Grain Growth Research Articles

Modulating secondary growth of perovskite grains through residual solvent evaporation

Over the past decade, perovskite solar cells (PSCs) have attracted enormous attention due to their high performance. One key to fabricating high-quality perovskite films lies in controlling the volatilization rate of residual solvents during the annealing process. This study systematically investigates how different protective substrates affect the volatilization rate of residual solvent in perovskite films. By adjusting the direction and rate of evaporation, the supersaturation time of the solution was precisely controlled, leading to effective recrystallization of the grains. Concurrently, the annealing time was optimized to enhance film quality further. This optimization aimed to increase crystallinity, reduce defects, and thereby minimize non-radiative recombination centers. Implementing these methodologies, particularly the use of filter paper as a protective substrate during a 2-minute annealing process, significantly improved the fill factor (FF) and open-circuit voltage (VOC) of the PSCs. This led to a remarkable 5.26% improvement in power conversion efficiency (PCE) compared to control devices. The strategies employed in this work demonstrate significant potential in improving PSC film quality. This approach not only advances our understanding of film formation dynamics but also provides a practical guideline for future PSC fabrication.

Obtaining extremely low coercivity of high Bs FeCoBSiCPCu nanocrystalline alloys through modulation of magnetic anisotropy

Longitudinal magnetic field annealing is utilized for modifying the magnetic anisotropy and enhancing the magnetic softness of Fe75Co8(B10Si3C3P1)1-x/17Cux (x = 0.5, 0.75, 1, 1.25) nanocrystalline alloys. All of the magnetic field-annealed nanocrystalline alloys with Cu content more than 0.5 at.% exhibit significantly improved soft-magnetic properties, including high saturation magnetic flux density up to 1.87 T, effective permeability of 13,000–16,000 under the condition of 1 A/m and 1 kHz, coercivity as low as 1.6 A/m, and core loss of 0.11–0.45 W/kg under the condition of 1.0 T and 50 Hz. The application of a magnetic field promotes the nucleation and inhibits the growth of grains, leading to an increase in the number density of nanocrystals and the crystalline volume fraction, and a reduction in the grain size. The magnetic field annealing reduces the effective magneto-crystalline anisotropy energy to 2–4 J/m3, and induces longitudinal magnetic anisotropy with anisotropy energy density of 400–900 J/m3 which shows dependence on the crystalline volume fraction. The field-induced magnetic anisotropy dominates over the random local magnetic anisotropies, and results in the formation of regular magnetic domains aligned longitudinally, pinning-free domain wall displacement, and thus enhanced soft-magnetic properties.

Segregation effects of doped VN and ZrN on magnetic and microstructural characteristics of FePt-based films

Segregants are essential materials for forming the complexation or granular microstructure in thin films for magnetic recording media. One such film, FePt-BN, has a metallic L10 FePt main phase as its matrix, in addition to having BN and C segregants at the grain boundaries. Amorphous BN has sufficient mechanical strength to support the columnar growth of FePt grains, however, it has a lower deposition rate resulting in columnar grains with a nonuniform aspect ratio. Moreover, some B diffuses in the interstitial site of FePt lattices. To overcome these limitations, this study added the transition nitride VN and ZrN with equal volume percentages to replace some BN segregants in FePt(BN, Ag, C) films: substantially different segregation behaviors were observed. Microstructural imaging mapping revealed that although VN segregated the FePt grains boundary, ZrN was diffused in the lattice. The FePt-BN-ZrN film thus had more disordered grains contributing to a higher in-plane magnetization and wider hard axis magnetic hysteresis loops than did FePt-BN-VN. The FePt-BN-VN film has the highest perpendicular magnetic anisotropy constant (Ku= 2.17 × 106 J/m3) and coercivity (Hc= 4 T); moreover, parallel remanence magnetization was minimal with a linear in-plane magnetization loop. The FePt-BN-VN film was sputtered directly on MgO(100) but depositing the FePt-BN-ZrN film required a 2-nm-thick FePt nucleation layer. The high atomic number of Zr and high sputter yield ratio (YN/Ymetal) of ZrN may increase the sites occupied by N, potentially affecting ZrN segregation.

