Metals and Materials International最新文献

Corrosion of joints at high temperatures is a major challenge in industrial applications. This study examines the effect of interlayer thickness (38, 76, and 100 µm) on the hot corrosion behavior of Hastelloy X superalloy joints bonded via transient liquid phase bonding in a Na₂SO₄–V₂O₅ eutectic at 900 °C. It is hypothesized that a thinner interlayer improves corrosion resistance by forming a stable oxide layer. To validate this, corrosion products, microstructural evolution, and elemental composition were analyzed using X-ray diffraction, optical microscopy, field emission scanning electron microscopy, and energy-dispersive spectroscopy. Results show that the 38 µm interlayer enhances resistance due to the formation of a protective Cr₂O₃, NiCr₂O₄, and NiO oxide layer. In contrast, increasing the thickness to 100 µm intensifies elemental diffusion, leading to a higher concentration of boride and silicide compounds in the diffusion affected zone, reducing corrosion resistance. Initially, corrosion forms a dense Cr₂O₃–NiO oxide layer. However, after 20 h, vanadium (V) reacts with the alloy, forming NaVO₃, while sulfur (S) infiltration leads to Ni, Cr, and Mo-based sulfides, promoting intergranular corrosion. The formation of NaVO₃ and SO₃, along with Cr₂O₃ depletion, further accelerates degradation over time.

Graphical Abstract

Significant work has been done on the analysis of microstructure and texture in Ti6Al4V parts with simple geometric shapes like cubes or cylinders manufactured using laser powder bed fusion (LPBF). However, in recent times, there has been considerable interest in the use of triply periodic minimum surfaces (TPMS) in additive manufacturing (AM) in the production of titanium-based lattices for hard tissue applications. The present work utilizes a diamond TPMS lattice-based tensile specimen to explore the geometry-dependent variation in microstructure and preferred crystallographic orientations in relation to the observed tensile behaviour. Three regions within a single tensile specimen namely lattice region (LR), lattice-solid junction region (L-SR) and solid region (SR) were studied. The results indicated a change in the aspect ratio of the martensitic lath from ~ 5 in the LR to 3.8 in the SR within an individual as-built specimen. Moreover, the texture strength was considerably higher in LR as compared to SR. The texture for the as-built LR was noted to be arrested in progression to form a < 0001 >|| build direction (B.D) crystallographic orientation. The underdeveloped texture in the LR was completed to form a < 0001 >||B.D preferred orientation and was further intensified by the heat treatment (HT) done at 750 °C for 4 h and 920 °C for 2 h followed by furnace cooling. An improvement in the ductility was observed for both the HT processes and is mainly attributed to the coarsening of grains and β-phase with negligible impact of the texture within the LR on the ductility of the specimens.

Graphic Abstract

Aluminum alloys are the first choice for the preparation of integrated structure–function materials, but the conflicting relationship between mechanical properties and thermal conductivity limits the application of aluminum alloys. This study takes Al–6Si–0.6Mg–0.1Sc alloy as the subject of research. It adopts the semi-solid rheological die-casting process, combines composite modification and heat treatment methods to prepare aluminum alloy materials with high strength and high thermal conductivity. Meanwhile, X-ray, OM, SEM, TEM, XRD, tensile test and thermal conductivity test were used to study the changes in the microstructure and properties, and to reveal its strengthening and thermal conductivity mechanism. The results show that the composite addition of Sr/Ca can effectively improve the morphology of Al–Si eutectic phase and Mg₂Si phase in Al–6Si–0.6Mg–0.1Sc alloy, which changes the Al–Si eutectic phase from its original lamellar shape into fine granular particles, increasing the electron channels and mean free paths. As a result, the mechanical properties and thermal conductivity of the alloy are enhanced. After the semi-solid die-cast Al–6Si–0.6Mg–0.1Sc alloy undergoes T6 heat treatment (470 °C × 4 h + 180 °C × 12 h), the improvement of the microstructure morphology and the distortion of the internal lattice lead to the simultaneous enhancement of both the mechanical properties and the thermal conductivity of the alloy. The tensile strength, yield strength and elongation of the alloy in the T6 state reach 327 MPa, 196 MPa and 6.5%, respectively, and the thermal conductivity reaches 156.1 W/m K. The tensile strength and thermal conductivity of the alloy are 16% and 13.2% higher than those of the semi-solid die casting, respectively.

Graphic Abstract

The effects of solute on the generalized stacking fault energy of basal plane, prismatic plane and pyramidal slip systems in Mg-X binary magnesium alloy have been systematically studied by using first-principles density functional theory (DFT). The addition of elements having low elastic modulus, larger original size and lower first ionization energy is considered to improve the plasticity of magnesium alloy. Starting from the formation process of dislocation, the synergistic effect and comprehensive effect of alloying elements on multiple slip systems are established. Based on the weight of the slip system, the stacking fault energy distribution diagram of GSFE weight model is established, and good consistency is obtained between the results of those of GSFE weight model and DFT. At the same time, the activation probability result show that < a > the activation probability of basal plane dislocations is more than twice that of pyramidal plane dislocations. It accords with the preferential activation of basal slip system at room temperature < a > . The plasticity of magnesium alloy can be improved remarkably by activating pyramidal type II < c + a > dislocations. The ductility of alloys can be assessed qualitatively in terms of pyramidal slip systems.

