Journal of Materials Engineering and Performance最新文献

In this study, the effects of different levels of pre-deformation and cyclic straining amplitudes on the mechanical performance and microstructural characteristics of the 2024 aluminum alloy were explored. 2024 aluminum alloy samples were first solution-treated at 495 °C for 1 h and then subjected to pre-deformation in the range from 1 to 7% at room temperature, followed by cyclic straining. Combined mechanical deformation processes, i.e., pre-deformation and cyclic straining, enabled the control over cluster precipitation, dislocation configurations, and the spatial distribution of strain, enhancing both the strength and ductility of the aluminum alloy. This approach offers novel insight into the design of aluminum alloys with desired strength and ductility. The changes in dislocation configurations, microstructure, and the spatial distribution of strain under different pre-deformation levels and cyclic strain amplitudes were meticulously studied. The results indicate that subjecting the alloy to pre-deformation before cyclic straining improves the alloy’s strength and ductility. The strength enhancement is attributed to the synergistic effects of dislocation strengthening and cluster strengthening, while the improved ductility is attributed to dislocation loops and evenly distributed strain.

Solid oxide fuel cells (SOFCs) receive significant attention due to theirs high efficiency, environmental advantages, and fuel flexibility. The interconnect is a crucial part that connects each cell in the SOFC stack. The High Entropy Alloy (HEA) of FeCoCrNiMn_0.5 is a promising candidate for an interconnect material at intermediate temperatures (600 °C to 800 °C) in Solid Oxide Fuel Cells (SOFC) due to its good thermal stability and electrical conductivity. However, FeCoCrNiMn_0.5 HEA has a higher coefficient of thermal expansion (CTE) than the other interconnect materials (SUS 430, Crofer 22 APU) in SOFCs such as LSM (Lanthanum Strontium Manganite) cathode and NiO-YSZ anode. The high CTE in an HEA is undesirable as it mismatches with the CTE of cathodes and anodes in SOFC. The present study investigates the thermophysical properties and oxidation behavior of an Nb-contained HEA (Cr₂₁Co₂₁Fe₂₁Ni₂₁Mn₁₁Nb₅) to achieve reduced CTE and improved oxidation properties than the existing interconnect HEAs. The novel Cr₂₁Co₂₁Fe₂₁Ni₂₁Mn₁₁Nb₅ HEA was produced by the vacuum arc melting technique. The structure, chemical composition, mechanical properties, CTE, and thermal stability of the HEA were investigated. The oxidation study was also carried out by oxidizing the as-cast HEA at 800 °C for 25, 50, 100, and 200 hours. The study revealed that the presence of Nb reduces the CTE, increases oxidation resistance, and improves the mechanical properties of the HEA. The harmful Chromium oxide layer does not appear on the top of the thermally grown oxide layer during oxidation of the HEA. This passivation of the Chromium oxide layer will significantly reduce the Cr-poisoning in SOFC.

In this study, an ultrafine-grained 6061 alloy sheet was fabricated through cross accumulative roll bonding (CARB) and subsequent aging treatment. As the number of passes increases, the dislocation density rises, and the maximum density of the Brass {110}〈112〉 component also increases. Moreover, the grains are gradually refined. These phenomena are beneficial for enhancing the strength of the 6061 alloy sheet. After undergoing peak aging at 100 °C for 26 h, the tensile strength of the CARB specimen is further elevated to 464 MPa, accompanied by a slight decrease in elongation. The strength increment of the specimen aged at 100 °C can be attributed to the formation of nano-precipitated phases. In contrast, for specimens aged at higher temperatures, the significant decline in both strength and elongation is predominantly caused by the coarsening of the grain size. This clearly indicates that the aging temperature exerts a crucial influence on the mechanical properties of the CARB-processed 6061 alloy sheet, with the formation of nano-precipitates at lower temperatures enhancing strength and grain coarsening at higher temperatures deteriorating both strength and ductility.

This study explores the evolution of γ′ precipitates in a Co-10Al-5W superalloy when subjected to temperatures of 900, 950 and 1000 °C. The changes in shape, size and distribution of these precipitates were systematically analyzed using electron microscopy. Results indicate that the γ′ precipitates exhibit a cubic morphology and tend to coarsen progressively as temperature and aging duration increase. The coarsening kinetics were assessed through diffusion-based activation energy calculations, following the Lifshitz–Slyozov–Wagner theory. It was determined that the activation energy required for γ′ precipitate coarsening is 272 kJ mol⁻¹, and Al diffusion in the γ matrix plays a crucial role in this process. Additionally, the γ/γ′ interfacial energy at 1000 °C was found to be 86 mJ/m². These findings contribute to the advancement of Co-based superalloys by providing essential insights into their thermal stability and high-temperature performance optimization.

Al₂O₃-based ceramic composites are widely used as cutting tool materials owing to their high strength and oxidation resistance. However, their brittleness and low toughness can adversely affect their application and performance. Consequently, Al₂O₃/SiC composites with different Ti mass fractions (0, 0.5, 1, 5, and 10 wt.%) were prepared via vacuum hot-press sintering to optimize their strength and toughness. Their structural and mechanical properties were characterized using x-ray diffraction (XRD), relative density, hardness, flexural strength, fracture toughness, and fracture morphology. A high relative density for the Al₂O₃/SiC composites was achieved (> 95%) under 1400 °C and 40 MPa conditions, and the incorporation of Ti was confirmed by XRD. The hardness and flexural strength of the Ti-doped Al₂O₃/SiC composites increased with increasing Ti content, reaching a maximum at a Ti content of 5 wt.%, and then decreasing as the Ti content increased further. The maximum hardness and flexural strength values (at 5% Ti content) were 7.12 and 443 MPa, respectively. The findings of this study show that the addition of Ti generally improves the mechanical properties and provides toughening effects, providing data support for Ti-toughened Al₂O₃/SiC composite tools.