Effect of preparation conditions on the surface morphology and edge absorption of ZnGa2O4:Cr thin films

Thin ZnGa2O4:Cr films were obtained by RF ion-plasma sputtering in argon and argon-oxygen atmospheres mixtures on single-crystal NaCl and amorphous υ-SiO2 substrates. The surface morphology of the films was studied by atomic force microscopy. It was found that during the annealing of ZnGa2O4:Cr films on υ-SiO2 substrates in oxygen, the grains forming the film grow along the film surface, and during annealing in an argon atmosphere, the growth of grains is observed normal to the film surface. The region of the fundamental absorption edge was studied by optical spectroscopy. The variation of the optical band gap of Eg depending on the deposition and annealing atmosphere was determined. The total effective mass of free charge carriers and the concentration of free charge carriers are estimated. It is shown that the shift of the fundamental absorption edge in ZnGa2O4:Cr thin films after annealing in an argon atmosphere and when oxygen is added to the sputtering atmosphere is due to the Burstein-Moss effect.

Terpinen-4-ol from tea tree oil prevents Aspergillus flavus growth in postharvest wheat grain

Plant volatile organic compounds (PVOCs) have gained increasing attention for their role in preventing fungal spoilage and insect contamination in postharvest agro-products owing to their effectiveness and sustainability. In this study, the essential oil was extracted from fresh M. alternifolia (tea tree) leaves, and the fumigation vapor of tea tree oil (TTO) completely inhibited the growth of Aspergillus flavus on agar plates at a concentration of 1.714 μL/mL. Terpinen-4-ol was identified as the major component (40.76 %) of TTO volatiles analyzed using headspace gas chromatography–mass spectrometry. Terpinen-4-ol vapor completely inhibited the A. flavus growth on agar plates and 20 % moisture wheat grain at 0.556 and 1.579 μL/mL, respectively, indicating that terpinen-4-ol serves as the main antifungal constituent in TTO volatiles. The minimum inhibitory concentration of terpinen-4-ol in liquid-contact culture was 1.6 μL/mL. Terpinen-4-ol treatment caused depressed, wrinkled, and punctured mycelial morphology and destroyed the plasma membrane integrity of A. flavus. Metabolomics analysis identified significant alterations in 93 metabolites, with 79 upregulated and 14 downregulated in A. flavus mycelia exposed to 1.6 μL/mL terpinen-4-ol for 6 h, involved in multiple cellular processes including cell membrane permeability and integrity, the ABC transport system, pentose phosphate pathway, and the tricarboxylic acid cycle. Biochemical analysis and 2,7-dichlorofluorescein diacetate staining showed that terpinen-4-ol induced oxidative stress and mitochondrial dysfunction in A. flavus mycelia. This study provides new insights into the antifungal effects of the main TTO volatile compounds terpinen-4-ol on the growth of A. flavus.

Pea growth, yield, and quality affected by nitrogen fertilization to previous crop in small grain–pea rotations

AbstractStarter N fertilization at low rates may enhance pea (Pisum sativum L.) performance, but little information exists about the effect of N fertilization rate to previous crop (NRPC) on pea growth, yield, and quality in small grain–pea rotations. We examined the effect of N fertilization rates to barley (Hordeum vulgare L.) and spring wheat (Triticum aestivum L.) on succeeding pea growth, yield, and quality in barley–pea and spring wheat–pea rotations from 2006 to 2019 in the semiarid environment of US northern Great Plains. We measured pea plant density, straw and grain yields, harvest index, straw N concentration, grain protein concentration, grain test weight, straw and grain N uptake, and N harvest index. In the barley–pea rotation, pea grain yield increased with increased NRPC. Grain test weight was greater without than with NRPC in 2008 and 2009. In the spring wheat–pea rotation, straw yield was greater for 50 than 0 kg N ha−1 of NRPC in 2014, 2018, and 2019. Grain yield and N uptake were greater with than without NRPC in 2014, 2015, and 2019, but grain test weight varied with NRPC and year. Plant density, harvest index, straw N concentration, grain protein concentration, straw N uptake, and N harvest index varied with year in both barley–pea and spring wheat–pea rotations. Nitrogen fertilization to barley or spring wheat can enhance succeeding pea grain yield and N uptake during years with normal growing season precipitation in barley–pea and spring–wheat pea rotations in the semiarid region of the US northern Great Plains.

