This study explores the joining of AA6061-T6 aluminium alloy and AZ31B magnesium alloy using the Cold Metal Transfer (CMT) process with ER4043 aluminium filler wire. The influence of wire feed speed (WFS), welding speed (WS), and arc length correction (ALC) on weld bead geometry, microstructure, and mechanical properties of Al/Mg joints was investigated. The results indicate that WFS, WS, and ALC significantly affect weld characteristics. Increasing WFS leads to higher heat input, improving reinforcement height, penetration, and bead width. At 4700 mm/min WFS, optimal reinforcement height was achieved, while 5000 mm/min further enhanced penetration and bead width. Higher WS reduced heat input, resulting in narrower bead width, shallower penetration, and lower reinforcement height. ALC influenced arc behaviour, with 10% ALC minimising the weld metal area and 15% significantly increasing it. Microstructural analysis identified MgO, Mg solid solution, Mg2Al3, and Mg17Al12 at different joint regions. The optimized parameters (4700 mm/min WFS, 280 mm/min WS, 10% ALC) yielded the highest tensile strength of 34 MPa and hardness of 120 HV. Fracture occurred mainly at the Mg/weld interface and near the fusion line. This study underscores the importance of welding parameters in enhancing the mechanical properties of Al/Mg joints and provides insights for optimising aluminium-magnesium welding.

This study demonstrates the stabilization of Mg-3Ca foams by ex-situ addition of TiB2 particles (D50 = 8.045 μm) as effective agents to enhance foam morphology and stability. TiB2 additions (3 and 5 vol%) delayed cell coarsening and preserved higher circularity by increasing melt viscosity. While Mg-3Ca foams contracted during prolonged foaming (5–15 min), TiB2-containing foams retained and even enhanced their expansion, achieving volumes of 625 % and 652 % compared to 566 % for the base alloy. A single-film stabilization model revealed thicker and smoother films (130 μm to 323 μm) with reduced oxide accumulation in the presence of TiB2 particles, highlighting their role in enhancing foam longevity. Quasi-static compression tests indicated that higher TiB2 content introduced serrated deformation, slightly reducing energy absorption. These findings advance our understanding of particle-stabilized Mg foams, offering new opportunities for lightweight, high-performance materials

In many space exploration missions, where precise trajectory control is essential for successful operations, space robotics plays a critical role. This paper uses bond graph modeling to describe the dynamics of the system and to efficiently apply control schemes. This modeling method provides a strong framework for examining the behaviour and interactions of systems. Although bond graph modeling and Proportional-Integral-Derivative (PID) control are frequently combined, PID controllers frequently perform less than optimally in complicated or nonlinear systems. The controller parameters are optimized using Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) to get over this restriction. GA simulates the process of natural selection and evolution while, PSO a population-based optimization method, imitates the behaviour of a swarm. The goal of both algorithms is to determine the PID parameters in order to reduce trajectory errors and improve efficiency. This study presents an enhanced capability for redundant space robots to manage their trajectory during contacts with free-floating objects by merging PID with PSO and GA respectively.

This study investigates the development of grain structure and crystallographic texture in Inconel 825 parts produced via wire arc-based additive manufacturing. Microscopy revealed distinct dendritic morphologies across the build height, transitioning from refined cellular and equiaxed structures near the substrate to coarser columnar dendrites in the upper layers due to reduced cooling rates. Electron backscatter diffraction (EBSD) analyses indicated a strong crystallographic texture with preferred 〈111〉 and 〈001〉 orientations along the build direction. The grain boundary character distribution showed a high fraction of high-angle grain boundaries (45%), suggesting potential for superior mechanical performance. Pole figure analysis confirmed orthotropic texture symmetry, highlighting the directional nature of solidification and epitaxial growth. These texture-induced microstructural features contribute to superior load-bearing capability and thermal stability, making WAAM-fabricated IN825 well-suited for demanding applications in aerospace, chemical processing, and power generation environments, where high temperature and corrosion resistance are critical.

