This study investigates the effect of annealing temperature on the microstructure evolution and mechanical properties of as-cast Fe50Mn30Co10Cr10 metastable high-entropy alloy. The as-cast alloy exhibits a dual-phase microstructure consisting of γ-FCC austenite and ε-HCP martensite. After annealing at 500-600 °C, only limited microstructural variation is observed, which is attributed to the sluggish atomic diffusion and insufficient thermal activation for extensive phase transformation. In contrast, annealing at 700-800 °C promotes the reverse transformation from ε-HCP martensite to γ-FCC austenite, resulting in an FCC-enriched microstructure. Among the investigated conditions, the 800 °C-annealed alloy exhibits the best strength–ductility combination, with an ultimate tensile strength of 558 MPa and a uniform elongation of 48.7
Growing research interest in medium-entropy alloys (MEAs) has been driven by their favorable combination of strength, ductility, and structural stability. Recent studies have demonstrated that gradient annealing is an effective approach for tailoring microstructural evolution and optimizing the strength–ductility synergy in MEAs (Ref 1). In this study, a CoCrNi medium-entropy alloy was subjected to cryogenic rolling in liquid nitrogen to thickness reductions of 50 and 75
In situ submerged repair of marine structures is an effective technology to restore damaged surfaces without dismantling large components. This approach is important for reducing repair time and maintenance cost in offshore and ship structures. As an emerging repair method in traditional onshore environments, wire and arc directed energy deposition (WADED) has the advantage of producing efficient and continuous deposited layers. In this paper, the feasibility of in situ underwater wet WADED repair with flux-cored wire on E40 substrate was investigated. The characterization of macroscopic morphology, microstructure, defects and HV10 has been highlighted as an important factor in reliability research. Slag inclusion consisting of TiO2, Al2O3 and CaO was distributed at the narrow position, which together with the cold cracks caused severe metal deficiency and macroscopic discontinuities in underwater wet WADED. The deposition route design effectively improved the layer formation and reduced slag inclusion. Z-shaped sequential deposition with a 7 mm interval produced the best layer continuity and the least slag inclusion among the tested routes. The tempering effect between adjacent beads effectively reduced the microhardness of HAZ by 175-225 HV10. The longitudinal specimens exhibited a tensile strength of 366.36 MPa and an elongation of 12.90
The study investigated the influence of substituting Ti for Co in Co65−xCr35Tix (x = 5, 10, and 15 wt.
In the present work, the fatigue behavior of coarse-grained (CG) and surface mechanical rolling treated (CG-SMRT) 7075 aluminum alloy specimens was investigated under uniaxial fatigue tests conducted at room temperature across a range of stress ratios (R = − 1, 0.05, 0.1, 0.3, and 0.5). The results indicate that both CG and CG-SMRT specimens exhibit surface and internal failure modes under various R values. Under a single stress ratio (0.1 and − 1), when the CG specimens transition to internal failure, their fatigue data are distributed along the S‑N curves of the CG‑SMRT specimens, exhibiting a characteristic independent of the surface processing condition. Six mean stress models were employed to normalize the fatigue data obtained under different stress ratios. The results demonstrate that the Walker model effectively captures the regularity observed under individual stress ratios and exhibits a failure‑mode‑dependent multi‑stage nonlinear S‑N curve characteristic in the relationship between equivalent stress amplitude and fatigue life. Furthermore, the Walker model reveals that the fatigue life governed by internal failure is inherently independent of the surface processing condition, representing a universal feature prevalent across different stress ratios rather than a phenomenon confined to specific stress ratios. This finding establishes the Walker model as an appropriate mean stress correction framework for unified life prediction of high‑strength aluminum alloys under both conventional and very‑high‑cycle fatigue regimes.
