Singh, Jaiveer

The current study focuses on investigating the effect of in-plane cyclic shear (IPCS) on the microstructure and texture evolution in an AZX311 Mg alloy sheet using a customized in-plane shear jig. Samples were deformed at two distinct strain levels of 0.05 and 0.10, with tests conducted over different numbers of deformation cycles at each strain level. A detailed microstructural investigation using electron backscatter diffraction (EBSD) revealed that in-plane cyclic shear induced the formation of numerous tensile twins (TTWs) in the alloy sheet. Both the shear strain and the number of deformation cycles contributed to an increase in the twin volume fraction (TVF), which played a critical role in texture evolution. Notably, unlike in-plane shear (IPS) deformation, where two satellite peaks appear in opposite quadrants, in-plane cyclic shear resulted in satellite peaks across all four quadrants of the pole figure. The evolution of texture components across all four quadrants arises from the load variations under forward and reverse loading during cyclic deformation. Thus, in-plane cyclic shear deformation can generate texture components along nearly all directions in the pole figures. Additionally, microstructural and microtextural analyses revealed that TTW is the dominant deformation mechanism, contributing to texture evolution. Furthermore, the resolved shear stress (RSS) analysis indicated that prismatic slip activity predominantly governs dislocation slip behavior. © 2025

This study aims to investigate the mechanical behaviors of Ti–15 V–3Cr–3Al–3Sn (Ti-15333), a metastable β titanium alloy. Thermomechanical processing of the alloy sheet in its as-received state included solution treatment at 800°C, followed by varying aging temperatures from 450°C to 700°C. As the aging temperature rises, α precipitation increases with a fine, uniform distribution attained at 500°C to 550°C. Increased aging temperature and time causes precipitation not only at grain boundaries but also intra-granularly with morphology change from globular to lath. However, if the temperature goes above 600°C, the α phase starts to coarsen. Aged samples showed an upward trend in tensile strength that peaked and then declined, while % elongation showed an inverse trend, with optimal properties observed after 6 h aging at 500°C and 550°C. This is consistent with the idea that mechanical properties evolve alongside microstructure. The examination of the local fracture surface of aged tensile specimens using EBSD revealed a random texture. KAM value reflecting dislocation density rose with both aging temperature and duration, with its highest average reported for 6 h aging condition at 500°C and 550°C, aligning with peak level of α precipitation. The size, shape, and size distributions of α precipitates also had a pronounced impact on the fracture modes observed in the specimens. The likelihood of cleavage-like fractures occurring was higher in the under and peak-aged specimens when compared to the over-aged counterparts at 600°C and beyond. This tendency suggests that the over-aged specimens, featuring coarse α platelets, should exhibit decreased resistance to deformation and higher ductility, which is indeed the case. Investigation and analysis of different microstructures and mechanical properties obtained under different aging conditions can aid in summarizing the principles under laying deformation and fracture mechanisms of metastable β titanium alloy, potentially enhancing the service life of components and providing a foundation for alloy fabrication with customized microstructure.

In this study, the effects of pre-strain-induced tensile twins (TTWs) and controlled heat treatment on the formability behavior of AZX311 Mg alloy sheets were investigated. A 4% compressive strain was applied to pre-strain the sheets using the in-plane compression (IPC) technique along the rolling direction (RD) to introduce TTWs. The pre-strained (PS) samples were subsequently heat-treated at 250 °C, 350 °C, and 400 °C independently for 1 hr, and are termed as PSA1, PSA2, and PSA3, respectively. Erichsen cupping tests were conducted to assess the formability of the sheet samples under different initial conditions. The results showed that the PS sample heat-treated at 250 °C for 1hr exhibited a decrease in the Erichsen index (IE) compared to the as-rolled sample, whereas PSA2 and PSA3 samples showed an increase in IE values. Microtexture analysis revealed that most of the TTWs generated through pre-twinning were stable at 250 °C; however, the twin volume fraction reduced to 41% at 350 °C compared to the PS samples due to enhanced thermal activity at that temperature. Furthermore, PSA2 samples showed severe grain coarsening in some areas of the sample, and the fraction of such grains increased in the PSA3 samples. The stretch formability (IE value) of PSA2 samples showed a 32.3% increase compared to the as-rolled specimens. Additionally, the analysis of the deformed specimen at failure under the Erichsen test indicated that considerable detwinning occurs in the PS and PSA1 samples, whereas dislocation slip activity dominates in the PSA2 and PSA3 samples during stretch forming. Apart from detwinning and dislocation slip, deformation twins were also observed in all samples after the Erichsen test. Thus, this work highlights the importance of texture control and its underlying mechanisms via pre-twinning followed by heat treatment and their impact on the room temperature (RT) stretch formability of AZX311 Mg alloy sheets.

