Search Results (174)

Yttria-stabilized zirconia(YSZ) was introduced into the Al₂O₃-TiO₂-CeO₂ coating prepared by plasma spraying to improve the wear resistance of the coating and prolong the service life of the weathering steel. The nano-agglomerated powder was prepared by mechanical ball milling and spray-drying technology, powder was sprayed on the surface of Q355 steel substrate by atmospheric plasma sparing (APS), the Al₂O₃-TiO₂-CeO₂/YSZ composite coating was prepared, and the effects of YSZ on the phase, microstructure, and tribological properties of the composite coating were studied. The results show that nano-agglomerated powders with micron size (average size 55 μm) can be prepared by spray-drying technology, and after high-temperature sintering, the nano-agglomerated powders are denser and form the α-Al₂O₃ phase. The composite coating prepared by plasma spraying has a bimodal structure, and after adding YSZ, the phases in the coating are mainly α-Al₂O₃, γ-Al₂O₃, and t-ZrO₂, the grain size is fine, and the porosity is reduced. The specific wear rate is only 4.4 × 10⁻⁵ mm³ N⁻¹·m⁻¹, the relative wear resistance is 6.3 times higher than that of the substrate, and the wear mechanism of the coating is mainly slight adhesive wear and abrasive wear, which shows excellent friction and wear properties at room temperature. Full article

Ultra-deep tight sandstone gas reservoirs are key targets for natural gas exploration, yet their pore structures under high temperature, pressure, and stress greatly affect gas occurrence and flow. This study investigates representative reservoirs in the Kelasu structural belt, Tarim Basin. Porosity–permeability were measured under in situ conditions, and multi-scale pore structures were analyzed using thin sections, a SEM, mercury intrusion, and nitrogen adsorption. The results show that (1) the median permeability of cores at an ambient temperature and a confining stress of 3 MPa is 13.33–29.63 times that under the in situ temperature and pressure conditions. When the core permeability is lower than 0.1 mD, the stress sensitivity effect is significantly enhanced; (2) nanopores and micron-fractures are well developed yet exhibit poor connectivity. The majority of a core’s porosity is derived from the intergranular pores in clay minerals; (3) the volume of nano-sized pores within the 100 nm diameter range is mainly composed of mesopores, with an average proportion of 73.37%, while the average proportions of macropores and micropores are 22.29% and 4.34%, respectively; (4) full-scale pore sizes show bimodal peaks at 100–1000 nm and >100 μm, which are poorly connected; (5) the pore structure exhibits distinct fractal characteristics. The fractal dimension D_f1 (2.65 on average) corresponds to the larger pore diameters of the primary intergranular pores, residual intergranular pores, and intragranular dissolution pores. The fractal dimension D_f2 (2.10 on average) corresponds to the grain margin fractures, micron-fractures and partial throats. The pore types corresponding to the fractal dimensions D_f3 (2.36 on average) and D_f4 (2.58 on average) are mainly intercrystalline pores of clay minerals and a small number of intraparticle dissolution pores. These findings clarify the pore structure of ultra-deep tight sandstones and provide insights into their gas occurrence and flow mechanisms. Full article

The development of low-cost and high-performance Mg alloys is an important way to achieve further application of magnesium alloys. In this work, the as-extruded Mg_98.3−xZn_xGd₁Sm_0.7 alloy with excellent mechanical properties is successfully prepared by regulating the bimodal-grained structure. The effect of the Zn content on the microstructure evolution and mechanical properties of the as-extruded Mg_98.3−xZn_xGd₁Sm_0.7 alloy is systematically investigated. The results show that the addition of Zn increases the dynamic recrystallization (DRX) fraction and weakens the basal texture of the as-extruded alloy. The Mg_98.05Zn_0.25Gd₁Sm_0.7 alloy exhibits a typical bimodal-grained structure. A large amount of geometrically necessary dislocations (GNDs) are generated at the interface between the soft zone and the hard zone of the bimodal-grained structure during the plastic deformation process, resulting in back stress strengthening, thereby improving the strength of the alloy. And it achieves exceptional mechanical properties with an ultimate tensile strength (UTS) of 330 MPa, a yield strength (YS) of 248 MPa, and an elongation (EL) of 18.5% at room temperature. This paper provides a new idea for introducing a heterogeneous structure and improving the strength of low-cost Mg alloys. Full article