Interfacial modulation of SiC/TiC hybrid nanofibers for fabricating flexible ceramic electromagnetic wave absorbers

Titanium Carbide (TiC), characterized by its hardness, conductivity and thermal stability, can serve as a suitable additive phase for SiC nanofibers. TiC phase can improve the flexibility and electromagnetic wave absorption property of SiC nanofibers without sacrificing its high-temperature thermal stability. Herein, flexible SiC/TiC hybrid nanofibers with different Ti contents were fabricated by electrospinning and precursor infiltration pyrolysis. The introduction of Ti can not only generate conductive TiC phase, but also act as a catalyst to regulate the growth of SiC grains, so as to adjust the flexibility and electromagnetic properties of the hybrid nanofibers. At the optimal Ti precursor content of 4 wt%, the SiC/TiC-4 hybrid nanofibers exhibit a broad effective absorption bandwidth of 4.5 GHz with the thickness of 1.6 mm. The flexible SiC/TiC hybrid nanofibers This work can provide a reference for the design of flexible ceramic nanofiber absorbers and is expected to enable practical application in high temperature conditions.

The nucleation and growth of fine austenitic grain at interface of the L415QS/N08825 bimetallic composite pipe by explosive welding

The nucleation and growth of fine austenitic grain at interface of L415QS/N08825 bimetallic composite pipe achieved by explosive welding is systematically studied. Results show that the L415QS/N08825 interface have heat affected zone (HAZ) that is similar with GH2132 superalloy (Fe-25Ni-15Cr). Two kinds of austenitic grains: columnar grains and ultra-fine equiaxed grain with large angle grain boundaries were identified at HAZ that nucleated from both L415QS and N08825 base alloy in the melts zone, and the growth of the nucleus is based on the size of melts zone. Room temperature nanoindetation test revealed that these fine equiaxed and columnar austenitic grains exhibit enhanced hardness compared with those of the base metals.

Unexpected texture transition induced by grain growth during static annealing of a dilute Mg-1Al alloy

Conventional rolled Mg-Al alloy sheets typically exhibit strong basal textures that remain and may even strengthen after recrystallization annealing due to the preferential growth of basal-oriented grains, resulting in poor formability at room temperature. Therefore, the knowledge of recrystallization and grain growth is critical for modifying textures of Mg-Al alloy sheets. The static recrystallization and texture evolution in a cold-rolled dilute Mg-1Al (wt.%) alloy during various annealed temperatures ranging from 300 °C to 450 °C, have been investigated using the quasi in-situ electron backscatter diffraction (EBSD) method. The as-rolled Mg-1Al alloy shows a dominant basal texture, which weakens and broadens in the rolling direction (RD) during the subsequent annealing, accompanied by the formation of 〈101¯0〉 texture component. Particularly, the 〈101¯0〉 texture component is more pronounced after annealing at high temperatures. The quasi in-situ EBSD results show that recrystallized grains are mainly induced by shear bands, which exhibit a wide spectrum of orientations with c-axis tilt angles ranging 20°-45° from the normal direction (ND). Orientations of shear band-induced recrystallized grains are retained during the entire recrystallization process, resulting in a reduction in the texture intensity. Moreover, recrystallized grains belonging to the 〈101¯0〉 texture component grow preferentially compared to those with other orientations, which is attributed to low energy grain boundaries, especially grain boundaries with ∼30° misorientation angles. Furthermore, the high temperature annealing facilitates the rapid growth of grain boundaries having a 30° misorientation angle, leading to the occurrence of distinct 〈101¯0〉 texture after annealing at 450 °C for 1 h. The results provide insights for texture modification of rare earth-free low-alloyed Mg alloys by controlling annealing parameters.

