Half-metallic ferromagnets, conducting for one spin channel while insulating for the other, are highly desirable for spintronic applications due to 100 % spin polarization around the Fermi level. Cobalt-based half-metallic Heusler compounds have attracted enormous attention due to their large spin polarization and a high magnetic transition temperature. In the present study, we report the experimental and theoretical investigation of crystal structure and anomalous Hall effect (AHE) in half-metallic ferromagnet Co2VAl. The structural investigation of high-resolution synchrotron x-ray diffraction data reveals 10 % antisite disorder between V and Al atoms within the L21 ordered crystal structure. The scaling analysis of anomalous Hall data shows that the AHE in our system is mainly driven by the Berry curvature in the momentum space. The magnitude of experimental intrinsic anomalous Hall conductivity (AHC) due to the momentum space Berry curvature is about 44.67 +/- 0.02 S/cm at 5 K, which is less than the theoretically calculated AHC for the ordered structure. Our theoretical calculations suggest that the lower AHC obtained for the present system is due to the reduced Berry curvature in the disordered case with negligible impact on half-metallicity of the system.

Purpose Wire-arc-based additive manufacturing (WAAM) is a promising technology for the efficient and economical fabrication of medium-large components. However, the anisotropic behavior of the multilayered WAAM-fabricated components remains a challenging problem. Design/methodology/approach The purpose of this paper is to conduct a comprehensive study of the grain morphology, crystallographic orientation and texture in three regions of the WAAM printed component. Furthermore, the interdependence of the grain morphology in different regions of the fabricated component with their mechanical and tribological properties was established. Findings The electron back-scattered diffraction analysis of the top and bottom regions revealed fine recrystallized grains, whereas the middle regions acquired columnar grains with an average size of approximately 8.980 µm. The analysis revealed a higher misorientation angle and an intense crystallographic texture in the upper and lower regions. The investigations found a higher microhardness value of 168.93 ± 1.71 HV with superior wear resistance in the bottom region. The quantitative evaluation of the residual stress detected higher compressive stress in the upper regions. Evidence for comparable ultimate tensile strength and greater elongation (%) compared to its wrought counterpart has been observed. Originality/value The study found a good correlation between the grain morphology in different regions of the WAAM-fabricated component and their mechanical and wear properties. The Hall–Petch relationship also established good agreement between the grain morphology and tensile test results. Improved ductility compared to its wrought counterpart was observed. The anisotropy exists with improved mechanical properties along the longitudinal direction. Moreover, cylindrical components have superior tribological properties compared with cuboidal components.

Wire plus arc additive manufacturing (WAAM) is rapidly growing into a popular and cost-effective technology for manufacturing medium-large complex structured components. WAAM is a novel metal additive manufacturing method that deposits material layer by layer using an electric arc as a heat source, allowing the creation of metal components with high mechanical characteristics. The procedure allows for the construction of a near-net-shape structure at a rapid pace of production (50–130 gm/min) and material utilization efficiency (80–90 %). The present study mainly focuses on the fabrication of the WAAM structure and a detailed investigation of the mechanical and corrosion performance of multi-layer fabricated wall components. The most versatile and widely applicable stainless steel SS316L material is employed to build multi-layered wall structures. The average micro-hardness of the WAAM-built structure along the building direction was found to be 197.43±1.46 HV0.3 and that of the commercially available counterpart was found to be 187.26±1.17 HV0.3. Moreover, the maximum hardness was observed close to the bottom region (201.86±1.44 HV0.3) which further reduces with the building height. The ultimate tensile strength, and yield strength of the WAAM printed wall obtained as 573.81±2.3 MPa, and 275.41±1.1 MPa respectively found to have improved mechanical strength to that of wrought counter-part however the ductility in the form of percent elongation gets slightly reduced. Furthermore, comparable corrosion resistance was observed for the WAAM fabricated wall structure and conventionally manufactured SS316L structure. The bottom region experiences better corrosion resistance compared to the upper region in both saline environment and acidic corrosion solution with an average corrosion rate of 0.0276 mm/yr, and 0.0366 mm/yr respectively.