Graphical Abstract

Ti/Al clad plates combine several beneficial properties, including low cost, light weight, and high strength. However, these materials encounter issues, such as poor deformation compatibility and high susceptibility to oxidation, leading to weak interfacial bonding. In this study, multilayer Ti/Al clad plates were fabricated via vacuum rolling, producing oxidation-free and clean interfaces. The symmetric billet design facilitated the coordination of the Ti and Al deformation, which resulted in an ideal structure. The diffusion layers of Ti and Al were observed at the rolled Ti/Al composite interface, while there was no obvious diffusion of Si and no formation of Al₃Ti. The Ti/Al clad plate after rolling exhibited an ultimate tensile strength (UTS) of ~ 290 MPa and an elongation of ~ 13.6%. After 3 h of annealing, fine Al₃Ti particles were detected at the interface. After 6 h of annealing, a continuous and dense Al₃Ti layer with a thickness of approximately 0.954 μm was formed, which significantly enhanced the tensile properties (UTS of ~ 323 MPa and elongation of ~ 22.8%). After 15 h of annealing, the Al₃Ti layer increased to ~ 3.5 μm, illustrating the effect of annealing time on interfacial layer growth. Meanwhile, the width of the interfacial Si diffusion zone also gradually increased with prolonged annealing. These findings highlight the importance of controlling the intermetallic layer thickness to achieve an optimal balance between UTS and elongation in Ti/Al clad plates.

Graphical Abstract

This study adopts a stabilization treatment agent of CuSO₄, FeSO₄, NaHSO₃, NaCl, and CaCl₂ solution systems to stabilize the treatment of Q420qNH weathering steel (WS) surfaces. Comparative analysis was conducted between WS with (sample A) and without (sample B) stabilization treatment. The investigation included dry/wet cyclic corrosion tests, electrochemical techniques, morphological characterizations, and component analyses. The findings indicate that sample A exhibits greater corrosion weight gain and rust layer thickness than sample B. The rust layer of sample A, characterized by higher density and flatness, predominantly consists of Fe₃O₄, γ-Fe₂O₃, α-FeOOH, γ-FeOOH, β-FeOOH, and CaSO₄ phases. CaSO₄ notably contributes to filling the defect in the rust layer, thereby improving the structure of the initial layer. After 64 cycles of the corrosion test, sample A’s rust layer appeared uniform and continuous, with a 27% α-FeOOH content (a 7% improvement) and a self-corrosion potential (E_corr) of -0.681 V, an improvement of 120 mV. Surface stabilization treatment was observed to promote the enrichment of alloying elements such as Cu and Cr in the rust layer’s cracks, thus accelerating the formation of a dense, stable rust layer and substantially enhancing the corrosion resistance of rust layer on Q420qNH WS surface.

In this work, the high-pressure torsion (HPT) technique is used to fabricate bulk metallic glass and composite samples of magnesium-rich Mg₇₂Ca₁₂Zn₁₆ and Mg₇₂Ca₁₂Zn₁₄Sn₂ alloys. Mg₇₂Ca₁₂Zn₁₄Sn₂ is a new glass-forming alloy, and its glass-forming ability is slightly lower than that of the Mg₇₂Ca₁₂Zn₁₆ alloy. Amorphous and composite ribbons of both alloys were subjected to HPT processing with 25, 50, and 70 turns separately to prepare bulk samples. For the amorphous samples, a homogeneous microstructure is achieved throughout the sample after 50 turns, and for the composite samples, microstructure homogenization is achieved after 70 turns. After the entire HPT process, no strain-induced crystallization was detected in both amorphous and composite samples. This study indicates that Mg-based metallic glasses and composites can be fabricated into bulk components even with low glass-forming ability. The microstructural refinement leads to a higher hardness than the starting material.

The effect of pre-peak-aging prior to hot-extrusion on the microstructure, the deformation mode and mechanical properties of Mg-Gd-Y-Zn-Zr alloy are investigated. Pre-peak-aging treatment induces dynamic precipitation of β particles during hot-extrusion, β particles not only promote recrystallization nucleation through the particle stimulated nucleation (PSN) effect, but also generate significant pinning effect on recrystallized grains, which further regulates the inhomogeneous plastic deformation and bimodal microstructure. H-530PA sample (homogenization + pre-peak-aging) exhibits excellent mechanical properties, with tensile strength, yield strength, and elongation of 403, 328 MPa, and 9.0%, respectively, which is related to the texture strengthening, dislocation strengthening, heterogeneous deformation induced strengthening caused by the modulated bimodal microstructure and Orowan strengthening by β particles, and the increased recrystallization fraction also enhances plasticity. The deformation mode of the recrystallized regions is grain boundary sliding, while the unrecrystallized regions are dominated by non-basal slip, the strain incompatibility between the two is the decisive factor causing microcracks propagation and final fracture.

Graphical Abstract

Conventional cemented carbide materials typically use metallic binders during sintering, compromising performance under high-temperature conditions due to binder deformation, reducing hardness and wear resistance. This study addresses these limitations by developing binderless tungsten carbide (WC) compacts that eliminate metallic binders, maximising the intrinsic properties of pure WC and enhancing high-temperature stability. However, binderless WC compacts require sintering above 1900 °C, which promotes excessive grain growth and compromises mechanical properties. To overcome these challenges, 100 nm WC powders were vacuum sintered at temperatures below 1700 °C, with vanadium carbide (VC) added as a grain growth inhibitor to suppress grain coarsening. Although the addition controlled the grain growth, it also hindered densification, which was resolved by employing hot isostatic pressing (HIP) as a secondary process. This approach achieved high densification and eliminated residual pores, enabling the production of fine-grained, dense WC compacts. WC–VC mixed powders were vacuum-sintered at 1620–1700 °C; they then underwent HIP at 1650 °C under 150 MPa. The microstructure and mechanical properties were analysed for varying VC contents (0, 1, and 3 wt%). The WC–3VC compact sintered at 1650 °C achieved a relative density of 97% and Vickers hardness of 2725 Hv. These results demonstrate that controlling grain size and optimising densification significantly enhance the mechanical properties of binderless WC compacts, offering valuable insights for high-performance cemented carbide applications.

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