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Titanium alloys, which are widely used in aerospace materials, have low thermal conductivity, leading to difficulty in hot forging. In particular, process parameters such as deformation temperature and strain rate significantly contribute to the deformation behavior of the microstructure and directly affect the mechanical properties. Therefore, to evaluate the formability by simulating a hot forging process that forms uniform and fine grains, the Ti-5Mo-4Fe alloy was tested using hot compression at deformation temperatures of 700–950 ℃ and strain rates of 0.001–1/s. Depending on the process parameters, the alloy exhibited microstructural changes such as lamellar kinking, dynamic spheroidization, dynamic recrystallization, and grain growth. Additionally, by easy dynamic spheroidization and dynamic recrystallization of the fine initial lamellar structure by the addition of Fe, grains with an average size (diameter) of 7 μm or less were formed after hot compression. The study identified the conditions of 750 ℃, 1/s and 900 ℃, 1/s as the optimal process conditions, under which the dislocation density was effectively resolved and a number of fine grains were observed. • A study on influence of several hot forging process variables in metastable Ti-5Mo-4Fe alloy. • Effect of deformation temperature, strain rate on the occurrence of two recrystallization mechanisms (CDRX, DDRX). • Dynamic recrystallization with grain size distributions ranging from 1 to 10 um and from 10 to 100 um. [ABSTRACT FROM AUTHOR]

Nickel-based powder superalloys have become one of key materials for aerospace turbine engines due to their excellent comprehensive properties. The microstructure stability during long-term isothermal aging is closely related to mechanical properties. The correlation between order phase transition and mechanical properties of a HIP (hot isostatic pressing) nickel-based powder superalloy after long-term isothermal aging treatment was investigated. The results show that the decomposition of MC carbides and precipitation, growth and coarsening of γ' phases occur with duration of isothermal aging. Tertiary γ' phases precipitates by the way of element diffusion with γ' phases coarsening. In addition, strengthening mechanism is quantitatively calculated, and the relative contribution of γ' phases to yield strength is largest, and multi-mode size of γ' phases are favorable to yield strength and hardness of HIP nickel-based powder superalloy. • PPBs decrease and MC + γ → M 23 C 6 + γ' transition occurs during isothermal aging. • The tertiary γ' phases burst out during long-term isothermal aging. • The effect of order phase transition on mechanical properties is explained. • γ' phases with multi-mode size are beneficial to improve tensile properties. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo), characterized by its high melting point, low thermal expansion coefficient, and excellent electrical and thermal conductivities, is widely considered an ideal metal material for applications in aerospace, nuclear fusion, electronics, and medical fields. Nevertheless, the major drawback of pure Mo is its significant brittleness, which restricts its practical utilization. This work presents a comprehensive review of the research progress on Mo alloys in recent years, covering preparation routes from composite powder preparation to advanced sintering technologies as well as performance evaluations (including mechanical properties and oxidation resistance). Additionally, it offers an outlook on the research prospects and development directions of Mo alloy composition design and preparation routes. [ABSTRACT FROM AUTHOR]

The article reviews the development, current use, and future potential of magnesium alloys in the aerospace industry. Magnesium alloys are valued for their high specific strength, stiffness, excellent damping properties, electromagnetic shielding, and thermal conductivity. These properties make them particularly useful for manufacturing critical components in aircraft, missiles, and spacecraft, as they reduce weight and enhance performance. China is a leading producer of magnesium alloys, with substantial use in aerospace, contributing to lighter aircraft and spacecraft, improved maneuverability, and lower launch costs. Despite their advantages, magnesium alloys face challenges, including poor corrosion resistance, low strength at high temperatures, and casting difficulties. The paper discusses the evolution of magnesium alloys, noting their early use in the 20th century and a resurgence in the 1990s. It highlights ongoing research to develop magnesium-rare earth (Mg-RE) alloys, which offer better strength and high-temperature resistance. The paper also outlines the limitations of magnesium alloys compared to aluminum alloys, which remain dominant due to superior overall performance. In the future, advancements in surface treatments, manufacturing processes, and alloy compositions are crucial for overcoming current limitations, enabling broader use of magnesium alloys in aerospace applications. [ABSTRACT FROM AUTHOR]

