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Purpose: This paper aims to identify the optimal forming angle for the selective laser melting (SLM) process and evaluate the mechanical properties of the SLM-formed GH3536 alloy in the aero-engine field. Design/methodology/approach: Forming the samples with optimized parameters and analyzing the microstructure and properties of the block samples in different forming angles with scanning electron microscope, XRD, etc. so as to analyze and reveal the laws and mechanism of the block samples in different forming angles by SLM. Findings: There are few cracks on the construction surface of SLM formed samples, and the microstructure shows columnar subgrains and cellular subgrains. The segregation of metal elements was not observed in the microstructure. The pattern shows strong texture strength on the (111) crystal plane. In the sample, the tensile strength of 60° sample is the highest, the plasticity of 90° forming sample is the best, the comprehensive property of 45° sample is the best and the fracture mode is plastic fracture. The comprehensive performance of the part is the best under the forming angle of 45°. To ensure the part size, performance and support structure processing, additional dimensions are added to the part structure. Originality/value: In this paper, how to make samples with different forming angles is described. Combined with the standard of forged GH3536 alloy, the microstructure and properties of the samples are analyzed, and the optimal forming angle is obtained. [ABSTRACT FROM AUTHOR]

3D printing is an excellent choice for manufacture of ceramic cores; however, the inter-layer structures in 3D printed sample leads to anisotropy in microstructure and properties. In this paper, silica-based ceramic cores were prepared by digital light processing, and metallic Si powder was employed as mineralizer to relieve the anisotropy. The metallic Si powder converts into SiO 2 in oxidation reaction with significant volume expansion, which inhibits the shrinkage rate and partly fills the interlayer gaps of the ceramic core. Meanwhile, the metal Si powder leads to lower curing thickness in 3D printing, and thicken the interlayer gaps. Due to the cooperation of the oxidation reaction and decreased curing thickness by the metallic Si powder, the 0.4 wt% of metallic Si powder reduced the anisotropy in structure and mechanical property due to the alleviated inter-layer structure and the interlayer and intralayer strengths show optimal values of 11.4 MPa and 17.2 MPa at room temperature, respectively. This work inspires new guidance to 3D printing of ceramic cores with uniform microstructure and excellent mechanical properties. [ABSTRACT FROM AUTHOR]

The difference in microstructure leads to the diversity of shale mechanical properties and bedding fractures distribution patterns. In this paper, the microstructure and mechanical properties of Longmaxi marine shale and Qingshankou continental shale were studied by X-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM) with mineral analysis system, and nanoindentation. Additionally, the typical bedding layers area was properly stratified using Focused Ion Beam (FIB), and the effects of microstructure and mechanical properties on the distribution patterns of bedding fractures were analyzed. The results show that the Longmaxi marine shale sample contains more clay mineral grains, while the Qingshankou continental shale sample contains more hard brittle mineral grains such as feldspar. For Longmaxi marine shale sample, hard brittle minerals with grain sizes larger than 20 mm is 18.24% and those with grain sizes smaller than 20 mm is 16.22%. For Qingshankou continental shale sample, hard brittle minerals with grain sizes larger than 20 mm is 40.7% and those with grain sizes smaller than 20 mm is 11.82%. In comparison to the Qingshankou continental shale sample, the Longmaxi marine shale sample has a lower modulus, hardness, and heterogeneity. Laminated shales are formed by alternating coarse-grained and fine-grained layers during deposition. The average single-layer thickness of Longmaxi marine shale sample is greater than Qingshankou continental shale sample. The two types of shale have similar bedding fractures distribution patterns and fractures tend to occur in the transition zone from coarse-grained to fine-grained deposition. The orientation of the fracture is usually parallel to the bedding plane and detour occurs in the presence of hard brittle grains. The fracture distribution density of the Longmaxi marine shale sample is lower than that of the Qingshankou continental shale sample due to the strong heterogeneity of the Qingshankou continental shale. The current research provides guidelines for the effective development of shale reservoirs in various sedimentary environments. [ABSTRACT FROM AUTHOR]