In this study, a novel Ni46.8Fe23Co10V7(Al, Si)6.6 compositionally complex alloy (Ni-CCA) has been designed by merging the CALPHAD approach with the theoretical concepts (enthalpy of mixing, atomic radius mismatch parameter, valence electron concentration (VEC), and pair sigma forming elements (PSFE)). The theoretical analysis and the CALPHAD modeling predict the formation of a single FCC phase at room temperature along with the absence of TCP phases in the designed Ni-CCA. Subsequently, the pseudo-binary phase diagram obtained from Thermo-Calc through the latest HEA database predicts the presence of newer strengthening ordered phases containing Ni-Al-Si at elevated temperatures in Ni-CCA. Microstructural characterization of as-cast Ni-CCA displayed the formation of γ-FCC phase dominated microstructure containing a minor fraction of BCC phase at room temperature whereas high-temperature compression depicted synergistic precipitation of Ni-Al-Si containing L12 type precipitate and dynamic recovery/recrystallization events during deformation leading to a marginal drop in yield strength (YS) at 800 °C. Moreover, the formation of necklace microstructure in a deformed specimen confirms the occurrence of dynamic recrystallization (DRX) in novel Ni-CCA.

The microstructure development and mechanical behaviour of dissimilar metal welds between ferritic and austenitic steel, as well as their application in nuclear power plants, are discussed in this review paper. Nuclear reactor components, such as steam generators and pressure vessels, consist primarily of SA508 due to their low cost and high operating temperatures and pressures. The welding of dissimilar metals is crucial due to variations in physical characteristics such as thermal conductivity, thermal expansion coefficient, mechanical properties and chemical compositions. The principal challenges of dissimilar ferritic and austenitic steel welding are the subject of this review work. Weldability issues include a sharp change in mechanical and metallurgical characterization across the fusion line, carbon migration, cyclic thermal stresses and residual stresses, which necessitate a thorough investigation of the welded joint. Generally, austenitic steel and nickel-based fillers are used to join austenitic and ferritic steel materials; however, owing to many weldability concerns, nickel-based consumables are replacing austenitic consumables. Another critical issue in the weld joint is the selection of appropriate welding consumables, and detailed explanations of the benefits of employing a buttering layer on the ferritic side are provided. The effect of heat treatment on the metallurgical and mechanical characteristics of the weld joint, as well as the formation of residual stress, has also been thoroughly explored.

The objective of this study is to develop and examine coating fluxes for SMAW electrodes intended for use in nuclear power plant steel welding. A set of 21 unique flux compositions is created using the extreme vertices design methodology. These compositions predominantly consist of SrO-CaO-Al2O3-CaF2 fluxes. At a temperature of 1373 K, an in-depth investigation is carried out to assess key properties, including the work of adhesion, spread area, contact angle and floatation coefficient. Additionally, the surface tension of these flux compositions is estimated. XRD and FTIR analysis methodologies have been employed for the purpose of examining and identifying the phases that exist within both the flux and slag. Furthermore, structural analysis of the molten material is conducted through the examination of quenched slag powder. Results reveal that the individual components CaO, CaF2 and binary interaction of Al2O3 × SrO have a significant effect on the contact angle and floatation coefficient. Individual interactions of CaO, SrO, Al2O3 and CaF2 exert a positive impact on the spread area. The individual components Al2O3 and SrO were found to have a significant effect on the work of adhesion.

The current study examined the deformation mechanisms, microstructure, and texture evolution in AZX311 Mg alloy sheets subjected to in-plane shear (IPS) deformation. Different levels of shear strains, with values 0.05, 0.10, and 0.15, were applied along the rolling direction (RD) using a specialized in-plane shear testing jig. The strain measurement for the applied shear deformation was conducted utilizing the digital image correlation (DIC) technique. The strain distribution was found to be nearly homogeneous over sufficiently large areas, thereby allowing the microstructural measurements to yield relevant statistical data. A thorough microstructural examination across the thickness using electron back-scattered diffraction (EBSD) revealed that the application of IPS strain led to the formation of a significant number of tensile twins (TTWs) in the sheet. This was evidenced by the emergence of two satellite peaks at the periphery of the pole figures. As the shear strain increased, the proportion of TTWs in the material also increased, encompassing the entire parent grain and leading to the formation of what has been termed as “all-twinned microstructure”. The microstructural and texture investigation after IPS deformation revealed that TTWs were the dominant deformation mechanism that defined the microstructure and texture under IPS deformation, while dislocation slip activity was dominated by prismatic slip, as evidenced by the resolved shear stress analysis in this study. Consequently, this research highlights the effect of IPS deformation on the microstructure and texture evolution throughout the thickness of an Mg alloy sheet and elucidates the underlying mechanisms.