Improved electrical transport properties of La0.7Ca0.3−xKxMnO3 (0.0 ≤ x ≤ 0.3) films grown on La0.3Sr0.7Al0.65Ta0.35O3 (00l) substrates by sol–gel spin coating method

Herein, La0.7Ca0.3−xKxMnO3 (LCKMO) films with highly oriented growth were prepared on La0.3Sr0.7Al0.65Ta0.35O3 (00l) substrates by sol–gel spin coating method. Comprehensive analysis of microstructure, surface morphology, ion valence, and electrical transport properties of LCKMO films indicates that the substitution of K+ ions for Ca2+ ions increased the ratio of Mn4+/(Mn3+ + Mn4+), narrowed the one electron bandwidth, and enhanced double exchange mechanism and electron–lattice coupling. Moreover, the doping of K+ ions induced the dense and uniform conical-structured growth of grains on the surface of the films. Results demonstrated that at x = 0.1, LCKMO film exhibited the maximum TCR of 17.84% K−1 at 253.07 K, which was 31.76% higher than that of previously reported La1−x−yCaxKyMnO3 ceramic with the highest TCR. Further theoretical insights into the effects of Ca/K co-doping on electrical transport properties were supplemented.

Microstructure evolution of ATI718 plus alloy during high-speed machining: Experiments and a combined FE-CA approach

Excellent surface integrity is an eternal pursuit in high performance manufacturing, with microstructure being a crucial component of the surface integrity dataset and a key factor controlling surface properties such as fatigue and creep. The multi-physical fields generated by thermo-mechanical loads during high-speed machining act on the processed surface layer, influencing the evolution of microstructures. To investigate the microstructural evolution mechanisms of ATI718 plus during high-speed machining, cutting experiments and techniques such as Electron back scatter diffraction (EBSD), Transmission Kikuchi diffraction (TKD), and Precession electron diffraction (PED) is conducted to quantitatively analyze the microstructures in the chip shear zone and the machined surface. Subsequently, a combined finite element (FE) and cellular automata (CA) model is developed to simulate the microstructure evolution during the cutting process. The discontinuous dynamic recrystallization (DDRX) mechanism is employed to demonstrate the nucleation and growth of grains under the influence of multiple physical fields. The simulation and experimental results show similar dynamic recrystallization (DRX) grain sizes, indicating acceptable accuracy of the CA model in terms of DRX grain size. The comparison between experimental and simulation results confirms the occurrence of both continuous dynamic recrystallization (CDRX) and DDRX during the cutting process. The synergistic competition between CDRX induced grain lamellar refinement and DDRX induced grain growth emerge as the primary mechanism driving microstructural evolution. A layer of ultrafine grains, with a thickness within 20 μm, is formed on the machined surface. Results under different parameters demonstrate that the temperature has a more significant impact on the thickness of the ultrafine grain layer and the diameter of grains within the layer compared to the strain rate.

Investigation of Cu-Sn-Sb Thin Film for Ultra-Speed and Phase High-Reliability Change Memory Applications

SnSb (SS), a vital phase-change thin film, has attracted attention due to its excellent phase-change properties, but the poor amorphous stability and crystalline speed of SS greatly limit its application in rapid phase-transition memories. Here, we propose a copper (Cu)-doped SS phase change films to achieve ultra-speed and high-reliability of SS. Resistance-temperature tests show Cu-Sn-Sb possesses ultra-low crystalline and amorphous resistivity, higher phase transition speed, and lower activation energy. X-ray diffraction measurements illustrate the introduction of Cu ions hinders the growth of grains and reduce grains size. Atomic force microscopy characterizes the surface morphology of as-deposited and annealed Cu-Sn-Sb films, and difference of root-mean-square roughness before and after annealing promote Cu-Sn-Sb film is more reliable to touch electrodes. In addition, the ultra-low resistivity and fast transition speed effectively reduce thermal loss in SET and RESET process. The results reveal that Cu-Sn-Sb is a promising material for ultra-rapid phase change and high-reliability storage applications.