Due to its lightweight, high strength, good machinability, and low cost, aluminum alloy has been widely used in fields such as aerospace, automotive, electronics, and construction. Traditional manufacturing processes for aluminum alloys often suffer from low material utilization, complex procedures, and long manufacturing cycles. Therefore, more and more scholars are turning their attention to the laser powder bed fusion (LPBF) process for aluminum alloys, which has the advantages of high material utilization, good formability for complex structures, and short manufacturing cycles. However, the widespread promotion and application of LPBF aluminum alloys still face challenges. The excellent printable ability, favorable mechanical performance, and low manufacturing cost are the main factors affecting the applicability of the LPBF process for aluminum alloys. This paper reviews the research status of traditional aluminum alloy processing and LPBF aluminum alloy and makes a comparison from various aspects such as microstructures, mechanical properties, application scenarios, and manufacturing costs. At present, the LPBF manufacturing cost for aluminum alloys is 2–120 times higher than that of traditional manufacturing methods, with the discrepancy depending on the complexity of the part. Therefore, it is necessary to promote the further development and application of aluminum alloy 3D printing technology from three aspects: the development of aluminum matrix composite materials reinforced with nanoceramic particles, the development of micro-alloyed aluminum alloy powders specially designed for LPBF, and the development of new technologies and equipment to reduce the manufacturing cost of LPBF aluminum alloy. [ABSTRACT FROM AUTHOR]

In this paper, by adding Co, Mo, and Ni metal binder and using spark plasma coupling high-frequency induction (SP–HF) sintering technology, high-entropy (W,Nb,Mo,Ta,Ti)C cermet with good performance was successfully prepared at 1350 °C. The sintering temperature was much lower than that of the solid-state sintering temperature adopted for high-entropy carbide ceramics (about 2000 °C) while maintaining high hardness and fracture toughness. The effects of sintering temperature, holding time and sintering pressure on the mechanical properties of high-entropy (W,Nb,Mo,Ta,Ti)C cermet were investigated. The experimental results show that the SP-HF sintering can promote the liquid phase flow inside the high-entropy (W,Nb,Mo,Ta,Ti)C cermet and improve the density. The high-frequency induction sintering effect of the high-intensity magnetic metal binder phase (Co, Ni) promotes the rapid diffusion of the constituent phases using the vacancy mechanism and the metal liquid phase, which helps to form a high-entropy cermet solid solution at a lower temperature. The different high-entropy effects of the inner and outer layers of high-entropy (W,Nb,Mo,Ta,Ti)C cermet materials play a role in strengthening and toughening the materials, and effective solid solution strengthening is the main reason for improving mechanical properties. The mechanical properties of high-entropy (W,Nb,Mo,Ta,Ti)C cermet are the optimized at 1350 °C, holding time of 8 min, and sintering pressure of 35 MPa. The Vickers hardness, fracture toughness, and flexural strength are 18.38 ± 0.19 GPa, 9.65 ± 0.25 MPa · m1/2 and 970 ± 30 MPa, Vickers hardness was measured at 49 N load. [ABSTRACT FROM AUTHOR]

Retrogression and re-aging (RRA) treatment has been proven to effectively overcome the trade-off between strength and corrosion resistance. Current research focuses on the heating rate, temperature, and holding time of retrogression treatment while ignoring the retrogression cooling ways. In this paper, the effects of RRA treatment with different retrogression cooling ways on the microstructure and properties of newly developed T'/η' strengthened Al-Zn-Mg-Cu alloys were investigated by performing tests on mechanical properties, intergranular corrosion (IGC) resistance, and electrochemical corrosion behavior. The results show that the mechanical properties of samples subject to RRA treatment with water-quenching retrogression (ultimate tensile strength, yield strength, and elongation of 419.2 MPa, 370.2 MPa, and 15.9, respectively) are better than those of air-cooled and furnace-cooled samples. The corrosion resistance of water-quenching (IGC depth of 162.2 μm, corrosion current density of 0.833 × 10−5 A/cm2) and furnace-cooled samples (IGC depth of 123.7 μm, corrosion current density of 0.712 × 10−5 A/cm2) is better than that of air-cooled samples. Microstructure characterization reveals that the effect of the retrogression cooling rate on mechanical properties is related to the size of T'/η' precipitates with grains as well as the proportion of T' and η', while the difference in corrosion resistance depends on the continuity of grain boundary precipitates (GBPs). With mechanical properties, corrosion resistance, and time cost taken into consideration, it is appropriate to select water quenching for retrogression. These findings offer valuable insights for further design to achieve superior performance in various applications. [ABSTRACT FROM AUTHOR]