Photosynthetic efficiency and dry matter accumulation are essential for achieving high rice yields, yet conventional controlled-release fertilizers often fail to synchronize nitrogen (N) supply with crop demand. In this study, we evaluated a novel double core–shell controlled-release urea (DCSCRU) designed to align with the bimodal N uptake pattern of rice. A two-year field experiment was conducted to compare DCSCRU at three application rates (180, 225, and 270 kg N ha⁻¹) with conventional urea and conventional controlled-release urea (both at 270 kg N ha⁻¹). DCSCRU exhibited a distinct biphasic N release profile, with a rapid initial release peaking at 1.60% d ⁻¹ on day 10 to meet early vegetative demand, followed by a second peak (1.85% d⁻¹ on day 45) supporting reproductive development. Compared with conventional urea, DCSCRU treatments significantly improved photosynthetic efficiency and dry matter accumulation during critical growth stages. The 270 kg N ha⁻¹ DCSCRU treatment achieved a grain yield exceeding 11.50 × 10³ kg ha⁻¹, substantially higher than that of conventional urea. Notably, the 225 kg N ha⁻¹ DCSCRU treatment produced a comparable yield (10.90 × 10³ kg ha⁻¹) to that of the conventional urea treatment (10.83 × 10³ kg ha⁻¹), indicating the potential to reduce N input by 16.7% without compromising yield. The enhanced physiological performance was attributed to improved N availability and optimized canopy function. These findings highlight DCSCRU as a promising strategy for high-yield, resource-efficient, and environmentally sustainable rice production. Full article

Biodegradable zinc alloys for orthopedic implants must balance mechanical strength and plasticity, yet current as-cast alloys struggle to meet this dual requirement. In this study, a Zn-3Cu-1Mg-0.3Nd alloy was designed, and the influence of room-temperature rolling at four reduction levels (50%, 60%, 70%, and 80%) on its microstructure and mechanical properties was systematically investigated. Results indicate that as the reduction increases, the CuZn₅ phase elongated along the rolling direction, and the η-Zn+Mg₂Zn₁₁ eutectic structure was progressively fragmented. The average grain size of the η-Zn matrix decreased significantly from 18.9 μm (50% reduction) to 1.71 μm (80% reduction). A distinct bimodal heterogeneous microstructure (coarse/fine grains) was formed at 60% and 70% reductions, while a predominantly fine-grained structure (91.3% fine grains) was achieved at 80% reduction. Furthermore, cracks initiated in the NdZn₁₁ phase due to stress concentration during rolling. As the rolling reduction increases, the alloy’s ultimate tensile strengths (UTS) initially rose and then declined (peaking at 417 ± 5 MPa at 60% reduction), while its elongation (EL) consistently improved. At 80% reduction, the alloy exhibited optimal mechanical properties, achieving a tensile strength of 406 ± 4 MPa and an EL of 16.4 ± 0.3%, both significantly higher than those of the as-cast alloy (126 MPa, 4.4%). The enhancement in strength is attributed to a multi-scale synergistic mechanism involving grain refinement and back stress strengthening induced by heterogeneous microstructures. The continuous improvement in plasticity results from grain refinement, texture weakening, and the activation of non-basal <c+a> slip systems. Notably, cracks within the NdZn₁₁ phase were confined by its high-binding-strength interface, preventing detrimental propagation into the matrix. This study elucidates the strengthening and toughening mechanisms in zinc alloys through cold rolling and the addition of the Nd element, particularly in terms of microstructural control and crack passivation, offering theoretical guidance for the design of biodegradable zinc alloy materials. Full article