Effect of graphene and niobium carbide on microstructure and mechanical properties of Ni60 composite coatings prepared by laser cladding

Niobium carbide (NbC) is often used as a reinforcing phase to improve the mechanical properties of composite coatings, but its low thermal conductivity makes the flow of molten pool poor, and the cladding layer is prone to defects such as non-fusion and slag inclusion. Therefore, in this paper, Ni60–NbC composite coatings with different NbC content were prepared by laser cladding technology, and the 10 vol% graphene-20 vol% NbC-70 vol% Ni60 composite coatings were prepared under the optimal NbC component. The effects of the addition of NbC and graphene on the microstructure and microhardness of the coating were systematically discussed. The results show that the microhardness of 20 vol% NbC composite coating is increased from 680.1 HV to 882.9 HV compared with Ni60 coating without NbC.The composite coating with both NbC and graphene has a microhardness of up to 1048HV, which is 18% higher than the composite coating with only 20 vol% NbC. The mechanism is that the addition of graphene promotes the formation of chromium carbide (Cr23C6, Cr7C3) and increases the fluidity of the molten pool, which causes small niobium carbide particles to dissolve and recondense to form large particles. Large niobium carbide particles and chromium carbide jointly inhibit the excessive growth of other grains. This study provides a new idea for laser cladding of nickel-based composite coatings.

Strip Casting of Sm2TM17-Type Alloys for Production of the Metastable SmTM7 Phase

Conventional book casting of Sm2TM17-type alloys (where TM = Co, Fe, Cu, Zr) leads to a coarse, highly segregated microstructure, predominantly due to the slow, variable cooling rate from the mould surface towards the centre of the ingot. These cast alloys require a long homogenisation treatment to remove this segregation and develop a super-saturated, metastable SmTM7-type hexagonal phase. This SmTM7 phase is a vital precursor phase required during magnet production to develop the complex cellular structure responsible for high magnetic properties. In this work, strip casting was employed to facilitate rapid solidification to develop thin flakes (<0.5 mm thick) with a columnar grain structure. Rapid cooling has the potential to produce a homogenous microstructure consisting predominantly of the metastable SmTM7 phase. This could remove or significantly reduce the need for the energy-intensive homogenisation treatment usually required in conventional magnet manufacture. This paper investigates the effect of wheel speed (and hence cooling rate) on flake thickness, microstructure, and phase balance of the cast alloys. It was shown that for wheel speeds between 1.1 and 3.0 m/s, the microstructure showed large variation; however, in all cases, evidence of the columnar SmTM7 phase was presented. The adhesion between the melt and the wheel was deemed to be critical for the nucleation and subsequent columnar growth of SmTM7 grains, where the wheel speed controlled both the flow of the alloy onto the wheel and the thickness of the resultant flake. It was determined that in order to achieve a homogenous columnar SmTM7 structure, the maximum flake thickness should be limited to 270 μm to avoid the formation of equiaxed Sm2TM17 grains through insufficient cooling.

Microstructure and Mechanical Properties of a New TWIP Steel under Different Heat Treatments.

The effects of solution treatment and annealing temperature on the microstructure and mechanical properties of a new TWIP steel that was alloyed from aluminum (Al), silicon (Si), vanadium (V), and molybdenum (Mo) elements were investigated by a variety of techniques such as microstructural characterization and room tensile testing. The austenite grain size grew slowly with the increase in annealing temperature. The relatively weak effect of the solution treatment and annealing temperature on the austenite grain size was attributed to the precipitation of MC and M2C, which hindered the growth of the austenite grain. The plasticity of the TWIP steel in cold rolling and annealing after solution treatment was obviously higher than that in cold rolling and annealing without solution treatment. This was because the large-size precipitates redissolved in the matrix after solution treatment, which were not retained in the subsequently annealed structure. Through cold rolling and annealing at 800 °C after solution treatment, the prepared steel exhibited excellent strength and plasticity simultaneously, with a yield strength of 877 MPa, a tensile strength of 1457 MPa, and an elongation of 46.1%. The strength improvement of the designed TWIP steel was mainly attributed to the grain refinement and precipitation strengthening.