Due to the problems of low welding efficiency, large heat-affected zone, and poor welding quality in the process of welding thin-walled titanium tubes by argon arc welding, there are few studies on the use of high-frequency induction welding (HFIW) of thin-walled titanium alloy tubes. The evolution law of weld microstructure and mechanical properties of the thin-walled titanium tube needs to be further studied because of rapid welding speed and the small heat-affected zone of HFIW. Therefore, a novel manufacturing method via high-frequency induction welding is proposed in this paper to solve the existing problems. With an industrial-grade titanium TA2 tube (wall's thickness is 0.5 ​mm) as the research object, a comparative study is conducted in this research to examine the morphology, microstructure, microhardness, and tensile characteristics of welded joints at different welding power. The findings demonstrated a significant efficacy of HFIW in resolving these challenges. The mechanical properties and microstructue of heat-affected zone (HAZ) were characterized. The lowest hardness is measured at 202 HV, while the base material was recorded as 184 HV, when the welding speed of HFIW is set at 50 ​m/min. Meanwhile, the heat-affected zone has the highest hardness at 224 HV, a tensile strength of 446.8 ​MPa and a post-fracture elongation of 16%. The results showed that HFIW can not only greatly improve the welding efficiency, significantly improve the microstructure of weld joint and HAZ, and improve the mechanical properties of thin-walled titanium pipe, but also provide a highly feasible welding method for welding ultra-thin-walled pipes. • A novel method of high-frequency induction welding has been employed to achieve the welding of thin-walled pure titanium pipe. • An in-depth analysis of the microstructure of the welded joints was conducted, revealing the robust applicability of the technique. • Through the analysis of the mechanical properties of the welding, the results show that good expectations are obtained. [ABSTRACT FROM AUTHOR]

Ceramic aerogels are attractive for their promising applications in thermal insulation, ultrafiltration, catalysis, and many other areas, owing to their high porosity, low density, high specific surface area, low thermal conductivity, and thermal stability. However, the practical applications of conventional ceramic aerogels are usually impeded by brittleness. Resilient ceramic aerogels overcame the brittleness of conventional ceramic aerogels and realized reversible compressibility, but they usually show brittleness under tensile stress and limited load‐bearing ability. In this short review paper, we reviewed the strategies to modify the mechanical properties of resilient ceramic aerogel. These strategies were achieved through tuning the deformation and moving ability of the nanowire building blocks and the deformation resistance provided by the aerogel architecture. Perspectives for further modifying the mechanical properties of resilient ceramic aerogel are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, the Al–K2ZrF6–KBF4 reaction system, a melt reaction method, was used to prepare in situ ZrB2/AA6111 particle-reinforced aluminum matrix composite. The modification of friction stir processing (FSP) and T6 heat treatment (HT) was carried out for this composite for the first time. The reinforcing particles in the stirring zone after FSP+HT were refined from 1.7–1.9 to 0.1–0.3 μm. The grain size was refined from 10–50 to 2–5 μm and then slightly coarsened to 3–10 μm. The tensile strength of the FSP stirring zone is 193.40 MPa, the elongation is 29.33%, and the average hardness is 60 HV. The hardness of the stirring zone is not uniform and fluctuates in a large range of 53–80 HV. After the T6 heat treatment, the tensile strength of the stirring zone increased by 63.8% to 316.75 MPa. The tensile strength was 13% higher than that of T6-6061. The elongation remained at 30.12% and did not decrease. The elongation is 10% higher than that of other 6xxx aluminum alloys and composites after T6 heat treatment. The plasticity-reduction of the conventional alloy after T6 heat treatment was solved. The property is more uniform and the average hardness is 120 HV. Calculated by the theoretical model, the yield strengths of the stirring zone of the original composite, FSP, and FSP+HT composites were more than 96% consistent with the experimental values. [ABSTRACT FROM AUTHOR]