The study investigates the feasibility of emerging wire arc additive manufacturing technology to fabricate steel structures. The grain morphology and phase transformation of the WAAM-printed structure have been thor-oughly examined and investigated their influence on the mechanical, tribological, and corrosion performance. The structure is characterized by fine equiaxed grains nearer to the cold substrate and coarse columnar grains along the upper regions. The average grain size in the top, middle, and bottom regions of the printed wall is 12.34 +/- 5.81 mu m, 10.27 +/- 2.84 mu m, and 4.33 +/- 0.89 mu m respectively. The higher temperature gradient in the bottom regions led to the ferrite-austenite solidification mode that switched toward the primary austenite so-lidification mode in the upper layers. The printed parts witness superior mechanical properties with an improved micro-hardness and tensile strength however reduced ductility compared to the conventionally produced steel. The longitudinal direction of the printed parts experienced slightly higher hardness than the transverse. The tribological performance in different regions is investigated under different loading conditions and discovered an improvement in the wear-resistant properties of the fabricated part to its wrought counterpart even at high load conditions. Moreover, comparative corrosion resistance properties of the WAAM and wrought steel were detected with a slightly higher corrosion rate along the upper region in a moderately saline environment with flowing and stagnant conditions. The study detects the dependence of the characteristics properties on the grain morphology and existing phases in different regions of the arc additive-manufactured steel wall.

The manipulation of the anomalous Hall effect (AHE) by controlling magnetization is of great interest in condensed matter physics due to its potential application for the practical design of spintronic devices. In this study, we report a combined experimental and theoretical investigation of the AHE in the MnSb manganese pnictide. Temperature-dependent magnetization measurement indicates spin reorientation transition (SRT) temperature at similar to 120 K (TSR). Magnetotransport data shows that negative magnetoresistance increases from room temperature up to SRT temperature 120 K, then decreases and becomes positive at very low temperatures. The anomalous Hall conductivity (AHC) shows temperature-independent behavior from room temperature to TSR followed by a drop and sign reversal at low temperatures. Detailed scaling analysis of anomalous Hall data suggests that the AHE above TSR is primarily governed by the intrinsic Berry curvature and the obtained value of intrinsic AHC is about 310 S/cm. In contrast, below TSR, the extrinsic skew scattering becomes the dominant contributor to the AHE compared to the intrinsic Berry curvature and the obtained value of intrinsic AHC is about-28 S/cm. The first-principles calculations reveal that changes in the sign and magnitude of the intrinsic AHC are attributed to modifications in the Berry curvature when the magnetic moment undergoes rotation from the c-axis to the ab-plane. Our study yields a compound exhibiting large AHC and offers an insightful comprehension of the anisotropic behavior of AHE due to the modification of Berry curvature.

Wire arc additive manufacturing is the derivative of the metal AM process based on arc welding and a preferred technology for manufacturing large metallic components with medium to low complexity. The major problem with the WAAM process arises due to severe heat accumulation within the built structure and repeated heating-cooling cycles during layer-by-layer material deposition. Therefore, the interlayer time interval influences the microstructure and mechanical properties of the components. This paper has characterized the impact of interlayer cooling time on the microstructure and mechanical properties of SS-316L build. The local thermal cycle causes a non-uniform cooling rate, which alters the structure of the grains. The grain size decreases with increased interlayer time interval due to a faster cooling rate brought on by the low inter-pass temperature. A wider and smaller wall was deposited with less time interval. X-ray diffraction analysis confirms the formation of austenite and ferrite phases in all WAAM components with a slight difference in intensity. The wall constructed with a maximum time interval has a maximum value of average Vickers micro-hardness 244.00 HV0.5 and possesses the least coefficient of friction due to its improved property by the formation of fine grains. The maximum volume of materials was worn out from the wall deposited with lesser cooling time. The designed numerical model predicts the peak temperature and heat accumulation within the built structure which further relates to the morphological and mechanical properties of printed parts.

Topologically protected nontrivial spin structures attract significant interest in condensed matter physics for their utilization in low‐power‐consumption spintronics devices, memory devices, etc. The topological Hall effect (THE) is an additional Hall resistivity in the system arising from real‐space Berry curvature picked up by conduction electron passing through the nontrivial spin texture. Compared to expensive neutron diffraction measurements, THE is often used as a cost‐effective tool to investigate nontrivial spin texture in the materials. In the present manuscript, THE in the (Mn1−xFex)3.25Ge (x = 0.4) alloy is studied using magneto‐transport measurements. Maximum THE is found in the system about 0.65 μΩ cm at 150 K, which is in contrast to the pristine Mn3Ge that has zero THE. The strong temperature variation of THE suggests that the noncoplanar spin structure due to competition among the magneto‐crystalline anisotropy, antiferromagnetic coupling, and ferromagnetic exchange interaction is the main source of THE in the present system. Herein, it is shown that chemical doping can be an effective way to induce THE in the material with vanishing THE in its parent phase.