Tuning heterogeneous microstructure and improving mechanical properties of twin-roll strip cast low carbon steels by on-line heat treatments

Coarse austenite grains are unavoidable in the low carbon steels processed by twin-roll strip casting. Unfortunately, the polygonal ferrite (PF) grains cannot be refined by conventional on-line cooling process, resulting in low strength. In this work, an on-line heat treatment including reaustenitizing and subsequent controlled cooling was performed in laboratory to form heterogeneous microstructures composed of PF and acicular ferrite (AF). It has been founded that increased prior austenite grain size and the cooling rate led to more AF laths, which inhibited the growth of PF grains. When the prior austenite grain size is less than 60 μm, the formation of AF is suppressed. The tensile tests indicate that the heterostructured steels exhibited higher yield strength than the samples without AF. The improvement of yield strength can be attributed to the grain boundary strengthening, dislocation strengthening and back stress strengthening. The higher AF volume fraction leads to higher dislocation density in PF grains, and more AF/PF interfaces may increase the amount of accumulated geometrically necessary dislocations. Therefore, the contributions of dislocation and back stress strengthening increase with the increase of AF volume fractions. High dislocation density and the generation of back stress contribute a high strain hardening rate to delay the necking and sustain good plasticity. Moreover, the heterostructured steels exhibit the two-stage work hardening behavior during tensile test, which indicates that plastic deformation starts in PF grains while the AF laths remain in elastic state, and then plastic deformation occurs in both strain hardened PF grains and AF laths.

Small Molecule Regulatory Strategy for Inorganic Perovskite Solar Cells with 368 mV of VOC Deficit and its Application in Tandem Devices

AbstractTandem solar cells combining perovskite and silicon have witnessed rapid development in recent years. However, the top cell, utilizing wide‐bandgap perovskite as absorbers generally suffer significant open‐circuit voltage (VOC) deficit, particularly for inorganic perovskite, which poses a considerable obstacle to enhancing the power conversion efficiency (PCE). Here, a modulation strategy by using 2,6‐pyridinedicarboxamide (PC), the crystallization kinetics of inorganic perovskite film can be effectively regulated, specifically manifested as a relatively longer annealing time in the air, resulting in sufficient growth for the inorganic perovskite grains. Additionally, PC can effectively in situ passivate uncoordinated Pb2+, suppressing the non‐radiative recombination of charge carriers. Eventually, a record PCE of 22.07% is achieved based on n–i–p inorganic perovskite solar cells (IPSCs), which also demonstrate the highest VOC above 1.34 V (1.71 eV of bandgap). More importantly, the unencapsulated IPSCs show enhanced thermal stability and photostability. Furthermore, the n–i–p IPSCs are also applied to inorganic perovskite/silicon tandem solar cells (IPTSCs), a PCE of 27.27% and an impressive VOC of 2.024 V are obtained.

Effect of annealing temperature on the evolution of microstructure, texture, and mechanical properties of hot-rolled 12Cr-ODS steel

To achieve high thermal efficiency, today's nuclear reactor structures are exposed to higher temperatures and pressures, which requires the use of high-strength steels with specific properties, such as ODS steels. There is a need to clarify the evolution of the microstructure and properties of steels at elevated temperatures. This study systematically investigates the evolution of microstructure, texture, and mechanical property variations of 12Cr-ODS steels after hot-rolling and subsequent annealing at 1000 °C and 1200 °C. The investigation utilizes optical microscopy, electron backscatter diffraction technique, and mechanical property measurements. The microstructure of hot-rolled samples shows a layered alternating distribution, which is distinguished by a notable presence of the α-fiber texture. Following annealing at 1000 °C, the martensite grains are smaller with a reduced hardness, while maintaining a strong α-fiber texture. After annealing at 1200 °C, there is a rapid increase in the growth of martensite grains, a significant rise in hardness, a reduction in the α-fiber texture characteristics, and an improvement in the γ-fiber texture characteristics. Moreover, the maximum intensity of the α-fiber texture diminishes as the annealing temperature increases. The mechanical properties of the samples deteriorated after annealing at 1200 °C, which can be attributed to the coarse martensite grains and the texture components containing the {001} cleavage plane dominating the occurrence of brittle cleavage fracture. The 0.1Y sample after annealing at 1000 °C exhibits an excellent combination of strength (1458 MPa) and ductility (20.3%), which is owing to the unique heterogeneous grain structure and the evolution of favorable texture.

Effects of Al2O3 and Cr2O3 on the microstructure and properties of Mo alloys prepared via vacuum sintering

The dilemma of strength and ductility of Mo alloy at ultra-high temperature (above 1300 °C) limits its application in space reactors and other high-temperature environments. