Liquid metal embrittlement (LME) during resistance spot welding (RSW) of Zn-coated twinning-induced plasticity (TWIP) steel results in intergranular cracking driven by the interaction of liquid Zn, tensile stress, and the grain boundary (GB) network. This study investigates how GB misorientation and orientation relative to the electrode force loading axis influence the LME crack path across six weld times from 700 ms to 1700 ms. A comparative framework was developed in which, at each triple junction along the LME crack, the misorientation and angle relative to the loading axis of the chosen LME grain boundary are evaluated against those of the unchosen LME-free grain boundary. Σ3 coherent twin boundaries were LME-free at all weld times regardless of their orientation to the stress axis. Non-twin coincident site lattice (CSL) boundaries (Σ5 to Σ41) were predominantly LME-free at low weld times but progressively became LME GBs at high weld times, when their stress normalisation factor exceeded that of the competing boundary. The fraction of triple junctions where the LME grain boundary had the higher stress normalisation factor increased from 58% at 700 ms to 91% at 1700 ms, while the preference for the higher-misorientation-angle boundary declined from 73% to 56% over the same range. An LME susceptibility index incorporating grain boundary energy, temperature-dependent Zn diffusivity, and stress alignment is proposed as a framework for predicting crack path selection and guiding grain boundary engineering strategies (GBE) to reduce LME in resistance spot welded TWIP steel.

This work aims to clarify the fundamental precipitation mechanisms in the Fe–Al–Mn–C system, spanning from atomic-level processes to the overall mechanical response. A multiscale characterization approach, including high-resolution transmission electron microscopy, atom probe tomography, and synchrotron X-ray diffraction, was combined to characterize the evolution of κ-carbides during aging, providing atomic-level insights into their formation. This enabled the analysis of carbide size, morphology, interparticle spacing, and volume fraction at different stages of aging. Tensile and hardness tests on samples aged at 550 ℃ for different times were performed to correlate macroscale mechanical properties with the nanoscale κ-carbides. The results show that spinodal decomposition occurs throughout the 8 h of aging, forming solute-rich regions. In contrast, the formation of κ-carbides begins in the solute-rich areas through short-range ordering in the early stages of aging, i.e., within 30 min at 550 ℃, and both the fraction and size increase with longer aging times. After 2.5 h of aging, the fraction and lattice parameter of the κ-carbides saturate and stop increasing. The yield strength and hardness follow the same trend as the κ-carbide fraction, with a steep increase in the initial stages of aging, up to 2.5 h, reaching 925 MPa and 360 HV, and then saturating after 2.5 h. This work provides a clear mechanistic understanding of the underlying strengthening mechanisms and the resulting mechanical behavior.

This study investigates the microstructural evolution, crystallographic texture, and mechanical properties of a nickel-aluminium bronze (NAB)/410 NiMo martensitic stainless steel bimetallic structure fabricated via wire arc additive manufacturing (WAAM). The work provides a detailed assessment of the interfacial characteristics, phase transformations, and texture development across both alloys, as well as their impact on mechanical behaviour. Microstructural characterisation using optical microscopy, SEM, EBSD, and TEM revealed that the stainless steel region predominantly consists of martensite with minor fractions of δ-ferrite, α-ferrite, and retained austenite. A distinct Fe-rich interfacial layer was identified, from which columnar dendrites grow epitaxially into the NAB side. The NAB region exhibits α-phase grains with various k-phase precipitates whose distribution and morphology evolve with build height due to thermal cycling and dilution effects. Evidence of liquid metal embrittlement (LME) was observed at the interface. Texture analysis indicated a weak crystallographic texture in the stainless steel due to solid-state transformations, whereas the NAB exhibited a more textured structure, especially <101>//BD. Despite the presence of LME cracks at the interface, tensile testing consistently resulted in fracture within the NAB region, away from the interface, demonstrating effective load transfer across the interface under uniaxial tensile loading parallel to the building direction. The bimetallic structure achieved an ultimate tensile strength of 587 MPa and total elongation of ∼12%.

Crystallographic texture plays a central role in determining the mechanical and functional properties of low-carbon steel sheets. While the γ-fiber 111//ND texture has been extensively studied and effectively controlled through conventional rolling and annealing routes, the Cube 001//ND fiber, particularly the Rotated Cube 001110 component, remains poorly understood and rarely exploited, despite its potential benefits for soft magnetic applications. This manuscript reviews and rationalizes the formation and evolution of the Rotated Cube texture obtained through conventional sheet processing, encompassing phase transformation, cold rolling, and recrystallization annealing. Experimental observations demonstrate that the Rotated Cube component is continuously present, albeit with comparatively low intensities, because (extra/ultra) low-carbon steels have historically been optimized to suppress its development. The evolution of the Rotated Cube texture cannot be explained solely by classical orientation stability or high stored energy recrystallization arguments. Instead, evidence points to the decisive role of variant selection during the γ → α transformation, grain fragmentation during plastic deformation, and orientation selection during sub-grain growth, controlled by local misorientation gradients, in the early stages of recrystallization annealing. The manuscript further evaluates the capabilities and limitations of mean-field and full-field computational approaches for texture prediction, highlighting recent advances that incorporate microstructural heterogeneity into recrystallization modeling. By integrating experimental findings with physically based models, this work clarifies the multiscale mechanisms underlying Rotated Cube texture formation and outlines pathways toward its intentional control in low-carbon steels processed via conventional routes.

Liquid metal embrittlement (LME) during resistance spot welding (RSW) of twinning induced plasticity (TWIP) steel is primarily driven by stress-assisted grain boundary (GB) diffusion of zinc (Zn). Although GB diffusion is widely recognized as the dominant LME mechanism, experimental quantification is challenging due to resolution limitations. This study characterizes Zn diffusion in TWIP steel during RSW by conducting energy dispersive X-ray spectroscopy (EDS) line scans ahead of LME cracks in both the rolling direction (RD) and normal direction (ND) over weld times from 700 to 1700 ms. Results reveal that Zn diffusion distance increases with weld time, with consistently higher diffusion in the ND. To compare experimental measurements with diffusion theory, an FEA simulation based on Fick’s law was employed to approximate bulk Zn diffusion under varying temperatures. The model predicts Zn diffusion trends consistent with experimental observations. Although the diffusion distance predicted in the simulation exceeds measured values, directional trends are accurately captured. A theoretical framework to compare GB and bulk diffusion was proposed. GB diffusion distance of Zn is estimated to be approximately 30 times greater than bulk diffusion, establishing a quantitative link between weld time and Zn diffusion during RSW of TWIP steel.

Understanding the hot deformation behavior of metallic components produced via additive manufacturing (AM) is crucial, especially for applications in dynamic loads and high temperatures. This research examines the hot compression behavior of a martensitic precipitated hardened stainless steel, known as CX SS, produced through laser powder bed fusion (LPBF). Microstructural evolutions were examined on two sample types—as-built and heat-treated—subjected to hot compression at a constant 1 s⁻¹ strain rate within the temperature range of 300 °C to 650 °C. The impact of microstructural features such as cellular solidification subgrains, nanoscale NiAl precipitates, and the austenite reversion transformation on dynamic recovery (DRV) and dynamic recrystallization (DRX) as mechanisms of restoration is explored using electron backscattered diffraction (EBSD) techniques. A comparison between two sample types revealed that the presence of cellular solidification substructure in the as-built samples delays the restoration mechanism compared to heat-treated samples. Furthermore, LPBF CX specimens in the as-built state and after heat-treatment process exhibit nearly identical deformation behavior at temperatures above 450 °C. This identical deformation behavior is associated with the partial or complete destruction of cells in the as-built samples and the dissolution of NiAl particles in heat-treated ones. The dynamic softening mechanism primarily stems from DRV and partial DRX. Although discontinuous dynamic recrystallization (DDRX) was alleviated in heat-treated samples, the as-built CX SS also showed softening mechanism in form of continuous dynamic recrystallization (CDRX) accompanied by DDRX. A constitutive equation of Arrhenius model, including Zener–Hollomon parameters, evaluated strain accumulation during hot deformation, identifying regions prone to shear bands (SBs), microcracks, and voids.

The combination of mechanical properties (strength, toughness, and crack arrestability) and weldability that is required of steel pipelines has led to the pipeline steel grades that are used today. The only way to control the mechanical properties of these grades is by controlling microstructure and crystallographic texture of the steel plates. In this chapter, descriptions are provided of the microstructure and texture in the most commonly used pipeline steel grades. The composition ranges of these grades are summarized, together with a brief discussion of segregation effects. After a short historical review, the general principles of microstructure and texture formation during the thermomechanically controlled processing of plate and sheet are discussed. These are illustrated with examples taken from the literature and the authors' research. Special attention is paid to texture formation, methods of texture control, and the influence of texture on mechanical properties, anisotropy, and fracture behavior of these microalloyed steels.

This work investigates the formation of the recrystallisation microstructure and texture of various single-phase ferrite low-carbon steels that were rolled at different temperatures and of which the deformation microstructure was characterized by high resolution electron backscatter diffraction (EBSD). Three cases are considered: (i) cold-rolled interstitial-free (IF) steel, warm-rolled IF steel at 550 °C and warm rolled Fe-Si steel at 900 °C (below the austenitization temperature due to Si). It is well-known that the deformation texture after flat rolling of single-ferrite low carbon steels exhibits the characteristic α/γ-fiber texture, i.e. <110>//Rolling Direction (RD) and <111>//Normal Direction (ND), irrespective of the rolling temperature, as long as there is no concurrent phase transformation. However, different recrystallisation textures appear as a function of the rolling temperature. Generally speaking, the γ-fiber recrystallisation texture is obtained after cold rolling, whereas the θ-fiber components ( <100>//ND) intensify at the expense of the γ-fiber orientations with increasing rolling temperature. Although these phenomena are well-known, the reasons for this behavior in terms of preferential orientation selection remain as yet unclear. In the present paper, recrystallisation microstructures and textures are simulated with a full-field cellular-automaton (CA) description, whereby recrystallisation from its incipient stage is considered as a process of sub-grain coarsening controlled by the well-known physical laws of driving force and kinetics. The simulations integrate in one single model the various conditions that give rise to the observed temperature dependence of the evolving static recrystallisation texture and microstructure. The different rolling temperatures will give rise to different initial microstructures at the onset of recrystallisation with noticeable variations in short-range orientation gradients in γ and θ-fiber orientations, respectively. The mere application of local grain-boundary migration laws on the topology of the deformation structure, without imposing any specific nucleation selection criterion, will properly balance the dominance of γ-fiber grains after cold-rolling and θ-fiber orientations after warm rolling. Finally, the well-known nucleation of Goss orientations ({110}<001>) in shear bands occurring in γ-fiber grains is also simulated in this single conceptual framework.

The accuracy of simulated recrystallisation textures is essential for predicting the formability of steel sheets. In a continuum modelling approach, this texture can be effectively calculated in two stages: nucleation and growth. However, the precision of the final texture depends heavily on the accuracy of the nucleation texture simulation. This paper presents a nucleation texture model that combines the strain-induced boundary migration (SIBM) mechanism with a traditional oriented nucleation model. The results indicate that the SIBM mechanism promotes the nucleation of low-stored energy grains and enhances the nucleation texture compared to using the oriented nucleation model alone. The findings suggest that the accuracy of nucleation texture could be improved by setting a minimum stored energy threshold for grains that nucleate during the early stages of recrystallisation.

Despite the widespread use of laser heat treatment, a fundamental understanding of austenite formation kinetics at high heating rates remains a challenge. This gap is addressed by developing a novel model that uniquely accounts for the initial pearlite colony size and interlamellar spacing as critical input parameters. The model's predictions are validated against experimental observations, where the spatial variation of hardness reveals a distinct two-zone microstructure: a fully austenitized region and a partially transformed intercritical layer. The results show that the relative size of these zones is directly controlled by the initial microstructure. This research provides a crucial insight that austenite formation under rapid heating conditions occurs with negligible superheating, which is essential for optimizing laser processing parameters to achieve a desired microstructure.

A systematic experimental study has been carried out to understand ferrite recrystallization during isothermal annealing just below Ac1 in dual phase steels. Three different dual phase microstructures – ferrite-pearlite (FP), ferrite-bainite (FB) and ferrite-martensite (FM) were produced with an identical chemical composition. These samples were subjected to 80 % cold work and subsequently annealed at 725 °C for different soaking durations. The complex interaction between ferrite and secondary constituent/phase during deformation lead to differences in strain partitioning which influenced the kinetics of ferrite recrystallization. The sample with ferrite-martensite (FM) microstructure exhibited faster recrystallization kinetics followed by ferrite-bainite (FB) and ferrite-pearlite (FP). The microstructure and associated hardness evolution starting from cold rolling to annealing for different durations was carefully captured with electron back scattered diffraction (EBSD) and high-speed nanoindentation mapping. Excellent one-to-one correlation between hardness and KAM was observed by coupling EBSD-KAM and nanoindentation mapping. The effect of the secondary constituent/phase on ferrite recrystallization is presented and differences in the recrystallization kinetics are reconciled by correlative characterization. This work lays a foundation to link microstructure to the local mechanical response in dual phase steels and can be gainfully used to characterize multiphase steels and ultimately fine tune the processing.

Electrical steels, also known as silicon steels, play an essential role in the generation, transmission, and use of electricity. The magnetic quality of electrical steels and thus the energy efficiency of electromagnetic devices are highly dependent on the thermomechanical processing procedures employed to manufacture the electrical steel sheets. Every processing step, from casting, hot rolling, cold rolling to annealing, introduces a specific microstructure and texture, which influences the microstructure and texture of next processing steps as well as the final magnetic properties. In this paper, both types of electrical steel, i.e., grain-oriented electrical steel (GOES) and non-oriented electrical steel (NOES), are reviewed bearing in mind that NOES has perhaps received less attention till now. The magnetism of ferromagnetic materials and the metallurgical factors that affect the magnetic properties of electrical steels are first briefly discussed. The effect of each thermomechanical processing step on the formation of the microstructure and texture of the final electrical steel sheets is then scrutinised. The status and challenges in optimising the crystallographic texture of electrical steels are discussed. Future directions to the development of energy-efficient and cost-effective electrical steels are pointed out.

Wire arc additive manufacturing (WAAM) is a significant area of interest within the field of additive manufacturing (AM). In the present research, WAAM technology was employed to deposit a Ni-based alloy on a ductile cast iron substrate to fabricate a bimetallic structure of Ni-45 %Fe alloy and ductile cast iron. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron back scattered diffraction (EBSD) and X-ray diffraction (XRD) were used to study phase transformations, microstructure and crystallographic texture development in interfacial regions as well as deposited material. The mechanical properties were also studied using micro-hardness and profilometry-based indentation plastometry (PIP) measurements. The results showed that a wide variety of phases are generated within the heat-affected zone (HAZ) and partially melted zone (PMZ). These phases form complex microstructures with single and double shell morphology. The deposited alloy has a face-centred cubic (FCC) structure, with some carbides and graphite that are formed during the solidification of the first deposited layer. The compositional changes were also observed across the interface. The texture of the deposited alloy showed around 30° deviation from 〈100〉 II building direction due to the shape and overlap of the melt pools. The present results provide a better understanding of interface development mechanisms during WAAM of bimetallic structures. The peak of the hardness across the interface was observed in PMZ because of the formation of a martensitic matrix. The PIP measurements showed that the σ_y and the UTS of deposited alloy are lower than the cast iron base metal.

This study investigates the subsequent stages of recrystallisation in Interstitial-Free (IF) steel subjected to an unconventional continuous annealing process with a controlled thermal gradient. A cold-rolled steel strip was exposed to varying annealing temperatures along its length, enabling the analysis of microstructural evolution during the course of recrystallisation. The microstructure and stored energy were assessed at various positions along the strip using Electron Backscatter Diffraction (EBSD). The results underscore the significant influence of local misorientation and structural inhomogeneity on orientation selection during recrystallisation. The remaining non-recrystallised volume fraction (NRF) strongly correlates with the average misorientation gradient, obeying a phenomenological power-law correspondence with an exponent of ~3.7. This indicates that the recrystallisation process is highly sensitive to small changes in local orientation gradients. These findings highlight the crucial role of stored energy distribution for texture evolution, particularly during the early stages of recrystallisation in continuous annealing. It is observed that g-fiber grains, in comparison to a-fiber grains, are much more susceptible to grain fragmentation and therefore develop more robust intra-granular misorientation gradients, allowing for successful nucleation events to occur. In the present study, these phenomena are documented in a statistically representative manner. These insights are valuable for optimising thermal processing in interstitial-free (IF) steels.