AA7475 aluminum alloy is used as a structural material in aerospace and automobile applications where complex loading conditions are applicable. The material properties under multi-axial loading are recommended for efficient component design. Hence, the mechanical behaviour of AA7475-T761 aluminium alloy was investigated through planar biaxial tensile tests. The yield locus evolution and plastic strain direction were measured at higher plastic strain values (up to 7 %) at various load ratios. The yield loci were constructed and compared with existing yield criteria. Yld2000–2d yield criterion demonstrated accurate predictions with a deviation of approximately 1 %, highlighting its effectiveness in capturing the yield behavior of AA7475. Microstructure analysis using Electron Backscatter Diffraction (EBSD) was conducted to understand the misorientation evolution under the multi-axial loading. Bulk-texture analysis was performed using X-ray diffraction method. Texture analysis revealed that uniaxial deformation favoured the development of Cube and Inverse-Copper textures, while biaxial deformation yielded split Inverse-Goss texture formation. Fractography study shows very different fracture surfaces of biaxial samples compared to uniaxial samples. Overall, this study contributes to a comprehensive understanding of the yield behavior, microstructure, and texture evolution of AA7475-T761 aluminium alloy under different loading conditions at very large strains. [Display omitted] • Biaxial tensile test and yield locus evolution of AA 7475-T761 at different load ratios using cruciform specimen. • The Yld2000–2dcriterion gives accurate predictions of yield loci for AA 7475(∼1 % error). • Fracture is most likely to initiate because of the shearing of the second phase particles under biaxial loading. • Equi-biaxial sample shows a higher fraction of inverse Goss texture (5.08 %). • Splitting of the inverse Goss texture in load ratio of 2:1 and 4:3 due to the anisotropy present in the material. [ABSTRACT FROM AUTHOR]

Ti–22Al–25Nb intermetallic alloy is the latest generation of lightweight aerospace material with superior high-temperature performance. In the present study, a novel hybrid 3D-printing technique, point-forging and laser-deposition (PF-LD), was adopted for demonstrating its possibility in the preparation of near-net-shaping Ti–22Al–25Nb component. We innovatively exploited the top ductile B2/β-phase-zone as a natural protective layer, successfully preparing Ti–22Al–25Nb intermetallic parts with relatively larger build-height without initiating any macro-micro cracks. Three groups of control trials were further performed to ascertain the effect of initial laser parameters on microstructural characteristic and mechanical performance. Among three deposition strategies, the sample with intermediate laser scanning rate reached the best combination of ultimate tensile strength (UTS: ∼ 1280.7 MPa) and elongation after failure (EL: ∼ 5.7 %), while superior tensile strength (UTS: ∼ 1314.8 MPa) could be also achieved at the expense of tensile ductility (EL: ∼ 2.4 %). This study not only reveals a new idea to low-temperature forming Ti–22Al–25Nb alloy, but also provides an insight into the relationship between PF-LD processing parameters and mechanical performance. • PF-LD is a novel hybrid 3D-printing technique which introduces point-forging into the process of conventional laser-deposition. • Ti 2 AlNb intermetallic sample with relatively-larger build height was successfully prepared by hybrid PF-LD technique. • The influence mechanism of initial laser parameters on microstructural evolution and mechanical properties was discussed. [ABSTRACT FROM AUTHOR]

Refractory high-entropy alloys (RHEAs) composed of Ti, Zr, Hf, and Nb have emerged as promising materials for high-temperature aerospace applications due to their exceptional balance of strength and toughness, coupled with a reduced density and softening resistance. This study delves into the influence of alloy composition on the mechanical properties, a pivotal aspect in the design of RHEAs. We investigate a series of Ti 48-x Zr x Hf 26 Nb 26 (x = 14, 18, 22, 26, 30, 34) alloys, prepared through suction casting and homogenization treatments. The phases, microstructure, and fracture morphology of these alloys are analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD), subsequent tensile tests provide insights into the strength and elongation characteristics of alloys. The homogenized alloys consistently exhibit one BCC phase with equiaxed grains, whereas the fracture mode shifts from intergranular to transgranular, and return to intergranular as the Zr content increases. Experimental results reveal an asymmetry mechanical behavior, alloys with higher Ti content display superior toughness (elongation 17.83 % for Ti = 34 at%) compared to those with higher Zr content (elongation 16.05 % for Zr = 34 at%). Among them, the Ti 22 Zr 26 Hf 26 Nb 26 alloy achieves the peak tensile strength of 695.25 MPa, indicating an inverse relationship between strength and toughness. Solid-solution strengthening and chemical short-range orderings emerge as the predominant contributors to the overall strength of the TiZrHfNb alloys. To gain a deeper understanding of the mechanical behavior at the atomic scale, we performed first-principles calculations to investigate the elastic properties and charge density of Ti 48-x Zr x Hf 26 Nb 26 alloys in the BCC structure. These calculations shed light on the underlying mechanisms governing the strength and toughness behavior. The present work offers valuable insights into the design of mechanical properties of TiZrHfNb RHEAs, serving as a paradigm for future materials development in this field. • Microstructure and mechanical behaviors of TiZrHfNb RHEAs are investigated. • The asymmetrical tensile strength and elongation exhibited, alloys with a lower content of Zr have superior toughness. • DFT calculations of the elastic modulus and charge density are performed to elucidate the experimental findings. • CSROs and solid-solution strengthening significantly contribute to tensile strength, the peak value reaching 695.25 MPa. [ABSTRACT FROM AUTHOR]