Wire arc additive manufacturing (WAAM) using the cold metal transfer (CMT) process has emerged as a transformative method for producing near-net-shape metal components with tailored microstructures and enhanced mechanical performance. This study investigates the wear characteristics of components fabricated using CMT-based WAAM with ER70S-6 low-carbon steel (LCS) and 316LSi stainless steel (SS), focusing on their potential for abrasive and erosive wear applications. Microstructural analysis, including phase transformations and grain morphology, was performed in both the deposition (X) and building (Y) directions. Wear testing was conducted on a pin-on-disc machine under varying loads (1.5–3.5 kg) and sliding speeds (150–450 rpm) to evaluate wear rates, coefficients of friction (COF), and wear track morphology. The microstructure of the WAAMed LCS component is characterized by lamellar structures of ferrite and pearlite, with variations observed along the X- and Y-directions. The X-direction shows ferrite structures including polygonal ferrite and Widmanstätten ferrite (αWD), while the Y-direction exhibits acicular ferrite (αac) and bainite (B) phases. The WAAMed 316LSi SS shows austenitic structures with residual ferrite, exhibiting lathy ferrite morphology in the X-direction and vermicular ferrite in the Y-direction. At the highest load and speed, the wear rate of 316LSi SS was reduced by 83.51% compared to LCS, with wear rates ranging from 0.74 × 103 to 1.98 × 103 g/m for 316LSi SS, and from 1.64 × 104 to 2.65 × 104 g/m for LCS. The COF for 316LSi SS remained within 0.34–0.45, significantly lower than the 0.53–0.57 observed for LCS. SEM analysis of worn surfaces identified abrasive, adhesive, and delamination wear as predominant mechanisms for LCS, whereas 316LSi SS showed minimal material loss due to its higher hardness (193–227 HV0.5 vs. 160–187 HV0.5 for LCS) and stable microstructure. These results establish WAAM-fabricated 316LSi SS as a promising material for wear-critical applications, providing a foundation for optimizing processing parameters and material properties.

Property mapping, an indentation technique, was employed to investigate the nano-mechanical behaviour of austenite, ferrite, and interphase regions in duplex stainless steel (DSS). The influence of furnace cooling and water quenching heat treatment processes on the deformation behaviour of individual phase regions was quantitatively assessed in both the transverse and longitudinal sections of DSS samples. Property evaluation across these regions was conducted through load-displacement curves and associated material parameters such as empirical property ratios, elastic-plastic indentation work values, and other mechanical properties. This study reveals the heterogeneous and anisotropic nature of the mechanical behaviour of DSS phase regions across the sections, which can assist in improving structural design(s).

This study investigates the effect of forging pressure on the microstructural evolution, mechanical properties, and fracture behaviour of rotary friction welded (RFW) low-alloy steel (LAS) joints. Three forging pressures - 0.76, 0.84, and 0.91 MPa/s - were applied to evaluate their influence on hardness, tensile strength, and ductility. Microstructural analysis revealed that at 0.84 MPa/s, significant grain refinement occurred in the heat-affected zone, promoting superior mechanical properties. The ultimate tensile strength increased from 473 MPa at 0.76 MPa/s to 488 MPa at 0.84 MPa/s, before slightly decreasing to 482 MPa at 0.91 MPa/s due to grain coarsening. A maximum elongation of 40.01% was achieved at 0.84 MPa/s, representing a 27.05% improvement compared to 0.76 MPa/s. Hardness variations followed a similar trend, with peak values observed at intermediate forging pressure. Fractographic analysis confirmed a ductile fracture mode at 0.84 MPa/s, characterised by deep equiaxed dimples, while coarser fracture features were noted at higher pressures. These results demonstrate that an optimal forging pressure enhances strength-ductility synergy by refining the microstructure and preventing excessive grain growth. The findings provide valuable insights into optimising forging conditions for high-performance RFW LAS joints in structural and industrial applications.

This study investigates the impact of printing orientation on the mechanical properties and surface characteristics of parts produced using VeroWhitePlus RGD835 polymer material in a layer-based Polymer Jetting Technology process. Tensile, hardness, and surface roughness tests were conducted to evaluate the influence of different printing orientations on the properties of the printed samples. The results show that printing orientation significantly affects both the mechanical strength and surface roughness of the parts. Specifically, samples printed in the XZ, YZ, and vertical orientations exhibited 20–30% higher tensile strength and 15–25% greater hardness compared to those printed in XY and other orientations. Surface roughness values varied by up to 10 µm across orientations but did not directly correlate with tensile strength and hardness, suggesting a complex interaction between orientation, layer bonding, and material properties. This anisotropic behavior is attributed to the non-uniform absorption of light energy during the jetting process, which causes varying layer bonding and material density across different regions of the printed parts. Additionally, areas with higher energy absorption, such as the edges of layers, exhibited smoother surfaces and enhanced mechanical properties, while regions with lower energy absorption showed rougher surfaces and reduced strength. Fracture surface analysis revealed brittle fracture characteristics with localized pressures and voids between layers, weakening the material’s ability to withstand deformation. These findings provide valuable insights into the optimization of Polymer Jetting Technology processes, particularly in selecting printing orientations and adjusting process parameters such as light exposure intensity, to improve mechanical performance and surface quality.

