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Repair offers significant time—cost savings and durability by reusing existing parts efficiently. Prior to implementation of repaired parts, it is crucial to clarify mechanical properties and deformation mechanisms to ensure proper performance. In this study, a repair deposition was performed on the groove of wrought stainless steel 316L using the same material powder. The repaired sample exhibited an excellent combination of ductility and strength (T.EL: 58%, YS: 407 MPa, UTS: 673 MPa) compared to the wrought counterpart. With heterogeneity in microstructure, the hetero-deformation-induced strengthening of the repaired sample resulted in a synergy of strength-ductility combinations.

This study delves into effects of deep cryogenic treatment (DCT) on enhancing the hydrogen embrittlement resistance of CoCrFeMnNi high-entropy alloy fabricated via laser powder-bed-fusion (L-PBF). Comparatively assessing as-print, conventional heat treatment, and DCT, we uncover how nanotwin formation within matrix serves as a critical mechanism to combat adverse effects of hydrogen embrittlement. This work reveals that DCT not only mitigates inherent residual stresses from L-PBF, thereby fostering dislocation redistribution and microstructural stabilization, but also synergizes with high-density dislocation cells. Our findings articulate a nuanced understanding of microstructural evolution in response to post-treatments and consequential enhancement of hydrogen embrittlement resistance.Highlights Laser-based additively manufactured CoCrFeMnNi undergoes post heat treatment and deep cryogenic treatment to tailor dislocations and residual stress.The inherent residual stress acts as the driving force for the redistribution of dislocations, leading to the development of a stable microstructure after deep cryogenic treatment.High-density dislocation cells and hydrogen collaborate to lower the local stacking fault energy, triggering gradient nanotwins.Nanotwin-ability effects by deep cryogenic treatment (77 K × 36 h) on the hydrogen embrittlement resistance of CoCrFeMnNi with interior defects are verified.

Direct energy deposition (DED) has gained attention in the field of metal repair because of its ability to integrate additively deposited material with preexisting components. Having the beneficial aspects of depositing right material, DED is evaluated the best option for repair deposition. Machining grooves in damaged components is the common first to repair, which is necessary to remove cracked or damaged material and provide suitable geometry for deposition. Preprocessing as grooving is commonly applied to prevent the propagation cracks or tears. However, challenges such as dimensional error and crack induced by residual stress emerge owning to complex interactions between the DED parameters and groove geometry during repair deposition. This study investigates effective deposition strategies for repairing 316L stainless steel grooves with wall-angles of 90° and 135° by exploring the relationship between the repair integrity and parameters such as groove angles, laser energy input, and powder supply, all with reference to the underlying mechanism of metallurgical bonding in angled areas. Based thereon, a modified effective repair strategy is proposed, using enhanced dual laser power to address bonding issues in the angled areas. Samples repaired using this method exhibit a defect-free groove–deposit interface and a continuous columnar-grained microstructure with abrupt changes in grain size between the repaired area and groove. This microstructural heterogeneity results in an exceptional combination of strength and ductility when compared to the base material and samples repaired using a single laser strategy. The findings of this study provide insights into the optimization of DED strategies for achieving robust metallurgical bonding within grooves, thereby advancing technological maturity in the field of metal repair.

Crack-free Al–Zn–Mg–Cu alloy, processed by laser powder bed fusion, displays a characteristic microstructure comprising fine equiaxed grains (EGs) and coarse columnar grains (CGs). Notably, the CGs show a high hardness compared to EGs due to the high density of in-situ precipitates. Analysis of mechanical properties takes into account the precipitates in the grain and hierarchical differences in grain morphologies near the melt pool boundary. Strengthening mechanisms are elucidated through synergistic hetero-deformation-induced strengthening, where multi-modal-sized EGs induce significant strain gradients within EG regions. Our findings demonstrate the potential to enhance strength of Al–Zn–Mg–Cu-based alloy in as-built state through architecting microstructures.

This study explores cellular structures in TiC/B4CCoCrFeMnNi high-entropy composites (HECs) fabricated by direct energy deposition (DED) additive manufacturing process, investigating the role of TiC and B4C nano-paticles in enhancing mechanical properties. Despite larger dislocation cell structures and thinner boundaries in TiC/B4CCoCrFeMnNi HECs compared to CoCrFeMnNi high-entropy alloy (HEA), they exhibit significantly higher hardness and strength, challenging traditional strength-size relationships. Additionally, we examine the behavior of ceramic nano-particles (TiC and B4C) with high melting points relative to matrix CoCrFeMnNi HEA. Rapid scanning prevents full nano-particle melting, leading to distinct element distribution of cell structure. These findings provide insights for selecting suitable nanoceramic particles in HEC development via metal additive manufacturing.

The configurational design of heterostructures has received considerable attention to achieve a superior combination of strength and ductility. Although heterostructuring for enhanced tensile properties has been widely analyzed, studies on the effect of heterogeneity on sheet formability are still insufficient. Sheet metal formability is one of the most crucial factors for determining hetero-materials’ industrial utilization. To broaden the industrial applicability of heterostructured layered materials, investigating the effects of heterogeneity in the layered structure on formability is necessary. This study investigated the stretch formability of aluminum-steel-aluminum clad sheets using the Erichsen cupping test. The three-layered clad sheets showed additional hardening with a slight increase in ductility owing to hetero-deformation-induced hardening because the strain-hardening exponent has a linear relationship with stretchability or necking resistance. After necking, damage evolution owing to severe internal stress concentration led to delamination at the interface. Interestingly, delamination serves as a block to full cracking through the thickness during forming. This study contributes to the industrial applicability of heterogeneous structuring by elucidating the characteristics of heterogeneity and formability.

Macroscopic and microscopic mechanical properties, and damage behaviors of materials should be evaluated through multi-scale investigations to allow for practical industrial applications and promote user safety. Clad metal, a type of heterostructured material, is one of the most promising advanced materials for commercialization. However, heterostructured materials (e.g., clad metals, multi-phase metals, and composite metals) are limited by the possible deterioration of their mechanical properties caused by the strain partitioning at the interface of dissimilar phases when heavily deformed. Therefore, quantitative analysis of multi-scale damage development is necessary for the beneficial future utilization of clad metals as well as structural materials that are currently used in the industry. In this study, the mechanical properties and damage behaviors of Al1050/low-carbon steel/Al1050 clad sheet at multiple scales were quantitatively analyzed using macro-scale digital image correlation (DIC) and micro-scale DIC techniques. The multi-scale investigation results will contribute to the improvement of the reliability of clad materials by quantitatively identifying their mechanical properties and damage behaviors on various scales, which will be beneficial for industrial applications.

We propose a method for obtaining reliable wide strain range equivalent stress–strain curves from tensile testing by applying 3D digital image correlation. Herein, both the front and side surfaces of the specimen were identified by the 45° tilting of the specimens. The deformation of the specimen was the most severe in the neck section, and the equivalent strain representing the entire specimen could be extracted from the neck regions on the side and front surfaces. In addition, the equivalent stress was obtained by calculating the reduction in the varying cross-sectional area from the strain information of the two surfaces. The resulting wide strain range equivalent stress–strain curves can describe nonlinear hardening behaviors up to higher strains than the conventional gauge length method. The proposed method can provide wide strain range equivalent stress–strain curves only through experiments without requiring separate finite element method simulations or correction factors.