Selection and utilization of multifaceted coating materials for progressing aerospace and defence technologies that operate in stringent service environments are always challenging. Nevertheless, conventional coatings exhibit limited strength, flexibility, durability, and poor substrate-coating adhesion when exposed to extreme adverse temperatures, formidable fatigue and creep, huge vacuum, and swift velocity. Currently, researchers are increasingly attracted towards the newly emerging single-layered (2D) materials for their structure-property relationship to utilize them as a protective coating that renders prospective outcomes for these concerns. Therefore, this review focuses on various attributes of the atomically thin-Angstrom scale 2D materials such as MXene, hexagonal-BN, graphene, transition metal dichalcogenides (TMD) including WS 2 , MoS 2 , TiN, and WSe 2 , black phosphorous, and borophenes. A thorough investigation of their lower thermal conductivity (0.16–1.752 W/m/K) when operated between − 10 °C and an elevated temperature of 1100 °C offering exceptional thermal barrier effects, the ultra-low coefficient of friction (0.06–0.6) under different sliding conditions inducing excellent anti-wear/anti-friction behaviour, and the minimum corrosion rate (2.24 × 10-3 to 0.086 mm per year) in varying atmospheric conditions instigating corrosion passivation of the 2D nanomaterials deposited over metallic substrate have been elucidated. These exceptional properties of atomically thin nanomaterials can be potentially utilized in engine components, piston-cylinder linings, and landing gears of aerospace systems, heat exchangers, flanges, and impellers in the marine sector and potentially utilised in muzzle, recoil springs, and barrels of armament technologies. [Display omitted] [ABSTRACT FROM AUTHOR]

Al-Cu-Mg alloys, as important aircraft skin material in the aerospace field, should have excellent corrosion resistance and lower chemically-milled surface roughness. Fortunately, we found that microalloying with Zr elements can solve the challenges. In this work, the effects of adding the Zr to Al-3.8Cu-1.2Mg alloys the microstructural evolution, intergranular corrosion (IGC), electrochemical corrosion and chemically-milled surface roughness are investigated by using OM, SEM, and TEM studies. The electrochemical measurements tests are performed using a CHI760 electrochemical testing instrument and the chemically-milled surface roughness is measured by JB-4 C precision roughness tester. The experimental results show that the Zr additions to Al-3.8Cu-1.2Mg alloy could refine grain size, improve solidification segregation, increase the spacing of grain boundary precipitation phases, enhance corrosion resistance, and optimize the chemically-milled surface roughness. It is found that with the increase of Zr content, the precipitate-free zones (PFZs) of the alloy gradually become narrower and the grain boundary precipitation phases (GBPs) are discontinuously distributed. In addition, a narrower PFZ and discontinuous GBP are beneficial to enhance the IGC resistance of the alloy. The alloy with 0.2 wt% Zr exhibits the best corrosion resistance and the lowest chemically-milled surface roughness. The finding provides a good strategy for the high corrosion resistance and superior chemically-milled surface roughness properties for applications as aircraft skin material in the aerospace field. • The addition of Zr elements can refine the grain size and improve the dendrite segregation of the cast Al-Cu-Mg alloys. • Microalloying of Al-Cu-Mg alloy with Zr elements can reduce the corrosion susceptibility of the alloy. • The minor of Zr additions can optimize the chemically-milled surface roughness of Al-Cu-Mg alloys. [ABSTRACT FROM AUTHOR]