To address the challenges of heat input in wire arc additive manufacturing (WAAM), this study employed the pulsed cold metal transfer (PCMT) technique to fabricate Incoloy 825 (IN825) components. PCMT, characterized by controlled droplet transfer and reduced heat input, enhanced mechanical performance and microstructural quality. Comprehensive analyses, including microstructural examination, X-ray diffraction, energy-dispersive X-ray spectroscopy (EDS), and element mapping, were performed. Titanium and molybdenum-rich secondary particles were identified through EDS. The mechanical properties of PCMT-fabricated components were compared with both wrought IN825 and those produced by gas metal arc additive manufacturing (GMAAM). Results demonstrated that PCMT components, particularly those fabricated at a 45° orientation, achieved approximately 113% of the ultimate tensile strength (UTS) and 131% of the elongation compared to wrought IN825. This marked a significant improvement over GMAAM-fabricated components. The reduced heat input and enhanced cooling rates in the PCMT process contributed to finer microstructures and superior mechanical properties. Fractography studies revealed that PCMT components exhibited ductile fractures with significant plastic deformation and some brittle regions. These findings underscored the advantages of PCMT in producing high-performance IN825 components compared to traditional GMAAM.

Direct energy deposition (DED) is an advanced additive manufacturing (AM) technique for producing large metal components in structural engineering. Its cost-effectiveness and high deposition rates make it suitable for creating substantial and complex parts. However, the mechanical and microstructural properties of these components can be influenced by the varying heat input and repeated thermal treatments associated with different welding procedures used during the deposition process. This study employed gas metal arc welding (GMAW) and cold metal transfer (CMT) arc welding techniques to fabricate cylindrical components from 2209 duplex stainless steel (DSS). The research investigated the impact of these welding methods on the microstructure and mechanical properties of the 2209 DSS cylinders. The intricate thermal cycles and cooling rates inherent in the DED process significantly influenced the primary phase balance, ideally comprising 50% austenite and 50% ferrite. In components processed using GMW, σ-phase formation was noted at the grain boundaries. Additionally, a slower cooling rate and extended time for solid-state phase transformations led to an increase in austenite content from the bottom to the top of the component. The cylinder fabricated using the CMT process exhibited fine austenite morphologies and a higher ferrite content compared to the GMW-processed cylinder. Furthermore, the cylinder produced using the CMT process showed consistent properties across the building direction, unlike the components manufactured with the GMW process. In terms of tensile properties, hardness, and impact toughness, the cylinder produced using the CMT technique outperformed the one made with the GMW process.

The proliferation of Wire Arc Additive Manufacturing (WAAM) has significantly enhanced the production capabilities for lightweight and structurally robust components. This study investigates the microstructural characteristics, tensile properties, and preliminary wear performance of AA 5083 aluminum alloy processed via WAAM, focusing on applications for lightweight structures. Using SEM and XRD, microstructural changes during the WAAM process are analyzed, and tensile testing evaluates the mechanical properties, including ultimate tensile strength (UTS) and elongation. The results reveal that the microstructure consists of α-Al and β-(Al5Mg8) phases, with the Al5Mg8 phase distributed along grain boundaries and within grains. Notably, the grain size in the Y-direction (building direction) is larger than in the X-direction (deposition direction) due to temperature variations during processing. Tensile testing shows that horizontal samples (X-direction) have a UTS of 295 ± 5 MPa and elongation of 20.08 ± 0.8 %, while vertical samples (Y-direction) have a UTS of 267 ± 10 MPa and elongation of 16.43 ± 2.1 %. This results in an anisotropy of 9.4 % in tensile strength, reflecting the differences in mechanical properties between the two directions. The WAAM AA 5083 aluminum part exhibits a maximum wear rate of 5.22 × 10⁻³ mm³/m and a coefficient of friction of 0.52 at a load of 3.5 kg and 450 rpm. Under these conditions, deep grooves, layer separation, and load-induced deformation are observed. The primary wear mechanisms include delamination, adhesion, and abrasion. Hardness levels are consistent in the X-direction and show minimal variance in the Y-direction, with an average hardness of 89.4 ± 5.14 HV0.5. The study demonstrates that WAAM-produced AA 5083 aluminum alloy, with an anisotropy below 10 %, is suitable for real-time lightweight structures, offering effective performance in engineering applications such as aerospace and automotive industries. Future research should focus on further quantifying wear behavior and optimizing processing conditions to enhance material performance for specific applications.