In the quest to produce high-purity alumina, bottom-up engineering via architecting the interior of ceramic with bimodal structures of alumina powders in the absence of any additives has gained considerable attention owing to the simplicity offered. The present work investigated the influence of bimodal structures containing micron (~35 μm) and submicron (~600 nm) Al₂O₃ powders on the formation of dense Al₂O₃ ceramic. To this end, ball-milling was conducted to prepare the desired sizes of powders, followed by two-step sintering in a vacuum at 1450 °C and 1650 °C with 6 h and 4 h holding times, consecutively. The bimodal structures induced the formation of Al₂O₃ ceramic with nearly full densification (>99%; ρ 3.95 g/cm³). Both the coarse and fine-grained moieties synergistically balanced the densification kinetics whilst suppressing abnormal grain growth. The uniform and homogeneous grain size minimized the plasma porosity down to <6.0%, limiting the penetration of plasma during the etching process. Full article

This study investigates the microstructural evolution and mechanical response of an additively manufactured (PBF-LB/M) AlSi10Mg alloy subjected to severe plastic deformation via two passes of twist channel angular pressing (TCAP). Processing was conducted using Route Bc, with the first pass at 150 °C and the second at 250 °C. For the first time, the evolution from the initial hierarchical AM structure to a refined state was characterized in high-fidelity detail using a novel EBSD detector. The two-pass process transformed the initial structure into a heterogeneous, bimodal microstructure existing in a non-equilibrium state, characterized by a high fraction of low-angle grain boundaries (63%) and significant internal lattice distortion. The mechanical properties were dictated by the processing temperature: a single pass at 150 °C induced work hardening, increasing the yield strength from 450 MPa to 482 MPa. Conversely, the second pass at an elevated temperature of 250 °C promoted significant dynamic recovery. This led to a decrease in yield strength to 422 MPa but concurrently resulted in a substantial increase in ultimate compressive strength to 731 MPa. Full article

This study explored the effects of the finishing deformation temperature on the microstructure and properties of CrVNb micro-alloyed steel following thermomechanical processing (TMP). The investigation encompassed the influence of the deformation temperature on the ferrite grain size, precipitate characteristics, hardness and flow stress. The microstructure characterization was performed using optical and electron microscopy techniques. The results show that decreasing the deformation temperature refined the ferrite grains, though a bimodal ferrite grain structure formed when the deformation temperature fell to about 100 °C below the Ar3 temperature. Additionally, lower deformation temperatures increased the number density of strain-induced precipitates (SIPs), whereas the density of finer precipitates (random and interphase precipitates (IPs)) decreased. The highest hardness was observed in a sample deformed at 950–850 °C temperatures. These findings highlight the impact of the finishing deformation temperatures on the microstructural and mechanical properties, providing valuable insights for optimizing steel processing conditions. Full article

This study systematically investigates the influence of rolling temperature (cold rolling to 500 °C) on the microstructure and properties of Cu–10Fe alloy. The results show that with an increasing temperature, the Fe phase morphology transitions gradually from fibrous to spherical/ellipsoidal, while the Cu grain size first decreases and then increases. At 500 °C rolling, a bimodal structure forms (fine recrystallized grains coordinate deformation, and coarse grains provide strengthening), with dynamic recovery significantly reducing dislocation density, but the recrystallization rate remains only 11.9%. Texture analysis reveals that in the cold-rolled state, Brass-R texture (2.45) dominates, resulting in low elongation (1.96%). At 400–450 °C, the synergistic effect of Goss and Copper textures (6.9–13.82) improves elongation to 7.03%. At 500 °C, Brass texture (14.58) becomes dominant, increasing elongation to 9.21%, and tensile strength rises from 443 MPa to 472 MPa. Electrical conductivity increases from 10.09% IACS (cold-rolled) to 19.43% IACS (500 °C), mainly due to dynamic recovery and Fe precipitation alleviating lattice distortion. Full article