The rare-earth (RE) contained ultrafine grained (UFG) Magnesium (Mg) alloys are excellent materials for aerospace and automobile industries due to their ultra-light weight, high strength, reduced tension to compression yield asymmetry, etc. Despite their excellent properties, the manufacturing potential of UFG Mg-RE alloys is yet to be realized. The present work is focused on engineering UFG microstructure in a Mg-Ag-Nd alloy (a Mg-RE alloy) and establishing the manufacturing potential of such engineered UFG Mg-RE alloy via processing map and constitutive analysis studies. The processing map is developed for a temperature range of 300 °C-450 °C and a strain rate range of 0.001 s−1-1 s−1, respectively. Three stability domains and one instability domain were identified. The governing mechanisms and scientific know-how of both types of domains are established via mechanical testing followed by detailed microstructural characterization, including Electron Backscatter Diffraction (EBSD) and Transmission Electron Microscopy (TEM) analysis. A unique unexplored grain boundary sliding (GBS) mechanism-based stability domain is found as a dominant mode of deformation in one of the stability domains in the engineered UFG Mg-RE alloys. • Processing map (PM) with constitutive analyses explains manufacturability of UFG Mg-RE alloys. • Superplastic manufacturability domain is established for rapid manufacturing of UFG Mg-RE alloys. • Results of PM and texture explain micro-mechanism for UFG Mg-RE in wide temperature and strain-rate ranges. [ABSTRACT FROM AUTHOR]

PAN-based carbon fibers have been widely used in aerospace materials due to high specific strength, high specific modulus and many other outstanding features. As one kind of carbon-based electromagnetic wave (EMW) absorption material, carbon fibers are expected to absorb more EMW due to multiple polarization losses and large specific surface area in which EMW can be reflected many times. However, they also have certain disadvantages when used as EMW absorption material due to their high dielectric constant, low permeability and low reflection loss strength. Herein, a facile hydrothermal synthesis method was used to construct the three-dimensional (3D) bimetal-organic framework compound onto the surfaces of polyacrylonitrile(PAN)-based ultrahigh modulus carbon fibers (UHMCFs). Through the control of key parameters in the synthesis process, 3D bimetallic ZIF particles with different morphologies were assembled on the fiber surfaces, and a further high temperature heat treatment resulted in significantly improved EMW absorption properties. The results showed that three fibrous structures including rod-shaped, threadlike and flower-like morphologies had been formed with the introduction of CoZn-ZIFs. Among them, the uniform structure of rod-shaped sample could be preserved after carbonization and it also showed optimal EMW absorption performance, e.g. its minimum reflection loss (RL min) and effective absorption bandwidth (EAB) values were − 67.67 dB (EMW loss above 99.9 %) and 4.28 GHz, respectively, with the thickness of 2.00 mm. In the final, the EMW absorption mechanism of CoZn-bimetallic ZIF decorated UHMCFs including interfacial loss, conductive loss, polarization loss, multiple scattering and excellent impedance matching was discussed in detail. • 3D bimetallic ZIFs were assembled on the surfaces of ultrahigh modulus carbon fibers. • High-temperature heat treatment could improve EMW absorption properties. • The rod-shaped sample showed optimal EMW absorption performance. • The minimum reflection loss of fiber sample reached − 67.67 dB (EMW loss above 99.9 %). [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced aluminum matrix hierarchical composites have attracted the attention as a potential lightweight material for aerospace. Two typical C f /Al composites were prepared by pressure infiltration method with changing the infiltration pressure. The analysis of microstructure, mechanical properties and failure behavior were carried out to systematically reveal the damage mechanisms of composites to realize their full potential. The results show that the infiltration process and solidification behavior of composites can be revealed by analyzing the evolution law of macrosegregation and microstructures. Compared with the matrix alloy, the bending strength of H-C f /Al composites increased by 47%, and the compression strength of P-C f /Al composites increased by 128%. To clarify the crack propagation behaviors of H-C f /Al composite, toughening mechanisms such as crack deflection, crack bridging, and crack branching are discussed. The shear tests show that the failure characteristics of H-C f /Al composites are mainly fiber bundle interface cracking, while the strong interlaminar shear strength of P-C f /Al composites dominated by fiber splitting is attributed to serious interface reaction. In addition, main damage mechanisms affecting the ultimate failure were identified, namely interface splitting cracks, plastic deformation of matrix and fiber damage. This study provides meaningful enlightenment for the preparation and application of fiber-reinforced metal matrix composites. • It is revealed that fiber-induced Al 2 Cu phase grows preferentially along the (110) plane. • Compared with the matrix, the bending strength of H-C f /Al increased by 47%, and the compression strength of P-C f /Al increased by 128%. • For H-C f /Al composites, it is emphasized that fiber bundles are considered to be the stress concentrators on the microscopic scale. • It is revealed that high volume fraction of fiber reinforcement incompletely weakens the mechanical properties of hierarchical composites. • The failure behavior and damage mechanism of C f /Al composites are systematically revealed. [ABSTRACT FROM AUTHOR]