Skyrmions are localized swirling noncoplanar spin textures offering a promising revolution in future spintronic applications. These topologically nontrivial spin textures lead to an additional contribution to the Hall effect, called the topological Hall effect. Here, we investigate the origin of the topological Hall effect-a trademark of skyrmions-in a centrosymmetric shape memory Heusler alloy (SMHA) Mn2NiGa. The magnetization measurement unveils the presence of austenite to martensite transition in the studied system. The topological Hall effect (THE) in the present system is examined experimentally and theoretically. The presence of a large THE in the austenite (cubic) phase of the system strongly suggests that the observed THE in Mn2NiGa cannot be attributed to the antiskyrmions stabilized by D2d symmetry as reported earlier. To comprehend the underlying mechanism behind the origin of THE, we have performed micromagnetic simulations for a range of magnetic field with a small value of DMI (local DMI) to consider the possible impact of earlier reported atomic disorder in the centrosymmetric SMHA Mn2NiGa. The results showed the stabilization of Neel-type skyrmions, which can be assigned to the expected local symmetry breaking at the interface of disorder originated ferromagnetic nanoclusters and ferrimagnetic lattice of the system. A theoretical calculation of topological Hall resistivity by utilizing micromagnetic simulations is performed, which is of the same order as the experimentally obtained values in the both martensite and austenite phases.

Powder mixed Electrical Discharge machining (PMEDM) is an effective process in improving rate of material removal (MRR) and surface finish. But influence of powder mixed in the dielectric on the surface quality of the machined profile is an essential aspect of machining effectiveness. Nimonic 263 though imbibed with many advanced properties, is regarded as a difficult to machine materials by conventional methods. Spark erosion machining process is independent of the workpiece hardness and can machine any electrically conductive material. Hence EDM can be an effective alternative for machining Nimonic 263. But machining performance may vary depending upon the working medium. In this work, performance of spark erosion process in machining of Nimonic 263 has been evaluated using three different dielectric conditions. Kerosene has been taken as the dielectric fluid. Graphite micro powder as a conductive powder and alumina micro powder as a non-conductive powder have been added to the dielectric fluids for assaying their influence on the responses. Only the dielectric condition has been varied and all other parameters viz. pulse on time, peak current, gap voltage, duty factor and spark time have been kept constant at 20 mu s, 6 A, 30 V, 42% and 3 s respectively. Dielectric breakdown voltage (DBV), surface topography, surface crack density (SCD), recast-layer thickness (RLT), microhardness have been considered as the performance measures in this study. Apart from these responses, 3D surface analysis has been carried out for the machined surfaces obtained by each of the dielectric conditions. Graphite powder mixed kerosene has been found to be the most suitable dielectric condition with best surface finish. Copyright (C) 2022 Elsevier Ltd. All rights reserved.

The anomalous transport properties of Heusler compounds become a hotspot of research in recent years due to their unique band structure and possible application in spintronics. In this paper, we report the anomalous Hall effect in polycrystalline NiCoMnGa quaternary Heusler compound by experimental means and theoretical calculations. The experimental anomalous Hall conductivity (AHC) was found at about 256 S/cm at 10K with an intrinsic contribution of 121 S/cm. The analysis of Hall data reveals the presence of both extrinsic and intrinsic contributions in AHE. Our theoretical calculations show that a pair of spin-orbit coupled band formed by the band splitting due to spin-orbit interaction (SOI) at the Fermi level produces a finite Berry flux in the system that provides the intrinsic AHC about 100 S/cm, which is in good agreement with the experiment.

Wire arc additive manufacturing (WAAM) is one of the emerging AM processes used to fabricate medium to large size components based on the principle of direct energy deposition (DED). Despite having several benefits of the WAAM process, few limitations such as parts distortion and induced residual stress have been a cause of concern in this area. Therefore, the work focuses on finite element process simulation and modeling of thermal cycle prevailed during the fabrication of multi-layered stainless steel (SS316L) wall using WAAM. The model is developed using the COMSOL Multiphysics® software. The simulation results predict the thermal history of the wall fabricated at the selected process parameters. Thus, the model helps in controlling the thermal gradient and the residual stress induced due to non-uniform cooling cycle developed during the manufacturing process. The effective study and altering the process input parameters cutoff a large number of trial experiments and save the production time and associated material loss.

Wire arc additive manufacturing (WAAM) is popularly becoming an important and cost-effective manufacturing process to fabricate medium-large size components. The process provides the ability to build a near-net-shape structure with a high production rate (50-130 gm/min) and high material usage efficiency (80-90%). However, as per other additive manufacturing (AM) processes, process planning and optimization provide a uniform, time-efficient, and defect-free deposition. Therefore, this study focuses on the parametric study and process optimization to fabricate multi-layers wall components. The most commonly and widely used SS304 stainless steel metallic wire has been used to fabricate four-layered wall structures using multi-layer bead deposition. Open circuit voltage (OCV); wire feed speed (WFR) and shielding gas flow rate (SGFR) has been selected as the input process parameters and the bead height to width ratio (H/W) selected as the output parameter. The nine experiments were performed using the L9 orthogonal array based on the Taguchi method and then implemented the analysis of variance (ANOVA) to describe various properties. The resultant data has been analyzed and studied using Minitab-17 software. The results obtained showed that the optimum condition for the H/W ratio is 24 V OCV, 14 m/min WFR, and 10Lit/min SGFR. The order of process parameters influencing the H/W ratio is OCV, WFR, and SGFR. These results were validated by conducting confirmation experiments and found satisfactory. Copyright (C) 2022 Elsevier Ltd. All rights reserved.

