The research team, working across French institutions, built a coupled thermo-metallurgical-mechanical finite element model of tungsten inert gas (TIG) welding on S355J2N steel plates. What sets the work apart is its systematic decomposition of transformation-induced plasticity, or TRIP, the extra plastic strain that arises when steel changes its crystal structure while under stress. Previous simulations often ignored phase transformations entirely or included them only partially, treating the associated volumetric strains while neglecting TRIP altogether. The new study shows that this omission can inflate predicted residual stresses dramatically, potentially leading designers to underestimate the fatigue performance of real welded assemblies.

The experimental foundation of the study was meticulous. Six identical S355J2N specimens, each consisting of two plates measuring 100 by 50 by 15 millimeters joined in a butt configuration, were welded under identical conditions: 200 amperes of current, 14 volts of arc voltage, a travel speed of 2 millimeters per second, pure argon shielding, and no filler metal. Type-K thermocouples recorded the thermal cycles at 50 hertz, while optical microscopy and scanning electron microscopy mapped the microstructures of the fusion zone and the heat-affected zone. Three specimens had to be excluded from the thermal analysis because their thermocouples shifted during welding, a candid limitation the authors acknowledge, but the three retained welds showed cooling-time repeatability within one second.

On the modeling side, the arc’s heat input was represented by the Goldak double-ellipsoid model, whose parameters were calibrated from the measured fusion zone geometry: a half-width of 6 millimeters and a half-depth of 3 millimeters. Diffusive transformations among austenite, ferrite, pearlite, and bainite were described with the V. I. Machnienko model, while the diffusionless martensitic transformation followed the Koistinen-Marburger relation. The mechanical response used a temperature-dependent elastic-plastic von Mises formulation with isotropic hardening, implemented in Abaqus through custom subroutines handling the moving heat source, phase evolution, and stress integration. The mesh contained 67,650 elements, refined down to half a millimeter near the weld.

The thermal validation was convincing. Predicted peak temperatures matched the six thermocouple measurements with errors below 7 percent, and the cooling stage was reproduced with good accuracy, although the cooling time between 800 and 500 degrees Celsius was overestimated by roughly 12 to 14 percent at the two hottest measurement points. The metallurgical predictions fared well too: the model identified bainite as the dominant phase in both the fusion zone, at about 44 percent, and the heat-affected zone, at about 32 percent, exactly as the electron microscope images confirmed. Martensite remained a minor constituent, and the predicted hardness of roughly 240 Vickers in the heat-affected zone sits comfortably below the 380 HV10 limit recommended by the relevant ISO standard.

The heart of the paper lies in its comparison of seven mechanical modeling configurations. Approach A2, which neglects transformation strains entirely, predicted peak longitudinal residual stresses of 632 megapascals on the surface and 760 megapascals through the thickness, values approaching the steel’s yield strength. Adding only the volumetric strain of phase transformations, approach A1, trimmed those peaks by 21 to 35 percent. But the complete model, A4, which adds TRIP, cut the through-thickness peak to 473 megapascals and the region-averaged longitudinal stress from 641 to 280 megapascals, a reduction of more than half. Volumetric strain alone, in other words, tells only a fraction of the story.

Even more striking was the decomposition of TRIP itself into three distinct contributions: classical plasticity driven by stress variations, plasticity driven by temperature variations, and plasticity driven by the rate of change of phase fractions. When each term was isolated, the phase-fraction term emerged as the overwhelming driver of stress relaxation. On the surface path, it reduced the mean longitudinal stress by 51 percent, nearly matching the 53 percent achieved by the complete model, while the stress-only term managed just 9 percent. This finding is qualitatively consistent with the theoretical estimate of Leblond and colleagues, who calculated that plasticity from phase fraction variations could be roughly 25 times greater than that from temperature variations during martensitic transformation.

The study also quantified a subtler effect: the evolution of the effective yield stress during cooling, computed as a phase-weighted average of the individual phase yield stresses. Keeping the yield stress identical during heating and cooling, as many earlier simulations did, raised the predicted peak stress by about 8 to 24 percent compared with accounting for its evolution. Sensitivity analyses reinforced the robustness of the conclusions: plausible variations in high-temperature thermal properties, mesh refinement, and high-temperature mechanical assumptions shifted the mean longitudinal stress by at most a few percent, whereas the TRIP activation threshold proved to be the single most influential parameter, changing predicted stresses by up to 32 percent.

Transverse residual stresses, by contrast, remained much lower than the longitudinal ones, peaking at 178 megapascals on the surface and 384 megapascals through the thickness for the complete model. The authors attribute this asymmetry to the greater plastic deformation the plate undergoes in the transverse direction and to the narrow width of the weld bead relative to its length. The longitudinal dominance aligns with trends reported in earlier studies of arc-welded joints, including work showing that tensile residual stresses in tubular K-joints can drive fatigue cracks to half the chord thickness even under nominally compressive loading.

The practical implications are significant for anyone designing or fabricating welded steel structures. Models that ignore TRIP may substantially overestimate residual stresses and thereby underestimate fatigue performance, potentially triggering unnecessary post-weld treatments or overly conservative designs. Conversely, the finding that the phase-fraction term governs relaxation gives modelers a clear target: capturing transformation kinetics accurately matters more than refining thermal parameters. The authors caution that direct experimental validation of the residual stresses is still pending, with X-ray diffraction measurements on reserved specimens planned for a forthcoming study, along with Vickers microhardness validation and a dedicated investigation of the contact conductance between plate and welding table. Until those results arrive, this work stands as a compelling demonstration that the invisible drama of phase transformations inside cooling steel is not a modeling nicety but the decisive factor in predicting the stresses that determine whether welded structures endure.

Subject of Research: Thermo-mechanical modeling of residual stresses and transformation-induced plasticity in TIG-welded S355 structural steel joints

Article Title: Thermo-mechanical modeling of residual stresses in TIG-welded S355 steel joints

Article References: Niangaly, I., Abdennadher, M., Zouari, S., Leprêtre, E., & Dieng, L. (2026). Thermo-mechanical modeling of residual stresses in TIG-welded S355 steel joints. Results in Engineering, 32, Article 113233. https://doi.org/10.1016/j.rineng.2026.113233

Image Credits: AI Generated

DOI: 10.1016/j.rineng.2026.113233

Keywords: residual stress, TIG welding, S355 steel, phase transformations, transformation-induced plasticity, TRIP, finite element modeling, bainite, martensite, fatigue, heat-affected zone, structural steel

The launch of the Journal of Materials Science: Metallurgy, a sister title to the long-established Journal of Materials Science, marks a deliberate return of focus to metals after decades in which the broader field of materials science absorbed and expanded upon metallurgical principles. The inaugural editorial, written by Sophie Primig of UNSW Sydney and Megumi Kawasaki of Oregon State University and published in November 2025 as the first article of the journal’s first volume, sets out why the editors believe metallurgy is once again at the frontier of science rather than a mature discipline resting on its laurels. Their argument rests on simultaneous breakthroughs in four areas: alloy design, processing, characterisation, and performance in extreme environments.

To understand why this moment matters, it helps to trace the intellectual lineage of the field. Metallurgy is often described as one of the oldest sciences, with origins stretching back more than 6,500 years, yet its modern scientific form crystallised in the twentieth century. By the mid-1900s, researchers had begun applying metallurgical principles, particularly those governing phase transformations, thermodynamics and the structure of crystalline solids, to ceramics, polymers and semiconductors. That expansion gave birth to materials science and engineering as an inherently interdisciplinary field, one that integrates physics, chemistry and engineering within a unifying framework known as the processing-structure-property-performance relationship, frequently visualised as the materials science tetrahedron. Each corner of that tetrahedron constrains and enables the others: change how a material is processed and you alter its internal structure, which in turn dictates its properties and ultimately its real-world performance.

The Journal of Materials Science itself was founded in 1966 by Robert W. Cahn, a distinguished physical metallurgist celebrated for his work on the thermodynamics and kinetics of phase transformations in solids. Under his influence the journal quickly became a leading platform for the rapidly growing materials community, and like metallurgy itself it has continued to thrive while broadening its scope to encompass every class of material. The new sister journal reverses that expansion, narrowing the aperture deliberately to metals and alloys at precisely the moment when the field’s rate of discovery is accelerating. The editors describe their aim as capturing a new era of discoveries in one of humanity’s most foundational and continually evolving sciences.