The use of high-performance, lightweight advanced materials in aerospace equipment construction can reduce weight while improving service performance. Therefore, developing high-performance and lightweight structural materials with high strength and high structural stability is crucial for the aerospace industry's technological advancements. In this study, the crystal structure, microstructure, and mechanical performance evolution of TiVZr–Nbx alloys (x = 0, 10, 15, 20, and 25 at%) were analyzed to investigate the transformation from an equimolar ternary alloy to a quaternary alloy. The density of the alloys increased from 5.8 to 6.5 g/cm3 when the crystal structure changed from the complex phases of the body-centered cubic (BCC) solid solution plus V-rich and Zr-rich phases to the BCC-dominated phase (98 %). The atomic radius difference δ for forming such a BCC-dominated phase must satisfy δ ≤ 6.1 %. The TiVZr–Nbx(x = 0, 10, 15 at%) alloys comprised coarse grains with lots of inclusions at the grain boundaries or inside the grains. The inclusions are eutectoid agglomerate of BCC-V(s) and HCP-Zr(s), which improved the room-temperature tensile strength while decreasing plasticity. Tensile strength increased with increasing Nb content at high temperatures, and the equimolar TiVZrNb alloy exhibited the highest resistance to softening, although its strength rapidly decreased below 150 MPa at 800 °C. We observed precipitates of the hcp-Zr phase beginning at approximately 400 °C when the high-temperature thermal stability of the TiVZrNb alloy was investigated. This caused less disorder in the multi-principal solid solution and weakening of the atomic bonding force, resulting in low tensile strength at 800 °C. This study provides the foundation for understanding the high-temperature thermal stability of refractory high-entropy alloys and their failure mechanisms. ● Lightweight TiVZr-Nbx multi-component alloys with density from 5.8 to 6.5 g/cm3 were produced by arc melting. ● As the Nb increases, the eutectic precipitates of V and Zr was suppressed and a BCC dominated structure formed. ● The atomic radius difference for forming a BCC-dominated (98%) phase must satisfy. ● Tensile strength increased with increasing Nb at high temperatures. ● Massive precipitation of Zr beginning at about 400 ℃ leads TiVZrNb alloy unstable at high temperatures. [ABSTRACT FROM AUTHOR]

Upgrading and developing metallic materials are bases for improving the performance of aircraft. As one of the new structural metallic materials used in aerospace, lightweight and high-strength γ-TiAl alloys have been successfully used as high-risk structural parts in aircraft engines. Nonetheless, intrinsic embrittlement is the main factor limiting applications of γ-TiAl alloys. To further enlarge the application fields of γ-TiAl alloys, it is urgent to improve mechanical properties, like strength and ductility. This paper first introduces phase constituents and precipitates of γ-TiAl alloys, summarizes microstructure control measures of γ-TiAl alloys, and presents texture evolutions of γ-TiAl alloys. Then, based on four strength mechanisms, this review paper summarizes factors influencing mechanical properties of γ-TiAl alloys during compression, tension, creep and fatigue as well as tribology tests. It also includes the fracture mechanisms of γ-TiAl alloys. Finally, this paper proposes some future development directions for studying γ-TiAl alloys, like screening chemical compositions via machine learning technology, and developing microstructure evaluation software. [Display omitted] [ABSTRACT FROM AUTHOR]