Wheat exhibits moderate tolerance to salinity. The increasing salinization of arable land poses a significant risk to future wheat production. Therefore, it is imperative to expedite the genetic breeding of wheat for enhanced salt tolerance. This study investigates the genetic and phenotypic diversity of 90 wheat varieties under salt stress, utilizing a comprehensive approach involving trait distribution analysis, hierarchical clustering, kinship estimation, and low-density association analysis. The phenotypic analysis of key agronomic traits revealed significant variability in traits such as leaf area index, canopy temperature, grain area, dry weight, harvest index, grain yield, and tiller number. Most traits exhibited a near-normal distribution, with a few parameters showing skewed or bimodal distributions, indicating the presence of subpopulations with distinct trait profiles. The hierarchical clustering analysis identified five distinct genetic clusters among the wheat varieties, highlighting the complex genetic relationships and variations in salt stress tolerance. Kinship estimates further confirmed the presence of genetic divergence among the accessions, with a majority showing weak or null relationships. Statistical models for association analysis revealed the effectiveness of the Generalized Linear Mixed Model (GLMM) in detecting a greater number of significant genetic markers associated with key agronomic traits, with the GLMM explaining a higher proportion of phenotypic variation. The findings underline the importance of genetic diversity in wheat breeding programs aimed at improving salt stress tolerance and agronomic performance. These results provide valuable insights for future breeding strategies, focusing on the optimization of key traits and marker-assisted selection for the development of salt-tolerant wheat cultivars. Full article

Magnesium alloys are essential lightweight materials for engineering applications. However, conventional single-phase hexagonal close-packed (HCP) magnesium alloys exhibit poor cold workability and insufficient strength at room temperature, which limits their engineering applications. Compared to HCP structures with limited slip systems at room temperature, body-centered cubic (BCC) structures possess 12 independent slip systems, enabling better plasticity. Therefore, Mg–Sc alloys with a dual-phase structure (HCP + BCC) exhibit superior plasticity compared to single-phase HCP magnesium alloys. In this study, the deformation behavior of dual-phase Mg-19.2 at.% Sc alloy was investigated, revealing its deformation characteristics and multiscale strengthening mechanisms. Experimental findings indicate that with the rise in annealing temperature, the volume fraction of the α phase progressively declines, while that of the β phase expands. Moreover, the grain size of the α phase first grows and then reduces, whereas the β phase grain size consistently enlarges. When the annealing temperature reaches 600 °C, the alloy exhibits an optimal strength–ductility combination, with an ultimate tensile strength of 329 MPa and an elongation of 20.5%. At this condition, the α phase volume fraction is 20%, while the β phase volume fraction is 80%, with corresponding grain sizes of 5.9 µm and 30.1 µm, respectively. Microstructural analysis indicates that the plastic incompatibility between the α and β phases induces significant heterogeneous deformation-induced (HDI) strengthening. Moreover, the unique bimodal grain size distribution, where the α phase grains are significantly smaller than the β phase grains, enhances the “hard phase harder, soft phase softer” heterogeneous structural effect, further amplifying the HDI strengthening contribution. This study provides new theoretical insights into multiphase interface engineering for designing high-performance dual-phase magnesium alloys. Full article

The existing Al-Ce heat-resistant alloys are not extensively utilized in high-temperature applications due to their poor room-temperature mechanical properties. In this study, the Al-10Ce-3Mg-5Zn alloy was enhanced using hot extrusion and heat treatment. The as-extruded alloy exhibited bimodal intermetallic compounds and grain structures. Additionally, high-density microcracks and twins were observed in the micron-sized intermetallic compounds. Compared with the as-cast state, the as-extruded alloy demonstrated a higher ultimate tensile strength (UTS) of 317 MPa and better elongation of 11.0%. Numerous nano-sized T phases precipitated in the α-Al matrix after the heat treatment, contributing to a further rise in UTS (365 MPa). The high strength of the alloy is primarily due to its strong strain hardening capacity, fine grain strengthening, and precipitation strengthening effect. The change in elongation mainly results from the expansion of pre-existing microcracks, twin deformation, and microstructural refinement. The heat-treated alloys exhibited superior strength retention ratios at elevated temperatures (64% at 200 °C) compared to conventional heat-resistant aluminum alloys. The results of this paper indicate that hot extrusion and heat treatment are effective for developing heat-resistant Al-Ce alloys with high room-temperature strength, offering a simple process suitable for industrial production. Full article

