The repetitive corrugation and straightening process is a severe plastic deformation technique that is particularly suited to process metallic sheets. With this technique, it is possible to develop nano/ultrafine-grained structured materials, and therefore, to improve some mechanical properties such as the yield strength, ultimate tensile strength, and fatigue lifetime. In this study, an Al-6061 alloy was subjected to the repetitive corrugation and straightening process. A new corrugation die design was proposed in order to promote a heterogeneous deformation into the metallic sheet. The evolution of the mechanical properties and microstructure obtained by electron backscatter diffraction of the alloy showed a heterogeneous distribution in the grain size at the initial cycles of the repetitive corrugation and straightening process. Uniaxial tensile tests showed a significant increase in yield strength as the number of repetitive corrugation and straightening passes increased. The distribution of the plastic deformation was correlated with the hardness distribution on the surface. The hardness distribution map matched well with the heterogeneous distribution of the plastic deformation obtained by finite element simulation. A maximum average hardness (147 HV) and yield strength (385 MPa) was obtained for two repetitive corrugation and straightening cycles sample.

Sheets of 5754-aluminum alloy processed by a modified repetitive corrugation and straightening (RCS) process were tested in order to measure their formability. For this purpose, forming limit curves were derived. They showed that the material forming capacity decreased after being processed by RCS. However, they kept good formability in the initial stages of the RCS process. The formability study was complemented with microstructural analysis (derivation of texture) and mechanical tests to obtain the strain-rate sensitivity. The texture analysis was done by employing X-ray diffraction, obtaining pole figures, and the orientation distribution function. It was noticed that the initial texture was conserved after successive RCS passes, but the intensity dropped. RCS process did not induce β-fiber, contrary to common deformation process. The strain-rate sensitivity coefficient was measured through tensile tests at different temperatures and strain rates; the coefficient of the samples processed after one and two passes were still relatively high, indicating the capacity to delay necking, in agreement with the good formability observed in the initial passes of the RCS process.

Liquid metal embrittlement (LME) occurs when a normally ductile alloy undergoes brittle fracture in contact with a liquid metal. The mechanisms behind LME remain unclear, and most of the models rely on post mortem analyses. In this work, we overcome this limitation by performing in situ scanning electron microscopy (SEM) notched micro-bending tests on α-brasses exposed to the gallium–indium eutectic (EGaIn) at room temperature, enabling real-time correlation between load–displacement curves and crack evolution during LME. In the Cu-30%Zn alloy, LME was observed only after prior plastic deformation and ductile crack growth, confirming that liquid metal did not influence early plasticity. A two-step experiment further showed that a pre-existing crack in contact with EGaIn, under continued loading, was sufficient to trigger brittle fracture. The Cu-20%Zn alloy displayed alternating ductile and brittle events, with brittle cracks propagating horizontally before arresting in undeformed zones, leading to stepped load–displacement curves. By contrast, pure Cu and Cu-15%Zn showed only ductile fracture despite continuous contact with EGaIn. These results demonstrate that LME in the Cu-Zn/EGaIn system acts during crack propagation rather than initiation. The present in situ SEM methodology provides direct evidence of fracture mechanisms and a framework for future experimental modeling comparisons.

Controlling nanoscale heterogeneity in metallic glasses offers a promising route to tailor their mechanical behavior. In this work, we investigate (Zr34Cu66)100-xFex thin film metallic glasses (TFMGs) across a wide compositional range (x = 0 – 76 at.%) to reveal how immiscibility between Cu and Fe can lead to heterogeneity, thereby influencing their structure and mechanical properties. Guided by thermodynamic modeling, we show that (Zr34Cu66)100-xFex retains an amorphous structure up to 77.5 at.% Fe, enabling systematic investigation of a wide range of compositions within ZrCu-rich and Fe-rich regions. Ab initio molecular dynamics simulations reveal that Fe addition in the range of 17-29 at.% maximizes the population of highly stable icosahedral motifs, thereby increasing hardness (H) from ~ 7.9 up to ~ 8.5 GPa, while further Fe increase leads to a reduction in H as a result of the weakening of atomic bonds. At 76 at.% Fe, atom probe tomography reveals the presence of Cu-rich amorphous clusters, accompanied by H decrement down to ~ 7.6 GPa. Moreover, we show that nanoscale phase separation in the form of Cu-rich clusters controls the deformation mode, affecting the amplitude of strain rate serrations during nanoindentation, decreasing from ~ 16 down to ~ 5 for high Fe content, indicating a transition from localized to more homogeneous plastic flow. Overall, we demonstrate a simple approach to tailor local heterogeneities of TFMGs by introducing immiscible elemental constituents, successfully managing to control the mechanical behavior, which can be beneficial for advanced material applications.

Mécanismes de fragilisation d'alliages Cu-Zn par l'eutectique Ga-In: Ce travail présente l'étude de la sensibilité à la fragilisation par les métaux liquides (FML) à température ambiante de laitons alpha contenant différents taux de zinc par l'eutectique liquide In-Ga (EGaIn). Le liquide EGaIn mouille le cuivre pur de manière partielle avec un angle de contact relativement faible de 49 ± 5 °. Cet angle est plus faible pour les laitons alpha et décroit avec le pourcentage en zinc. Il est de 36 ± 5 ° pour le laiton Cu-30%Zn. De plus, l'intermétallique CuGa2 se forme dès le contact avec le liquide EGaIn avec le cuivre et les laitons alpha, indépendamment de la teneur en zinc. Les essais de flexion 3 points montrent que la sensibilité à la FML par l'EGaIn augmente pour des vitesses de déformation élevées, des taux de zinc plus élévés et des duretés plus importantes. Dans les cas de FML, le liquide EGaIn n'affecte pas la phase d'initiation de la fissure mais seulement la propagation de la fissuration. En effet, les faciès de rupture présentent toujours une initiation ductile de la fissure puis une rupture fragile. L'intermétallique CuGa2 empêche l'initiation d'une rupture fragile en limitant le contact entre le métal liquide et le laiton dans les premières phases de l'essai mécanique. Puis l'intermétallique se fissure et ainsi, le liquide EGaIn rentre en contact avec le laiton rendant possible la FML à condition de déformations plastiques suffisamment importantes du laiton. A cause de l'initiation d'une rupture ductile, le laiton Cu-30%Zn ne présente pas de sensibilité à la FML lorsque il est testé par le small punch test (SPT) standard. Cependant l'utilisation d'échantillons de SPT pré-entaillés permet l'observation pour ce laiton de la FML en contact avec l'EGaIn liquide. De plus, du fait de l'initiation d'une rupture ductile, il est impossible à partir des résultats des essais de SPT et de flexion de déterminer une ténacité en présence de métal liquide. C'est pourquoi, des micro-essais de flexion avec observations in-situ et présence d'une couche fine protectrice de W ont été mis en oeuvre. Ils ont permis de déterminer en présence d'EGaIn liquide une ténacité de 1,57 ± 0.08 MPa m1/2 pour le laiton Cu-30%Zn.