Thermo-mechanical modeling of residual stress and filler metal optimization for SiC cladding joints

Effect of Mg-rich filler metal on weld zone properties in pulsed laser-welded ultra-fine grain AA6061: A Taguchi optimization study

Tailoring Boride Formation and Strength–Toughness Balance in Dissimilar Superalloy Joints With Ni–Pd-Based Brazing Filler Metals

Dissimilar joining of TiAl alloy to Ni-based superalloy using a Ni-Co-Fe-Mn-Cr-Ge-(Si, B) high-entropy alloy as brazing filler metal

The accumulation of plastic waste poses a severe environmental issue, and efficient depolymerization of plastic is essential toward sustainable waste management and circularity. However, depolymerizing polyolefin plastic into monomer with high selectivity remains a challenge. Herein, inspired by the incandescent light bulb, we demonstrate a catalytic depolymerization strategy utilizing high-temperature transition metal filaments to convert polyolefin plastic to olefin monomer, with monomer selectivity reaching up to 65%. The electrified transition metal filaments, serving as localized heat sources, can reach a high temperature of up to 2300 °C, significantly promoting the generation of gaseous products. The reaction region with sharp temperature gradient restrains secondary transformations of monomer. Monomer selectivity is tunable by varying different high-melting-point metallic elements, and can be extended to bulk commodity alloy, such as stainless steel.

The recent emergence and discovery of new ceramic ion conductors (CICs) with fast ionic conductivity at near-ambient temperatures creates the opportunity to push the frontiers of electrochemical energy conversion and storage. The ability to replace traditional liquid electrolytes with ceramics has the disruptive potential to improve safety and enable next generation technologies including solid-state batteries with metal anodes and impermeable membranes to prevent crossover in redox flow batteries for long-duration energy storage (LDES). Enabling the next generation of electrochemical conversion and storage, however, requires fundamental research to understand and control the emergent mechano-chemical environments that arise when CIC materials are interfaced with other dissimilar materials.The underlying physics that control the stability and kinetics of all solid-state interfaces are fundamentally different from interfaces in state-of-the-art Li ion technology. Moreover, the mechano-electrochemical phenomena that occur during discharge and charge at the Li-CIC interface are considerably different. For example, during charging at higher rates Li metal filaments can initiate at defects and propagate through relatively hard ceramics. During discharge, if the Li stripping rate is sufficiently high and the pressure and temperature is sufficiently low, voids form at the interface causing current focusing and eventual permanent degradation.The United States Department of Energy is supporting the collaborative and interdisciplinary project Mechano-chemical Understanding of Solid Ion Conductors (MUSIC – Figure). The overarching scientific mission of MUSIC is to reveal, understand, and model, and ultimately control the chemo-mechanical phenomena underlying the processing and electrochemical dynamics of CICs for clean energy systems. This presentation will consist of highlights from MUSIC to include topics such as anode-free manufacturing and operando impedance spectroscopy to analyze mechano-electrochemical phenomena at the Li-CIC interface.

Friction-Induced Deposition of a Functional Titanium Coating on Oxide Ceramics for Subsequent Brazing with Metallic Filler Alloys

The application of high strength structural steels in welded structures is growing steadily and intensively. Quenched and tempered (Q+T) as well as thermomechanically treated (TM) steel base materials are developing faster than the filler metals for fusion welding processes, and therefore the selection of filler metal deserves special attention. Welded structures made of high strength steel are often subjected to cyclic loading, which can cause initiation and propagation of fatigue cracks and can lead to fatigue fracture failure of the structural element or the structure. This characteristic must also be taken into account when selecting the filler metal. In order to study this issue, welded joints were made from base materials in the 700-1300 MPa strength category using gas metal arc welding (GMAW) process. The applied filler metals were of the undermatching, matching or overmatching type, depending on the strength of the base material. Fatigue crack propagation (FCP) tests were performed on specimens machined from the welded joints, in which notch locations and crack propagation directions were statistical in nature. Therefore, the fatigue crack propagation directions were parallel and perpendicular to the longitudinal axis of the welded joints and located in different zones of the heat affected zone (HAZ). From these investigations, the two parameters (C and n) of the Paris-Erdogan equation were determined for each specimen and statistical samples were formed from the base material-filler metal matching pairs. During the evaluation of the results, it was found that the matching phenomenon has significant effect on the fatigue crack propagation behavior of the welded joints and that this effect depends on the strength category of the base material. Based on these results, recommendations for the applicable base material-filler metal pairings were proposed.