This study systematically investigates the heterogeneity of the Chang 6 reservoir in the Wuqi–Dingbian region of the Ordos Basin through integrated petrographic analysis using scanning electron microscopy (SEM), thin-section petrography, and mercury intrusion porosimetry. The results reveal that this feldspathic sandstone reservoir exhibits significant compositional and textural variations controlled by depositional environments. Dingbian samples displayed elevated feldspar (avg. 42.3%), lithic fragments (18.1%), and carbonate cementation (15.7%), accompanied by intense mechanical compaction and cementation processes. Pore systems in Dingbian were dominated by residual intergranular pores (58–62% of total porosity) and secondary dissolution pores. In contrast, Wuqi reservoirs demonstrated superior pore connectivity through well-developed intergranular pores (65–72%), grain boundary pores, and microfracture networks. Pore throat characterization revealed distinct architectural patterns: Wuqi exhibited broad bimodal/multimodal distributions (0.1–50 μm) with 35–40% macro-throat (>10 μm) contribution to flow capacity, while Dingbian showed narrow unimodal distributions (1–10 μm) with <15% macro-throat participation. These microstructural divergences fundamentally governed contrasting production behaviors. Wuqi wells achieved higher initial flow rates (15–20 m³/d) with 60–70% water cut, yet maintained stable production through effective displacement systems enabled by dominant macropores. Conversely, Dingbian wells produced lower yields (5–8 m³/d) with 75–85% water cut, experiencing rapid 30–40% initial declines that transitioned to prolonged low-rate production phases. This petrophysical framework provides critical insights for optimized development strategies in heterogeneous tight sandstone reservoirs, particularly regarding water management and enhanced oil recovery potential. Full article

Precise control of forging and heat treatment parameters is essential to achieve microstructural homogeneity in turbine disks, ensuring optimal mechanical performance for aerospace applications. This study examines the influence of the hot deformation temperatures on the grain size and γ′ phase characteristics of U720Li alloy following subsequent heat treatments. Samples extracted from a hot-extruded U720Li billet were subjected to isothermal compression within the temperature range of 1100–1130 °C, followed by holding at 1100 °C and 1120 °C for 4 h and air cooling. The results demonstrate that increasing the deformation temperature from 1100 °C to 1120 °C reduces the γ′ phase volume fraction at grain boundaries from 13% to 5%, weakens pinning effects, promotes grain growth during deformation, elevates grain boundary energy, and diminishes stored deformation energy, despite maintaining an equivalent degree of dynamic recrystallization. When the sub-solvus heat treatment temperature was 20 °C below the effective deformation temperature, Ostwald ripening dominated, resulting in a multimodal γ′ phase distribution after cooling. Conversely, when the sub-solvus heat treatment temperature 20 °C exceeded the effective deformation temperature, a significant portion of the intergranular γ′ phase dissolved, leaving a bimodal distribution comprising both large- and small-sized particles. Full article

This study explored the effects of T5 and T6 heat treatments on the microstructure and tensile properties of a laser powder bed fusion (LPBF)-fabricated Al–Mn–Mg–Sc–Zr alloy. The as-built condition exhibited a bi-modal grain structure of equiaxed and columnar grains. Specimens after T5 heat treatment also had a bi-modal microstructure with slight grain growth and the precipitation of secondary Al₃Sc, which enhanced the yield strength via precipitation hardening but reduced ductility. In contrast, T6 treatment triggered recrystallization, and the microstructure was only coarse equiaxed α-Al grains. This microstructure change was accompanied by coarsened primary Al₃X and Al₆(Mn, Fe) precipitates, partial Mg₂Si dissolution, and significant secondary Al₃Sc particle growth. Consequently, T6-treated specimens showed lower strength than their T5 counterparts and the poorest ductility due to brittle fracture induced by the stress concentration effect of coarse precipitates at grain boundaries. Full article