Ultra-high strength Mg-12.2Gd-2.2Y-1.2Zn-0.5Mn(wt.%) alloys were developed through hot extrusion, cold-rolling, and aging treatments. This study investigates the effects of rolling reductions (0, 3.0, 5.6, 9.6%) on the microstructure and mechanical properties of the Mg-Gd-Y-Zn-Mn alloys. Results revealed the presence of a bimodal-grained structure in the deformed alloys. Cold-rolling promoted grain refinement and increased the proportion of refined grain during subsequent aging. The ultimate tensile strength of the peak-aged alloys initially increased and then decreased with increasing rolling reductions. Following a 5.6% rolling reduction and aging treatment, the extruded Mg alloy exhibited excellent mechanical properties, achieving an ultra-high ultimate tensile strength of 571 MPa, a tensile yield strength of 493 MPa and an elongation to failure of 3.7%. In contrast to the extrusion-aged alloy, the enhancements in tensile yield strength and ultimate tensile strength of the E-5.6%CR-aged alloy were attributed to the combined effects of fine (beta^{prime }) precipitates, a high fraction of fine grains and high-density dislocations within the recrystallized and unrecrystallized grains. Although higher yield strengths can be obtained with a 9.6% rolling reduction, excessive rolling reduction is detrimental to tensile strength due to reduced elongation.

In the oil and gas extraction environment, the high CO₂ content and high salinity formation water will lead to simultaneous corrosion and scaling problems in the wellbore. The usage of corrosion and scale inhibitors is one of the effective methods to suppress the corrosion and scaling of pipelines in oil and gas fields. In this work, an imidazoline derivative (OA-IM-TU-HEDP) was synthesized as high-efficiency integrated corrosion and scale inhibitor for carbon steel in CO₂-containing formation water. The experimental tests show that OA-IM-TU-HEDP has outstanding corrosion and scale inhibition effects, with the corrosion inhibition efficiency more than 97% in supercritical CO₂ environment at 120 °C and scale inhibition efficiency more than 90%. Quantum chemical calculations show that the introduction of thiourea and phosphonic acid groups into imidazoline corrosion inhibitor can significantly increase the adsorption sites and then effectively improve the adsorption performance of OA-IM-TU-HEDP. Molecular dynamics (MD) simulations indicate that OA-IM-TU-HEDP molecules could adsorb on the steel surface with the imidazoline ring, thiourea fragment, and phosphonic acid group, which can effectively prevent corrosive species from reaching the steel surface, thereby suppressing steel corrosion. In addition, OA-IM-TU-HEDP molecules can adsorb on CaCO₃ surface through phosphonic acid group to prevent the further growth and accumulation of CaCO₃ scale, thereby effectively inhibiting the formation of CaCO₃ scale.

To enhance the durability of CuPb10Sn10 anti-friction coatings on the slipper-swash plate pair in axial piston pumps, this study fabricated CuPb10Sn10 coatings using a two-step process combining laser cladding and laser remelting (LR). The influence of LR laser power (1100-2000 W) on the microstructure, hardness, and wear resistance of the coatings was systematically evaluated, alongside the underlying mechanisms. Experimental results demonstrated that LR facilitates gas escape, reducing porosity by up to 76.3% (from 3.840% to 0.912%). LR enhanced coating hardness by 14.3% (reaching 116.51 HV at 2000 W) through grain refinement strengthening and defect elimination. Meanwhile, under a remelting power of 2000 W, the reduction of porosity at the coating bottom, coupled with the enhanced metallurgical bonding, increased the coating–substrate interfacial bonding strength from 150.3 MPa to 162.7 MPa. Phase analysis confirmed that the coatings retained Cu, Pb, and the Cu₄₁Sn₁₁ phase, with no new compounds formed. However, higher remelting power promoted precipitation of the Cu₄₁Sn₁₁ phase. Wear resistance significantly improved: At 2000 W, the coefficient of friction decreased by 4.4% (from 0.204 to 0.195), and wear loss was reduced by 23% (from 31.3 mg to 24.1 mg). Mechanistically, LR, by increasing density, enhancing hardness, and augmenting the Cu₄₁Sn₁₁ phase content, suppressed the dominant adhesive wear failure mode and promoted a shift toward predominantly abrasive wear. This study establishes a critical balance between defect suppression, microstructure optimization, and wear resistance enhancement. The findings provide actionable insights for improving the wear resistance of slipper-swash plate pairs.

In an earlier publication by the present authors, spatial and directional variations in material properties in a fabricated component were quantified using the results of miniature tensile specimens. The real-life applications of such material property variations are presented in this work. Specifically, the changes in the failure energy of a fastener and the burst pressure of a pipe are calculated, taking into account these directional and spatial variations in material properties. Two nuclear-grade materials are considered: SA333Gr6 and 20MnMoNi55 structural steels. Cohesive zone modeling is used to capture material damage near the failure of the components. The first case study, which examines fastener failure, shows wider variations in failure energy for the SA333 Gr6 material compared to 20MnMoNi55. Similar conclusions are drawn regarding the burst pressure variations of a pipe. These case studies underscore the importance of accounting for directional and spatial variations in material properties within a fabricated nuclear component. Such quantitative information aids designers in conducting conservative designs with appropriate safety margins and also performing structural integrity analyses considering that consider the weakest orientation of a crack in a plant component as is done in case of Leak-Before-Break evaluations of piping systems.