This study investigates the design and experimental evaluation of Fe–B–Si-based bilayer composites engineered for dual shielding against gamma rays and thermal neutrons. The materials integrate a boron-enriched amorphous Fe matrix with surface coatings of high-Z fillers—lead (Pb) and tungsten (W)—dispersed in an epoxy resin. W or Pb powders (20–40 µm) were dispersed in epoxy resin at a high filler loading (60–70 wt% metal, approximately several tens to one by weight). This ensured a dense and uniform coating structure. The metallic fillers were high-purity (≥99.9%) powders. Gamma-ray attenuation was examined using 137Cs and 60Co sources at photon energies of 661.7, 1173, and 1332 keV, while thermal neutron shielding was assessed with a moderated Am-Be neutron source. The effects of boron concentration (13–21 at%) in the matrix and coating thickness (80–400 μm) were systematically evaluated. Increasing boron content markedly enhanced thermal neutron attenuation, reaching up to 29%, whereas Pb- and W-filled coatings achieved more than 85% gamma-ray attenuation at 661.7 keV. All measurements were repeated three times; standard deviations were below 2% across conditions, confirming reproducibility and indirectly indicating uniform coating dispersion. At 661.7 keV, the half-value and tenth-value layers (HVL/TVL) were derived from the measured linear attenuation coefficients to benchmark performance. Notably, W coatings delivered shielding efficiency comparable to Pb while offering advantages in environmental safety, mechanical robustness, and regulatory compliance. These results highlight the potential of Fe–B–Si bilayer composites as lightweight, scalable, and lead-free shielding materials for aerospace electronics, portable radiation protection devices, and modular panels for satellites and nuclear facilities.

Abstract Understanding the fracture mechanisms in brazed joints offers opportunities to improve joint design and brazing processes. Traditional ex-situ methods cannot capture the material behavior in real-time, making in-situ observation during mechanical testing, such as in SEM, invaluable. In the present work, in-situ bending tests were used to observe the crack propagation in brazed joints exhibiting both ductile and brittle fracture mechanisms. Samples were prepared with precise geometries and notched to initiate cracks in the joining zone. These in-situ tests provide valuable data on the mechanical behavior of brazed joints, offering insights into their failure processes. Three different joints were analyzed: AISI 304 brazed with AgCu filler metal, Mar M 509 brazed with Co-based filler metal and mixed joints of AA 6082 and AISI 304 brazed with AlGeSi filler metal. In the medium strength joint brazed with Ag 272 filler metal, the fracture occurred by slipping through the eutectic. In the high strength joint brazed with Co 900 filler metal, the crack propagated transgranularly through the intermetallic phases and stopped at the interface between the intermetallic and Co solid solution. The AA 6082 / AISI 304 joint was studied using an overlap geometry, showing that microcracks formed as the bending stress increased, finally leading to a failure at the Al 7 Fe 2 Si intermetallic layer, a critical microstructural feature. The used test procedure is suitable for further observations on the fracture mechanism in joints brazed in specific geometries as well as using different brazing process parameters and comparing the results with existing investigations.

The properties of flux-cored Zn-Al filler metals are prone to deteriorating due to corrosion, making filler metals unusable. In this study, flux-cored Zn-2Al-xGe (x = 0, 0.3, 0.5, and 0.8 wt.%) filler metals are prepared to explore the effect of minor Ge on the corrosion resistance of Zn-2Al filler metals. The salt spray test is carried out on filler metals. A scanning transmission electron microscope is used to identify the phases in filler metals. The electrochemical performance of filler metals was tested by a workstation. The findings indicate that the microstructure of the Zn-2Al filler metal is composed of α-Al and η-Zn. Diamond-Ge forms in the microstructure of the Zn-2Al filler metal due to the introduction of Ge. Zn-2Al-xGe filler metals exhibit pitting corrosion characterized by intergranular corrosion (IGC) in the salt spray environment. Ge improves the IGC resistance of filler metals by changing the distribution of α-Al in the filler metal. The Zn-2Al-0.3Ge filler metal demonstrates the most excellent corrosion resistance. It has 16% elongation after 15 d of corrosion, which is higher than that of Zn-2Al by 13.6%.

This study compares the performance of ENiCrMo‐4 and E308L wires in automatic vacuum arc welding for joining dissimilar A352 and A738 steels in cryogenic pressure vessels. Microstructural analysis and mechanical tests investigate the properties of the joints and their relationship with cooling rate and welding parameters. Due to the 2 mm thickness difference between A352 and A738, the cooling rate on the A352 side is ≈179% higher than that on the A738 side. This difference in cooling rate affects the diffusion layer width and the weld microstructure. In comparison, the ultimate tensile strength (UTS) and yield strength of the joint with ENiCrMo‐4 wire (S1) are 1.4 and 2.4% higher than the UTS and yield strength of the joint with E308L wire (S2), respectively. In the cryogenic impact test, the impact energy of S1 is 69 and S2 is 61 J, which shows a 13% advantage in impact energy for S1. This advantage is due to the stronger bond between Ni atoms compared to Fe atoms because the ratio for nickel is 9% higher than that of iron. This study shows that ENiCrMo‐4 wire is a more suitable option for welding cryogenic pressure vessels than E308L wire due to a 13% improvement in impact properties.