The development of fiber-reinforced polymer (FRP) composites, striking a balance between high strength and toughness, is a pressing requirement for the contemporary aerospace industry. Regarding the design of microstructures for enhancing strength and toughness, bionic crossed-lamellar and bouligand structures serve as noteworthy examples. However, individual biomimetic microstructures have approached the upper limit of their strengthening and toughening effects. This paper firstly proposed a "Meta-Biomimetic" design concept : hybridizing biological microstructures with defensive functionalities and those with offensive functionalities in mechanical design, aiming to achieve a metamaterial with both offensive and defensive capabilities. Namely this work retains the three-layer cross-lamellar microstructure of conch shells to stimulate subcritical damage for enhanced energy dissipation, while introducing a bouligand microstructure of lobster homarus americanus to increase the high load-bearing capacity at both tension and compression ends. The optimal design for enhancing the strength and toughness is the three-layer crossed-lamellar microstructure modified with a full bouligand structure, which increases strength and toughness simultaneously by more than 500% compared to natural structures. These studies are poised to not only steer the design of FRP microstructures towards enhanced strength and toughness but also furnish a foundation for interdisciplinary research in biomimetics within composite materials. [Display omitted] [ABSTRACT FROM AUTHOR]

In order to reduce the weak area caused by traditional connection method and improve the structural efficiency of aircraft, the design concept of an integral component with dual microstructure is proposed. The electropulsing treatment (EPT) was used to produce an axial gradient microstructure (AGM) in TC21 titanium alloy, followed by the step-quenching treatment (SQT) to tailor the precipitation behavior of the α phase. Results demonstrate that the AGM produced by the combination of EPT and SQT achieves a simultaneous enhancement in both strength and plasticity of the alloy. Compared to EPT alone, the SQT results in the dissolution of the bimodal microstructure region with small-sized α phase, and an increased density of secondary α phase precipitation in both the transition and lamellar microstructure regions. During room temperature tensile deformation, coordinated distribution of deformation occurs sequentially in various regions, the 10 1 ̅ 0 11 2 ̅ 0 type of prismatic slip and deformation nanotwins exist in the equiaxed and lamellar α phase, respectively. Moreover, the deformation gradually declines from the bimodal region to the lamellar region, leading to the fracture of AGM in the bimodal region and an overall augmentation of the strength and plasticity of TC21 alloy. Hence, the results of this paper can provide research basis for the strength and plasticity improvement and deformation damage mechanism of high strength and toughness titanium alloy. • SQT significantly improved the nucleation rate of the lamellar α phase and formed discontinuous grain boundary α phase. • TC21 alloy with AGM manufactured by EPT and SQT achieved a simultaneous enhancement in strength and ductility. • Dislocation slip and TWIP effect in different regions form the coordinated distribution of deformation. • The result is significant importance in designing and researching for gradient structural materials. [ABSTRACT FROM AUTHOR]

The mechanical properties and durability of concrete are significantly affected by early frozen, during the early curing phase, concrete has a relatively low initial strength, and its hydration reaction rate is impeded by the early frost stage, leading to internal water freezing and subsequent expansive stress. The freezing and expansion deformations induce crack formation in the concrete structure. Even if positive-temperature curing is implemented for a specific period, some deformations remain irreparable, significantly compromising the mechanical properties and durability of concrete. Research on early frozen concrete mainly focus on water-cement ratio, freezing temperature, curing age, and additive dosage, which have different effects on the mechanical properties, durability, and microstructure of concrete. This paper systematically summarizes and analyzes the effects of early freezing on the mechanical properties and durability of concrete subjected to early frozen at home and abroad, and predicts and analyzes its future research directions and trends in this field. • Influences of early frost on the mechanical properties, durability, and microstructure of concrete are reviewed. • Effects of different admixtures and dosages on early frozen concrete are discussed. • The directions for further research on the effect of early frost on concrete are proposed. [ABSTRACT FROM AUTHOR]