The large structural components (304 L austenitic stainless steel) used in nuclear power plants are difficult and expensive to manufacture and machine using standard methods. Wire arc additive manufacturing (WAAM) is a low cost and high deposition method for fabricating large structural parts. Therefore, in this investigation, 304 L austenitic stainless steel (304 L ASS) cylindrical component was fabricated using WAAM technique. The mechanical and microstructural characteristics of the bottom (region ①) and top (region ②) of the WAAM 304 L ASS component are studied. The microstructure of region ① consists of austenite and ferrite with vermicular and lathy morphologies, while region ② consists of skeletal and reticular morphologies. In regions ① and ②, yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) were found to be 350 ± 7 MPa, 562 ± 10 MPa, and 75 ± 1%, respectively. The impact toughness and hardness in regions ① and ② were found to be 112 ± 2 J and 183 ± 6 (Hv0.5), respectively. From the results, it is evident that the tensile properties of the WAAM 304 L ASS component were equal/greater than the values of the forged 304 L ASS material, wrought 304 L ASS alloy, and 304 L ASS filler wire.

This study examines the microstructural, mechanical, and fractographic characteristics of friction-welded (FW) joints between SA 213 T12 and SA 213 F12 low alloy steels at rotational speeds of 55, 60, and 65 rps. Microstructural analysis using optical and SEM imaging revealed distinct weld zones, including the interface (IF), partially deformed zone (PDZ), and heat-affected zone (HAZ). The IF exhibited refined bainite and acicular ferrite, with increased dynamic recrystallization at 60 rps, leading to enhanced mechanical properties. Elemental mapping through EDS confirmed uniform chromium and molybdenum diffusion across the IF, with greater mechanical mixing at higher speeds. Microhardness profiling showed peak values at the IF, particularly on the SA 213 F12 side, decreasing towards SA 213 T12. The hardness distribution narrowed at higher speeds due to increased flash generation. Tensile testing revealed that all joints exceeded the base metals in ultimate tensile strength (UTS), with the highest UTS at 60 rps. Fractographic analysis confirmed a predominantly ductile failure, with finer dimples at 60 rps, correlating with improved elongation and strength. These findings demonstrate that an optimal rotational speed of 60 rps yields superior mechanical performance and microstructural refinement, providing valuable insights for optimizing FW parameters in high-performance applications.

This study investigates the influence of gas tungsten arc welding (GTAW) current modes on dissimilar joints between Inconel 718 and AISI 410 martensitic stainless steel, targeting aerospace applications. Welding these alloys is challenging due to their differing thermal and chemical properties, which lead to brittle Laves phase formation, elemental segregation, and residual stresses. To address this, constant current (CCGTAW) and pulsed current (PCGTAW) techniques were compared. Microstructural characterisation was performed using optical and scanning electron microscopy to examine fusion zones, interfaces, and heat-affected zones. Both weldments showed niobium-rich Laves phases; however, PCGTAW resulted in a lower volume fraction (7.06%) than CCGTAW (10.50%), indicating improved suppression. Tensile failures occurred in the AISI 410 base metal for both welds. Microhardness profiles revealed uniform fusion zone hardness, softening in the IN 718 HAZ, and martensitic hardening in the AISI 410 HAZ. Hot corrosion tests at 650 °C in a K2SO4-NaCl environment showed superior resistance in PCGTAW welds, with lower weight gain, reduced oxide spallation, and a smaller parabolic rate constant (Kp). These enhancements are attributed to grain refinement, reduced segregation, and a narrower partially melted zone. Overall, PCGTAW significantly improves joint integrity and corrosion resistance, making it ideal for aerospace-grade dissimilar welding applications.

Solid oxide fuel cells (SOFCs) receive significant attention due to theirs high efficiency, environmental advantages, and fuel flexibility. The interconnect is a crucial part that connects each cell in the SOFC stack. The High Entropy Alloy (HEA) of FeCoCrNiMn0.5 is a promising candidate for an interconnect material at intermediate temperatures (600 °C to 800 °C) in Solid Oxide Fuel Cells (SOFC) due to its good thermal stability and electrical conductivity. However, FeCoCrNiMn0.5 HEA has a higher coefficient of thermal expansion (CTE) than the other interconnect materials (SUS 430, Crofer 22 APU) in SOFCs such as LSM (Lanthanum Strontium Manganite) cathode and NiO-YSZ anode. The high CTE in an HEA is undesirable as it mismatches with the CTE of cathodes and anodes in SOFC. The present study investigates the thermophysical properties and oxidation behavior of an Nb-contained HEA (Cr21Co21Fe21Ni21Mn11Nb5) to achieve reduced CTE and improved oxidation properties than the existing interconnect HEAs. The novel Cr21Co21Fe21Ni21Mn11Nb5 HEA was produced by the vacuum arc melting technique. The structure, chemical composition, mechanical properties, CTE, and thermal stability of the HEA were investigated. The oxidation study was also carried out by oxidizing the as-cast HEA at 800 °C for 25, 50, 100, and 200 hours. The study revealed that the presence of Nb reduces the CTE, increases oxidation resistance, and improves the mechanical properties of the HEA. The harmful Chromium oxide layer does not appear on the top of the thermally grown oxide layer during oxidation of the HEA. This passivation of the Chromium oxide layer will significantly reduce the Cr-poisoning in SOFC.