This study investigates electrode coatings designed for use in nuclear power plant weld joints, particularly their electrical, thermophysical and physicochemical properties. The Al2O3-CaF2-CaO-SrO-based shielded metal arc welding electrodes were developed using the extreme vertices design technique. The coating composition's structure and phases were analyzed using X-ray diffraction, while Fourier transform infrared spectroscopy analysis was used to identify the types of bonds present. Advanced characterization methods were utilized to assess the coating formulations’ physicochemical, thermophysical and structural aspects. Thermal properties, including specific heat, thermal diffusivity and conductivity, were evaluated using a hot disk apparatus, while thermogravimetric analysis was employed to determine the enthalpy change and thermal stability of the flux coating. The electrical properties of the flux coatings were examined using a precision LCR instrument. Statistical analysis was employed to create regression models for each coating property to investigate the influence of mineral constituents on the flux coating properties. Regression analysis is a statistical method used to establish a relationship between mineral interactions. In flux composition selection, it can help determine the physical significance of each factor and its relationship with the coating's performance. The results indicate that the mineral constituents’ individual elements, binary and tertiary interactions, significantly impact the flux composition's physicochemical, electrical and thermophysical properties. © IMechE 2023.

The performance of polyether-ether-ketone (PEEK) as an orthopedic biomaterial can be improved by bulk modification of PEEK through hydroxyapatite (HA) incorporation. In this context, we have studied the size effect of HA particles (from micro to nano) on the high-temperature extrusion, physicochemical and biological properties of the extruded PEEK-HA filaments. Our study showed that incorporation of HA into PEEK up to 5% w/w allows filament formation through single screw extrusion. However, a more significant temperature gradient between the hopper end and nozzle was necessary for the extrusion of nano-HA incorporated PEEK compared to micro-HA incorporated PEEK. The micro-CT revealed a homogeneous dispersion of HA particles within the extruded filaments. The inclusion of nano HA powder (<200 nm) in PEEK (5%w/w) did not alter the mechanical properties of PEEK. When checked in vitro using MG-63 cells, PnHA exhibited better cytocompatibility, as evidenced by calcein-AM staining and MTT assay. Cellular expression of vascular endothelial growth factor and alkaline phosphatase was also found to be 2–3 fold higher for PnHA. Further, PnHA was found to be a promoter of angiogenesis when checked by tube formation assay. The results together implied that nano-HA is more suitable than micro-HA for improving the essential qualities of PEEK for orthopedic applications. Highlights: Incorporation of HA in PEEK improves the performance of PEEK as a biomaterial. PEEK with 5% micro/nano HA can be extruded as PEEK-HA composite filament. Variation in HA particle size (micro/nano) impacts the performance of composite. PEEK-HA composite filament has improved angiogenic and osteoconductive properties. © 2024 Society of Plastics Engineers.

The evolution of microstructure and texture in Mg-3Al-1Zn-1Ca alloy sheets subjected to in-plane shear (IPS) loading was investigated using experimental techniques and viscoplastic self-consistent (VPSC) modeling. The specimens were deformed under varying degrees of IPS strain (γ₁₂ = 0.05, 0.10, and 0.15) using a customized jig. Electron backscatter diffraction (EBSD) observations revealed profuse tensile twinning (TTW) even at an IPS strain of 0.05, with its intensity continuously increased as the IPS strain increased. The TTWs progressively engulfed parent grains with increasing shear strain, evolving into an unusual deformation twin morphology. Furthermore, VPSC model predictions confirmed basal slip as the dominant deformation mode at low IPS strains, transitioning to prismatic slip dominance at higher IPS strains. The activity of the TTW mode was significantly higher during the initial stages of IPS strain and saturated to lower values at higher strains. VPSC simulation results also indicated preferential shear accumulation on a single twin system, explaining the phenomenon of a single twin variant engulfing a parent grain. Additionally, the influence of individual slip and twin modes on texture evolution was evaluated through orientation tracking of representative grains at various shear strain increments using VPSC simulation. The simulation results quantitatively highlighted the activities of basal slip, prismatic slip, and tensile twinning, establishing a correlation between texture evolution and the underlying deformation mechanisms. © 2025