The semi-solid slurry preparation process, microstructure, and mechanical properties of truck coarse filter bracket were studied in this paper. The semi-solid aluminum alloy slurry with high solid fraction was prepared by the Slurry Enthalpy Equilibrium Device (SEED) method, and the optimum slurry preparation parameters were determined through the observation and analysis of the slurry microstructure as follows: pouring temperature 700 °C, rotation speed 180 r/min, and crucible temperature 400 °C. The average grain size and shape factor of the slurry prepared under these conditions are 50.448 μm and 0.799. Die casting trial production which used the best process parameters of slurry preparation and die casting was carried out. The results show that the die casting parts are completely filled with no obvious surface defects. It can be seen from the cutting experiment and X-ray non-destructive test that the internal structure is dense and uniform, and there are no obvious casting defects that were observed such as cracks and holes. The semi-solid die castings were strengthened by T6 heat treatment. The experimental results showed that the optimal heat treatment parameters were a solution temperature of 470 °C and time of 4 h, aging temperature of 175 °C and time of 12 h. Under these conditions, the microstructure morphology was improved significantly. The tensile strength and yield strength reached 342.1 MPa and 309.1 MPa, respectively, which were 38.9% and 95.3% higher than the semi-solid state, and the elongation was 4.5%. [ABSTRACT FROM AUTHOR]

The uncontrollable directional grain growth and non-equilibrium microstructure of Inconel 718 will form during laser direct energy deposition (LDED), which seriously limits the promotion and application, so it is necessary to consider the heat treatment to improve the microstructure and mechanical properties. In this paper, the effects adopting different heat treatments on the phase composition, precipitation behavior, grain structure, tensile and tribological properties of LDED Inconel 718 have been systematically investigated, with as-deposited samples compared. The results show that the number and size of γ″ phases can be significantly changed under different aging and solution conditions, and the strength and wear resistance increase while elongation decreases since the fine grain and precipitation strengthening occurring during heat treatment. By comparing the different samples, the SA1100A exhibits the highest yield and tensile strength, with 140.6% of yield strength and 83.9% of ultimate tensile strength increasing compared to as-deposited samples, also showing the narrowest wear mark width and the lowest average mass loss. [ABSTRACT FROM AUTHOR]

In this paper, we designed a new L1 2 nanoparticles-strengthened fcc-structured (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA. The high-density L1 2 nanoparticles with an average size of ∼57 nm are uniformly distributed in the grain with an average size of ∼37 μm. The volume fraction of L1 2 nanoparticles is up to ∼45%. The L1 2 nanoparticles can be identified as the (Ni,Co,Cr) 3 (Ti,Al) multi-component phase. Compared to the single-phase Co 2 Ni 2 Cr base alloy with a yield strength of ∼208 MPa and an ultimate tensile strength of ∼660 MPa, (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA possesses a much higher yield strength of ∼1125 MPa and an ultimate tensile strength of ∼1540 MPa while retaining an excellent ductility of ∼38%. The precipitation strengthening by L1 2 nanoparticles takes the largest contribution to the yield strength, and the contribution value is up to ∼712 MPa. The deformation mode is dominated by mechanical twins for Co 2 Ni 2 Cr base alloy and (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA, and the mechanical twins are more prevalent in the Co 2 Ni 2 Cr base alloy. • A new L1 2 nanoparticles-strengthened (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA is well designed. • The volume fraction of L1 2 nanoparticles with a mean size of ∼57 nm is up to ∼45%. • (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA has an excellent property (σ s ∼ 1125 MPa, σ b ∼ 1540 MPa, δ ∼ 38%). • L1 2 nanoparticles precipitation strengthening takes the largest contribution to strength. • The deformation mode is dominated by mechanical twins for (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA. [ABSTRACT FROM AUTHOR]