Spin gapless semiconductors exhibit a finite band gap for one spin channel and closed gap for other spin channel, emerged as a new state of magnetic materials with a great potential for spintronic applications. The first experimental evidence for the spin gapless semiconducting behavior was observed in an inverse Heusler compound Mn2CoAl. Here, we report a detailed investigation of the crystal structure and anomalous Hall effect in the Mn2CoAl using experimental and theoretical studies. The analysis of the high-resolution synchrotron x-ray diffraction data shows anti-site disorder between Mn and Al atoms within the inverse Heusler structure. The temperature-dependent resistivity shows semiconducting behavior and follows Mooijs criteria for disordered metal. Scaling behavior of the anomalous Hall resistivity suggests that the anomalous Hall effect in the Mn2CoAl is primarily governed by intrinsic mechanism due to the Berry curvature in momentum space. The experimental intrinsic anomalous Hall conductivity (AHC) is found to be 35 S/cm, which is considerably larger than the theoretically predicted value for ordered Mn2CoAl. Our first-principle calculations conclude that the anti-site disorder between Mn and Al atoms enhances the Berry curvature and hence the value of intrinsic AHC, which is in a very well agreement with the experiment.

This paper focuses on selecting optimal process parameters for uniform single-layer weld bead deposition and the characterization of structures manufactured by GMAW-based wire arc additive manufacturing (WAAM) process. The results reveal that the obtained grain structures vary due to the local thermal cycle. Near to the base of the fabricated part, ferrite with pearlite structures is observed. At the same time, the observed grains become coarser along the deposition direction. Again adjacent to the final layer, finer grains are observed with ferrite and thin strips of bainite, which has been confirmed through XRD analysis. Also, the formation of different chemical compounds such as ferrite, cementite, bornite, and martensite has been identified at different layers. Investigations of surface defects using dye penetration test and corrosion behavior of the component using the weight loss method have also been conducted. The observed surface defects like cracks and porosity are primarily present in the interface of the upper layers. The measured Vickers micro-hardness is found different in different wall structures. The micro-hardness values in the flat and circular wall are recorded as 162.806 HV and 172.191 HV, respectively.

In the present study, continuous wave fiber laser of 400W capacity with CNC controller is used for the cladding operation. SS316 +WS2+Cr powder mixture is taken as clad materials and SS316 of 5 mm thick plate as substrate materials. A homogeneous powder mixture is pasted over the substrate surface and laser beam is scanned by imparting motion to the XY table to get required cross-section area of the clad surface. By adjusting the (±) z–axis of working table the required size of spot diameter (divergence of laser beam) is obtained. For getting the required scan cross-section area, a CNC programmed was built with the help of SINUMERIK 828D SIEMENS controller. A gas chamber made of perpesx sheet having quartz window with different gas purging facility is used to creating required working environment. The laser beam is passed through a quartz window and strike on the surface of the powder layer. Various input process parameters were consider during the experiment such as laser power: 100-200 W, scanning speed: 500-1000 mm/min, % v/v composition of WS2: 5-15 and % v/v composition of Cr: 10 considered as variable process parameters and laser spot diameter: 0.4 mm, hatching gap: 0.2 mm, powder layer thickness: 0.7 mm. The prepared clad specimens were cut with the help of wire-EDM machine for characterization purpose. Then the sectioned specimens were polished using emery paper of different grit size followed by diamond paste polishing to get mirror finishing. Field emission scanning electron microscope (FESEM) (Model: Supra 55, Make: Zeiss, Germany) was used to study the microstructure and to do the elemental analysis. X- Ray diffraction (XRD) technique was used for phase analysis. The diffraction angle (2θ) was kept in the range of 20°-120° to detect the range of chemical compounds formed during the laser cladding process. From XRD analysis, it is can be observed that different intermetallic compounds were formed during laser cladding operation such as WS2, FeS2, FeS, CrS. The micro-hardness of the sectioned surface was measured along the clad depth using a Vickers micro hardness tester (Model: Economet VH-1 MD, Make: Chennai Metco, India). The dry sliding wear behaviour of the clad samples was analysed using a pin on disk tribometer (Make-DOCUM, India, Model: TR 201LE). The wear tests were conducted at an angular speed of 500 rpm at a radial distance of 60 mm. A dead load of 3kgf was maintained during the test for a period of 10 minutes