The first engine of that new era is a revolution in alloy design. For most of history, metallurgists worked with alloys built around a single dominant element, with smaller additions of other elements tuned to refine properties: iron with carbon and chromium to make stainless steel, aluminium with copper or lithium to make aerospace alloys, nickel with cobalt and refractory metals to make superalloys. That paradigm is now being challenged by multiple principal element alloys, often called high-entropy alloys, in which four, five or more elements are mixed in near-equal proportions. Because these compositions occupy vast, previously unexplored regions of chemical space, they access property combinations that conventional alloys cannot reach, from exceptional strength at cryogenic temperatures to remarkable resistance to softening at high temperature. Alongside them sit metallic glasses, amorphous metals whose disordered atomic structure confers extraordinary elasticity and corrosion resistance, and, most strikingly, alloy compositions generated by artificial intelligence algorithms that no human designer would have proposed.

The second engine is a rethinking of processing itself. Traditional thermomechanical routes, the carefully choreographed sequences of heating, deformation and heat treatment that metallurgists have refined over generations, are being joined by radically new techniques, most prominently additive manufacturing. When a metal component is built layer by layer from a melt pool measured in fractions of a millimetre, the solidification behaviour, the welding metallurgy and the non-equilibrium solid-state phase transformations all depart from textbook expectations, forcing researchers to reassess fundamental assumptions about how microstructures form. At the same time, sustainable metallurgy is emerging as a design philosophy rather than an afterthought: circular processing routes that recycle alloys with lower environmental footprints, and more ethical stewardship of limited natural resources, are becoming central criteria for how new materials and processes are judged.

The third engine lies in how scientists see and measure metals. Advanced multiscale characterisation now spans from in-situ methods that watch components deform or transform under realistic loads at the laboratory scale, down to atomic-resolution imaging and diffraction that reveal individual dislocations, solute clusters and grain-boundary chemistry. Crucially, this experimental knowledge is increasingly coupled with multiscale modelling and simulation, allowing researchers to connect what happens at the scale of a nano-sized precipitate to the behaviour of an entire turbine disc. The prediction of processing-microstructure-property relationships using machine learning, validated against targeted experiments, is described in the editorial as an emerging and rapidly growing field, one that promises to compress development cycles that once took decades into years or even months.

The fourth engine is the relentless push into extreme environments. Alloys are now engineered to combine superior high-temperature strength with ductility, a combination that has historically involved difficult trade-offs because the microstructural features that resist deformation at high temperature often embrittle the material. Add exceptional corrosion and degradation resistance, and the resulting materials are redefining what the editors call extreme materials can achieve in demanding applications, from hypersonic flight and next-generation nuclear reactors to hydrogen infrastructure and deep-earth energy extraction. Each of these applications demands metals that survive conditions, temperatures, stresses and chemistries, that would destroy conventional alloys within hours.

Against this backdrop, the new journal positions itself as a dedicated platform for high-quality, original research that advances fundamental understanding of metals and alloys. The editors state a particular preference for interdisciplinary studies that integrate modelling, novel experimental approaches and advanced analytical techniques, and they explicitly welcome both work that extends current fundamental understanding and breakthroughs arising from collaboration between industry and academia. That dual emphasis reflects a practical reality of modern metallurgy: the distance between a laboratory discovery and an engineered product remains long, and closing it requires simultaneous progress in theory, experiment and manufacturing practice.

What emerges from the editorial is a portrait of a discipline that is neither nostalgic about its ancient roots nor complacent about its achievements. The materials science tetrahedron that unified the field in the twentieth century still holds, but every corner of it is being redrawn at once. Compositions once dismissed as thermodynamic curiosities are being screened by algorithms and confirmed in the laboratory; components are being solidified under conditions that classical theories never anticipated; microscopes and simulations are converging on the same atoms from opposite directions; and the alloys that result are expected to work where no metal has reliably worked before. For a science older than the pyramids, metallurgy appears to be entering its most dynamic chapter yet, and the research community now has a venue built specifically to document it.

Subject of Research: The launch of a new metallurgy journal and the advances in alloy design, processing, characterisation and extreme-environment performance driving a new era in metallurgical science

Article Title: Editorial: Journal of Materials Science: Metallurgy

Article References: Primig, S., & Kawasaki, M. (2025). Editorial: Journal of Materials Science: Metallurgy. Journal of Materials Science: Metallurgy, 1(1), Article 1. https://doi.org/10.1007/s44492-025-00001-x

Image Credits: AI Generated

DOI: 10.1007/s44492-025-00001-x

Keywords: metallurgy, materials science, high-entropy alloys, alloy design, additive manufacturing, machine learning, sustainable metallurgy, microstructure, phase transformations, extreme environments, metallic glasses, Journal of Materials Science