Oxide dispersion in high-entropy alloy (HEA) improves mechanical properties, corrosion resistance, and high-temperature oxidation. Several studies have been reported on oxide-dispersed high-entropy alloys prepared by Spark plasma sintering and hot pressing, but only a few on coating. This study aims to investigate a novel Fe-free Co1.7 Cr0.4Ni2.5Al2.4 Nb0.23 HEA dispersed with oxide (1 wt % Y2O3) for bond coat application in the thermal barrier coatings (TBC) System. The elemental powders in desired stoichiometry along with yttria were milled for 5 h in a planetary ball mill with a ball-to-powder ratio of 10:1 at a speed of 300 rpm followed by heat treatment at 1050 C for 1 h in argon. ODHEA bond coat and yttria-stabilized zirconia (YSZ) topcoat was coated by high-velocity oxygen fuel (HVOF) and air plasma spray on a nickel superalloy substrate, respectively. The coating shows the formation of FCC, BCC and Laves phase. The hardness and Young's modulus for the coating were approximately 610 HV and 172 GPa. Good oxidation resistance with an average TGO layer thickness of less than 7 μm was observed after 100 h of isothermal oxidation.

This article introduces a novel class of ∆h-truncated exponential-based Hermite polynomials and examine their fundamental properties and structural identities. We derive generating functions, recurrence relations, and explicit formulas, along with summation identities. The study further uncovers connections with the monomiality principle, offering insights into their underlying algebraic framework. In addition, an operational formalism is developed, and symmetric identities are established to enhance the theoretical foundation of these polynomials.

This study introduces a new class of ∆h Legendre-Laguerre-Appell polynomials, constructed through the synergy of the monomiality framework and operational calculus. A comprehensive exploration is carried out, beginning with the formulation of their generating function, followed by the derivation of explicit representations and recurrence schemes. Notably, a determinantal structure for these polynomials is also established and illustrated through representative examples. The work further investigates how this polynomial family interrelates with well-known ∆h-variants of classical polynomials, including the Bernoulli, Euler, and Genocchi types. Through these connections and properties, the results not only deepen our understanding of the algebraic and analytic behaviour of the ∆h Legendre-Laguerre-Appell polynomials but also highlight their potential applications in broader areas of discrete mathematics and operational theory.

There are attempts to develop a hybrid (S-glass–carbon) composite fan blade which can show excellent damage resistance under bird strike kind of loading. Some part of the carbon fiber composite blade is to be replaced with S-glass and to achieve this, carbon–glass joints need to be optimized. The main technical challenge in this, is the robustness of the interface region between S-glass and carbon plies. The interface region optimization in terms of ply layups and overlaps has been performed and a few promising cases of interlock configurations have been proposed in this context. As part of this interlock region structural evaluation task, representative composite coupons were made, and bird strike impact tests were performed. This article presents the bird strike analysis results of these interlock ply-by-ply coupons and the correlations of these analysis results with the actual bird strike test results performed on these coupons. Overall analysis to test results correlation has been satisfactory and detailed comparisons are shown in this article. The coupon-level bird strike analysis methodology was enhanced by including the resin pockets that results in the interlocking regions. The understanding obtained from this work will be used as guideline for designing and validating the hybrid composite blade for aircraft engines.

Large portion of wind turbine blade is sandwich construction made out of glass fiber/epoxy composite face sheet with foam core. The objective of the current study is to evaluate alternate core materials suitable for blade shell sandwich applications for low cost and low weight. Various commercially available core materials are evaluated analytically for panel level buckling performance and aerial weight for relative comparison of core material. Based on structural and cost analysis, Webcore structural core material is selected for blade shell application and experimentally evaluated for its properties, such as density, shear modulus, compression modulus and tensile modulus, to compare with currently used PVC foam core. Buckling tests of sandwich panel are conducted to evaluate core materials performance for wind blade application. Webcore materials proved to be better candidates for wind blade applications as compared to PVC foam core.