• A two-directional Cf/Al composite with a thermal conductivity of 305.5 W∙m−1∙K−1 is fabricated. • The CF MP acts as fast heat conduction channels. A two directional high thermal conductive carbon fiber reinforced aluminum matrix composite with low interface damage is prepared by a vacuum hot-pressure diffusion method using the mesophase-pitch-based carbon fiber (CF MP) cloth as fast heat conduction channels. The fiber/matrix interface is composed of an amorphous gradient transition layer between aluminum matrix and CF MP rather than Al 4 C 3 interface phase, thus endowing the continuous heat conduction channels in the composite. The composites deliver the high thermal conductivity of 305.5 W∙m−1∙K−1 in the X (Y) direction and the low volume density of only 2.53 g∙cm−3 when the fiber volume fraction reaches 30 vol%. The high thermal conductivity of the composite is attributed to the highly oriented fast heat transfer effect of the CF MP , the isotropic heat transfer effect of the aluminum matrix and the low-damage CF MP /aluminum interface. This study opens a new avenue to design and select the high thermal conductivity and lightweight thermal management materials for the aerospace field. [ABSTRACT FROM AUTHOR]

There is a keen interest in developing discontinuously reinforced titanium matrix composites (DRTMCs) as lightweight structural materials for aerospace and automotive industries. However, a long-standing problem for these materials is the conflict between strength and ductility. To address this challenge, a novel Ti-Mo-Si composite with network microstructure is successfully fabricated by spark plasma sintering and hot rolled in the β region (900 °C) with different statin rate. We find that a thickness reduction of 20% is optimal for improving the strengthening efficiency and corresponding ductility. However, with the reduction of thickness in the hot rolling process, the strength increases while the ductility decreases, which is mainly because of the spheriodiation of α-Ti and reinforcements, as well as the strengthening of the interface between reinforcement and matrix. In addition, the composite after hot rolling follows fractured reinforcement and dimple mechanisms at small thickness reduction, while it obeys a quasi-cleavage fracture mechanism with significant thickness reduction. • Deformation behaviours of (Ti 5 Si 3 +TiC)/Ti-Mo-Nb-Al composite with Network structured were investigated. • With increase of rolling thickness, the lamellar a and irregular reinforcements become increasingly spheroidizing. • The relationship between microstructure of reinforcements and residual stress was established via FE. • The strength contribution from the involved strengthening mechanisms was discussed. [ABSTRACT FROM AUTHOR]

• The SiC nanowires (SiC nw) were prepared and successfully tuned the interphase of the SiC f /SiC nw /Si 3 N 4 composites. • The introduction of SiC nw made the flexural strength of the SiC f /SiC nw /Si 3 N 4 composite improve to 333 ± 29 MPa. • The SiC nw interphase enhanced the dielectric loss of the composite, achieving a RC min of −51.4 dB. The interphase of composites is a vital element in controlling the overall performance. Herein, the SiC nanowires (SiC nw) were grown on the interface of the SiC fiber (SiC f)/Si 3 N 4 composites and successfully achieved the integration of enhanced mechanical and electromagnetic wave (EMW) absorption performance. The introduction of SiC nw made the bonding between the SiC f and Si 3 N 4 matrix more appropriate, thereby enhancing the mechanical properties. The defects, stacking faults, twin boundaries and heterogeneous interfaces in SiC nw improved the dielectric loss of the composites, which was beneficial to the consumption of EMW energy. Notably, the SiC f /SiC nw /Si 3 N 4 composite containing 1.8 vol% SiC nw demonstrated the optimal mechanical and EMW absorption properties, reaching a flexural strength of 333 ± 29 MPa, a minimum reflection coefficient (RC min) value of − 51.4 dB with a thickness of 3.2 mm and an effective absorption bandwidth (EAB) of 3.5 GHz with a thickness of 2.8 mm. Besides, the fracture mechanism and EMW absorption mechanism are also discussed. This work provides a potential new way to prepare lightweight, stable, and high-performance EMW absorbing materials for aviation and aerospace. [ABSTRACT FROM AUTHOR]

