC 2.0067 mm, HAZT 1,600.41 °C, and force 5,482.06 kN – significantly enhanced ductility, reduced stress concentrations, and improved joint integrity under impact loading conditions. Conclusions The optimized FSW parameters exceed industry standards, demonstrating improved mechanical performance and structural reliability of AA2029–SS316L joints, confirming the effectiveness of simulation-driven optimization for advanced welding applications.

Abstract Hot compression experiments were conducted on GH2132 alloy rods using a Gleeble-3500 thermal simulator to investigate the high-temperature rheological behavior of the alloy at temperatures of 950, 1,000, 1,050, and 1,100 °C and strain rates of 0.001, 0.01, 0.1, and 1 s −1 . The results indicate that during hot deformation, the flow stress decreases with increasing temperature and increases with increasing strain rate. Based on the Arrhenius model and the Zener–Hollomon parameter, constitutive equations for the peak stress and strain-compensated flow behavior of GH2132 alloy were established. Based on the constructed hot processing map, the optimal hot working process window for GH2132 alloy was determined to be 1,025–1,100 °C/0.001–0.04 s −1 and 1,045–1,070 °C/0.69–1 s −1 .

Abstract The current study examines the inclined magnetic flow of nanoparticles with radiative flow and the Cattaneo-Christov dual diffusion model. The analysis involves the mixture of alumina Al 2 O 3 nanoparticles with (Carboxymethyl cellulose-water/ Al 2 O 3 ). In addition, this study examines how the arrangement and size of alumina nanoparticles affect the behaviour of nanofluid flow. The thermal Biot, solutal Biot, thermal source, and heat space dependent are also incorporated. The Cattaneo-Christov heat and mass flux formulas are used to make a gradual change to the heat and concentration equations. The current issue is represented using partial differential equations (PDEs), which are then transformed into ordinary differential equations by appropriate similarity transformations. The acquired highly nonlinear system of modeled equations has been solved by consuming the numerical approach through the boundary value problem Bvp4c method. The primary objective of this research is to examine the characteristics of velocity, temperature, and concentration in a nanofluid, specifically focusing on the impact of the size and spacing of aluminum nanoparticles. In addition, the calculation of heat and mass transfer is performed for the Cattaneo-Cristove dual diffusion. Velocity distribution has been depreciated for the enhancing values of magnetic field and porosity for interspacing and radius of nanoparticles. Moreover, drag friction is lower due to the larger values of the magnetic field and porosity variable.

Abstract Nb microalloying is of significance to the grain refinement and mechanical properties of DP steels. In the present study, two DP steels without/with addition of Nb were produced by the TMCP process and the effect of Nb on the microstructure and mechanical properties was comparatively investigated by characterization methods of optical microscopy (OM), electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results show that the addition of 0.02 wt% Nb in the DP steels, the volume fraction of martensite increases from 43 to 85.2 vol%, and the equiaxed grain and elongated grains are obtained with grain size decreasing from 1.88 to 1.66 μm during the hot rolling process. Furthermore, during the tempering, the martensite lath of the DP steel with Nb grows slower (from 127.4 to 139.3 nm). The DP steel with addition of Nb exhibits a better combination of strength (∼1,281 MPa tensile strength) and ductility (∼16.0 % total elongation), attributed to grain boundary strengthening, dislocation strengthening and solid solution strengthening.

Abstract This study analyses the entropy and heat transfer characteristics of couple-stress Casson fluid in a porous vertical microchannel, incorporating the effects of isothermal cubic autocatalytic chemical reactions, variable thermal conductivity, uniform heat source/sink, and thermal radiation. The governing equations are transformed into dimensionless form and solved numerically using the fourth and fifth-order Runge-Kutta-Fehlberg method. Key findings reveal that the inverse couple-stress parameter and variable thermal conductivity, significantly influence temperature distribution and fluid flow, enhancing heat transfer efficiency throughout the microchannel system. The study also highlights that homogeneous-heterogeneous reactions reduce concentration levels, improving lubrication and optimizing thermal performance. Additionally, entropy generation increases with higher Biot number, variable thermal conductivity, radiation, and heat source/sink effects. The Nusselt number decreases with increasing thermal conductivity, while drag force minimizes as the inverse couple-stress parameter rises. These findings contribute to the optimization of microfluidic thermal systems, with practical applications in energy-efficient cooling technologies, microchannel heat exchangers, advanced chemical reactors, and biomedical engineering, where precise heat and mass transfer control is essential for improved performance and efficiency.