This study investigates the structural and mechanical behavior of advanced metal-polymer composite laminates, obtained by combining of aluminum alloy sheets, aramid-reinforced epoxy matrices, and functional metallic fillers. Two complementary approaches are explored: one focusing on the impact response under localized low-velocity shock energy, and the other on structural enhancements achieved through incorporation of high-entropy alloy (HEA) nano-powders. The research process of fabrication the covers of fiber-metal laminates (FMLs) using aluminum alloy layers, aramid fabric with varying surface densities (200 g/m² and 350 g/m²), and an epoxy resin matrix. In one experimental setup, 16 layers of aramid fabric were arranged in a ∅ 70 mm, 4 mm-thick disc, interleaved with three aluminum sheets to create a balanced laminate structure. These specimens underwent low-velocity impact testing (

TA2 titanium was brazed with a Ti–37.5Zr–15Cu–10Ni filler metal at 860–890 °C for 20 min to investigate the influence of temperature on joint properties. Raising the brazing temperature reduced residual filler in the seam center and transformed the microstructure from heterogeneous phases to a uniform α-(Ti,Zr) solid-solution matrix, accompanied by significant widening of the diffusion layer. At brazing temperatures of 890 °C, the hardness decreased to below 300 HV0.5 and became more uniform as brittle phases were suppressed. The shear strength reached a maximum of 302 MPa, and the fracture morphology exhibited characteristics of ductile fracture. Micro-electrochemical testing indicated that the joint brazed exhibited an almost uniform current distribution and significantly reduced localized corrosion. Although a small fraction of the Widmanstätten structure was observed at this temperature, it did not impair the overall mechanical performance. These findings demonstrate that a moderate increase in brazing temperature promotes elemental diffusion, alleviates brittle phase enrichment, and markedly enhances the mechanical properties and corrosion resistance of TA2 joints.

Bending fatigue behavior and microstructure on the T-shaped ferritic stainless steel joints brazed with Ni-Cr-Si-P filler metal

Gas Metal Arc Welding (GMAW) is a welding technique widely used in industry due to its efficiency and ability to produce high-quality weld joints. In this process, the selection of filler metal is an important factor that affects the mechanical properties and microstructure of the weld. One type of filler used is ER307, which is a high manganese stainless steel-based austenitic welding wire designed to join dissimilar metals or steels with high carbon content. The use of ER307 in the GMAW process provides advantages in increasing crack resistance and toughness of the weld, especially in joints that experience high stress or extreme environmental conditions. This study aims to identify the ER307 electrode in the Gas Metal Arc Welding (GMAW) process against the physical and mechanical properties of MIL-DTL-46100E armor steel. Characterization is carried out through EDS tests for microstructure observation, and Vickers hardness tests. The results show that the highest hardness value is in the HAZ zone (523 HV), while the weld metal reaches 324–328 HV, according to Defense Standard 03-34. The content of Mn and Ni in ER307 increases the combination of strength and ductility, while Zn plays a role in corrosion resistance. Thus, ER307 is proven to meet the requirements for welding armor steel for defense applications. The results show differences between the weld metal areas with higher hardness values. The influence of the welding process causes microstructural changes, especially in the HAZ area where the phase is dominated by the ferrite phase. Evidence of material strength in ER 307 electrodes has unique chemical properties by containing elements Manganese (Mn) and nickel which help improve the combination of strength and ductility of the material, and Zinc which has the property of protecting the material from corrosion to strengthen the properties of the joint material in accordance with the steel strength guidelines.

Machining of hardfacing-welded surfaces is a significant engineering challenge in reference to controlling cutting forces and achieving the desired surface quality. The heterogeneity and hardness variations in the material structure after welding can lead to fluctuating cutting forces and irregular surface roughness during the turning process. Therefore, optimizing cutting parameters, tool geometry, and cooling conditions is a critical requirement for enhancing process efficiency and improving the quality of the finished surface. It is important to use both experimental and analytical methods to model cutting forces and surface roughness in order to figure out what factors affect the process and what the best machining conditions are. This study examined the surface roughness (Ra) and cutting force (F R ) produced when three different hardfacing welding metals with varying hardness levels were turned. Three different filler materials, three different feed rates, and three different cutting speeds were used in the machining experiments. The experimental results have demonstrated that the hardness of the filler metal significantly affects F R and Ra. The lowest F R values (66 N) were observed during the machining of the FCH 330 hardfacing material, while the lowest Ra values (0.35 µm) were obtained during the machining of the FCH 355 hardfacing material. Furthermore, the cutting speed of 180 m/min and the feed rate of 0.05 mm/rev produced the lowest values in both machining outputs. F R and Ra were optimized using the Taguchi-based MOORA method. As a consequence of the optimization, the optimal conditions were determined as the FCH 355 filler material, a feed rate of 0.05 mm/rev, and a cutting speed of 180 m/min. ANOVA analysis revealed that F R was affected by both the filler material and feed rate, while Ra was affected only by the feed rate. The developed models showed strong agreement with experimental data and provided accurate predictions.

Achieving excellent mechanical properties of FSW steel/Al joints via the addition of a novel Al-Si-Cu-Ni-La filler metal

A designed FeCoNiCuTiV high-entropy filler metal toward achieving superior interfacial bonding Ti2AlNb alloy

Microstructure, corrosion behavior and mechanical properties of 1Cr18Ni9Ti 1 stainless-steel joints brazed with BNi-2 filler metal