Al-Zn-Mg-Cu alloy, as an important lightweight structural material in the aerospace field, has ushered in a broader application space and proposed higher performance requirements. This paper presents the experimental investigation of the effect of Zr content on the microstructure refinement and performance improvement of cast Al-5.8Zn-2.3Mg-1.7Cu alloy, aiming to optimize the additional amount of Zr, refine the alloy grains, and improve the microstructure uniformity and mechanical properties. The chemical component, phase, and microstructure were observed by inductively coupled plasma, X-ray diffraction, optical microscope and scanning electron microscope; the hardness and mechanical properties were measured by Brinell hardness tester and tensile testing machine. The addition of different contents of Zr into the alloy can form fine dispersed or primary coarse Al 3 Zr phase, which has a significant effect on the microstructure and mechanical properties of the alloy. The results indicate that the addition of 0.05 wt% Zr does not significantly improve the grain refinement and mechanical properties, but the Brinell hardness reaches the maximum. As the Zr content rises, the grain refinement effect becomes more obvious, while the mechanical properties first increase and then decrease. The addition amount reaches 0.20 wt%, the second dendrite arm spacing is the smallest, the ultimate tensile strength, yield strength and elongation at room temperature reach the maximum of 296.74 MPa, 249.41 MPa and 8.26%, respectively. When the amount of Zr added exceeds 0.20 wt%, the existence of coarse and brittle primary Al 3 Zr phase reduces the mechanical properties, and the fracture morphology changes from ductile to brittle intergranular fracture. • Zr element can refine the alloy grains. The higher the amount of Zr added, the more obvious the grain refining effect. • With the increase of Zr content, the mechanical properties of the alloy will first increase and then decrease. • When Zr content is excessive, the Al 3 Zr phase is the reason for the decrease in toughness. [ABSTRACT FROM AUTHOR]

• Laser-deposition technique was employed for the fabrication. • The influence of laser process parameters on the corrosion resistance was investigated. • The scanning speed had more influence on corrosion behaviour than the laser power. • The Ti-based HEAs was more resistant to corrosion than the Cu-based HEAs. Corrosion is a conservational occurrence that has a large economic impact on most metals and its alloys because it destroys and deteriorates most materials by an electrochemical process through the reaction of these materials with the environment. High Entropy Alloys in aerospace applications react with the environment in applications such as jet engines, especially at elevated temperatures. Thus, the capacity of high entropy alloys to resist corrosion must be investigated to expand the application of this advanced material in the aerospace industry. In this comparative study, AlCoCrFeNiCu and AlCoCrFeNiTi High Entropy Alloy samples were fabricated by Laser Additive Manufacturing, particularly direct energy deposition and the corrosion behaviour of both alloys were examined and compared. The influence of the laser processing parameters on the microstructure and corrosion responses of the high entropy alloys in 3.5 wt% NaCl solution was also investigated. The microstructural morphologies were examined using an X-ray diffraction system (XRD) and Scanning electron microscope (SEM) equipped with Energy Dispersion Spectroscopy (EDS). The results showed that the Scan speed had the most influence on the microstructure and corrosion behaviour of the alloys. There was a strong relationship between the phase structure of the alloys and their susceptibility to localized corrosion. Therefore, it has been proposed in this study that the phase distribution within the alloys also influences the corrosion behaviour of laser deposited high entropy alloys. [ABSTRACT FROM AUTHOR]

C/C–ZrC–SiC–ZrB 2 composites were prepared by a joint process of precursor infiltration and pyrolysis and slurry infiltration. The high-temperature mechanical properties of the composites were reported and the evolution of fracture behavior and microstructure was analyzed. The composites exhibited a tensile strength and flexural strength of 99.3 MPa and 281 MPa, respectively during the test at ambient temperature. The high temperature in-situ tensile properties were higher than those at ambient temperature; the tensile strength was 136 MPa during the tensile test at 1700 °C. This is because the energy absorption mechanisms will occurred during the high-temperature test. The high temperature in-situ flexural strength was 223 MPa during flexural test at 1800 °C. However, the flexural strength of as-prepared composites after heat treat at 1800 °C was maintained at 153 MPa, which was lower than that of the in-situ flexural test at 1800 °C, because the fibers were more seriously eroded after heat treatment at 1800 °C. After heat treatment at 2400 °C, the flexural strength of the composites decreased to 88 MPa. It can be inferred that the high temperature in-situ flexural strength at 2400 °C was higher than 88 MPa, showing outstanding ultra-high temperature mechanical properties. Therefore, the C/C–ZrC–SiC–ZrB 2 composites are promising to be applied as structural material in aerospace, due to their excellent high-temperature mechanial properties at 1500 °C–2400 °C. • The composites were prepared by a joint process of PIP and slurry infiltration. • The composites exhibited a tensile strength and flexural strength of 99.3 MPa and 281 MPa at RT. • The in-situ tensile strength was 136 MPa at 1700 °C. • After heat treatment at 2400 °C, the flexural strength decreased to 88 MPa. [ABSTRACT FROM AUTHOR]