Wire Arc Additive Manufacturing (WAAM) is a metal Additive Manufacturing (AM) technique that can produce fully dense metallic structures with virtually no porosity and at high productivity, compared to other currently available AM techniques such as Laser Powder Bed Fusion (L-PBF). As development of the technique is still ongoing, monitoring or post-fabrication inspection methods are under active investigation. In this work, we apply Resonant Ultrasound Spectroscopy (RUS) to samples fabricated from two different wires (construction steel and austenitic stainless steel) and quantitatively characterize isotropic and anisotropic elastic behaviour of the obtained dense parts. We find that an isotropic elastic model fits the construction steel samples well. For the 316 L polycrystal however, the isotropic elastic model is unsatisfactory, and an effective orthotropic elastic model is found to fit the resonance data. EBSD and XRD measurements are used to confirm and explain this difference in elastic behaviour between steel grades by the presence of a strong texture in the 316 L samples. Additionally, the texture data measured by EBSD are used to infer single crystal constants from the polycrystal resonance data using the Hill averaging scheme for one of the 316 L samples. We end by discussing the differences between the two elastic models used in the study (orthotropic and texture based) as well as the link between the measured resonances and microstructural descriptions of the samples.

The current study investigates the microscale mechanical properties of the constituent phases and their influence on the macroscale properties of multi-phase steels with different microstructural constituents. Two steels, a Transformation Induced Plasticity (TRIP) and an enhanced ductility Dual Phase (DH) steel were produced in a continuous annealing line (CAL). Optical microscopy and EBSD results were utilized for segmentation of microstructural phase constituents. Macroscale mechanical properties were obtained using tensile testing and microscale properties with nanoindentation mapping. The hardness of each constituent is extracted from the hardness maps using a clustering algorithm. TRIP steel shows a homogeneous distribution of retained austenite in ferrite matrix and a small amount of bainite/martensite which is non-banded. In contrast, DH steel shows heterogeneous microstructures where martensite/bainite/retained austenite is found to be banded in the ferrite matrix. Both steels exhibit notable variations in hardness across their constituent phases, which are associated with the resulting microstructural characteristics. Nanoindentation results show that overall hardness/strength in TRIP steel is contributed from ferrite (66 %), retained austenite (33 %) and martensite/bainite (1 %). Whereas in DH steel, it is contributed from ferrite (55 %), mixture of RA, martensite/bainite (∼40 %) and martensite (∼5 %). The macroscopic behavior of TRIP and DH steels was explained and discussed using the rule of mixtures in conjunction with the microscopic properties of individual phases.

In the present study, the crystallography aspects of the liquid metal embrittlement (LME) phenomenon are investigated in a bi-metallic bronze-stainless steel structure, produced using wire arc additive manufacturing. Most of the LME cracks were found to be propagated along high-angle grain boundaries of the austenitic structure. Surprisingly, it was observed that in some cases, LME cracks propagated transgranularly in austenite grains, which is a rare phenomenon in LME of steels. The Ʃ3-coincidence site lattice (CLS) boundaries showed the highest resistance to LME compared to other CLS types. It was also found that the presence of elongated grains in additively manufactured microstructures can accelerate the LME phenomenon.

This study explores the evolution of solidification microstructure of a laser powder bed fusion (L-PBF) martensitic stainless steel during solution annealing and aging. Quasi in-situ experiments using electron backscatter diffraction (EBSD) revealed that the finer, more equiaxed microstructure below the melt pool was susceptible to recrystallization and grain growth during solution annealing. The two distinct solidification microstructures below and inside the melt pool converged into a uniform grain morphology after solution annealing and aging processes. Graphical Abstract: (Figure presented.)