Abstract In view of the fact that the current experimental method is not very satisfactory to study the solid solution behavior of rare earth elements (RE) in steel, it is an effective and economical method to replace the experimental research with the simulation calculation method. In this article, the Fe-RE (La, Ce, Y) systems were constructed based on the density functional theory, and mechanical properties of doping systems were calculated. The calculation results of the solvation energy show that La, Ce, and Y can form stable solid solutions in α-Fe, and Ce has the highest solid solubility in α-Fe, followed by Y and La. The results of elastic moduli show that the doping of RE (La, Ce, Y) reduces the incompressibility, shear strain resistance, stiffness, and Vickers hardness of the doping system, while increasing the toughness and machinability. The strength properties of the doping systems are Fe–Ce > Fe–La > Fe–Y, and the toughness and machinability are opposite. In Fe–RE (La, Ce, Y) doping systems, RE (La, Ce, Y) reduce the metal bond strength of the Fe system, which is the fundamental reason for the decrease of the strength properties of the doping system. In addition, in doping system, Fe atoms gain electrons and RE (La, Ce, Y) atoms lose electrons. And the increase of electron cloud density in the doping system can be used to explain the improvement of toughness and machinability of the system.

Abstract Submerged arc welding method was used to weld 40 mm thickness Q690qE high-strength steel to study the influence of welding heat input on the microstructure and properties of Q690qE joints. The result shows that welded seam with full penetration and no obvious defects is achieved in the Q690qE joints when the welding heat input ranges from 22.5 to 33.6 kJ·cm −1 . The microstructure of welded seam mainly consists of acicular ferrite and granular bainite (GB), the microstructure in coarse-grain zone is GB and lath martensite. As the welding heat input increases, the microstructure of coarse-grain zone becomes lath bainite (LB) and a small amount of GB and the microhardness decreases. The microstructure of the fine-grained area mainly includes ferrite, GB, and a small quantity of LB. In terms of impact toughness, with the heat input increasing, the impact toughness at the center of welded seam and the heat-affected zone decreases subsequently. The tensile test results of the welded joints show that the fracture always occurs in the parent material area, with a tensile strength higher than 864 MPa, and the elongation after fracture decreases as the heat input increases.

Abstract Biopolymer-modified cementitious repair material (CXT) is a composite material designed to enhance the properties of traditional cementitious materials through the incorporation of biopolymers. CXT is formed by blending cement (C) with biopolymers such as xanthan gum (XG) and additives like tartaric acid (TA), which improve the material’s performance characteristics. This study investigates the effects of varying dosages of XG, TA contents, and curing durations on the performance characteristics of CXT. We evaluated key performance indicators, including the flowability, workability, setting time, compressive strength, and shrinkage. The optimal formulation XG 1:2 TA0.6 achieved a maximum compressive strength of 25 N·mm−² and a flexural strength of 9.4 N·mm−², with negligible shrinkage. The results showed rapid early strength development, with the material reaching over 77% of its final compressive strength within the first 14 days. These findings highlight the potential of CXT for crack-repair applications, offering improved workability, accelerated setting times, and reduced environmental impact compared to traditional repair materials. This study provides valuable insights for optimizing the formulation of CXT for enhanced performance in real-world applications.

Abstract To investigate the diffusion of sulfate ions in coral seawater concrete under the mechanism of the wetting–drying cycle of sulfate solution, the concentration of sulfate ions in coral concrete at different depths under different cycling cycles was tested in this experiment. Finite-element numerical simulations were then carried out using COMSOL software. The results showed that the sulfate ion concentration in the concrete at the same depth increased steadily with time, and the erosion depth also increased. The numerical simulations successfully reproduced the diffusion of sulfate ions in coral seawater concrete under the mechanism of the wetting–drying cycle of sulfate solutions.

Abstract Different combinations of normalizing and tempering were carried out to optimize the microstructure and enhance the high-temperature mechanical properties of HRB400FR fire-resistant steel bars. The results showed that with the increasing of the tempering temperature from 400 to 600°C, the steel bar’s hardness decreases linearly, mainly due to the formation of quasi-polygon ferrite and granular bainite. Besides, the reduced width and the dissolution of the lath bainite also undermine the performance of the tempered steel bars. The highest Vickers hardness of 380 HV is achieved when the steel is normalized at 950°C and then tempered at 400°C, mainly due to precipitation strengthening and bainite strengthening. The hardness of the test steel tempered at 600°C gives the lowest value, only 230 HV since the least amount of bainite is obtained. When the tempering temperature reaches 650°C, the hardness rises to 260 HV due to the formation of the lath bainite. The emergence of needle bainite generally reduces the matrix grain size, and the appearance of lath martensite refines the precipitated carbides.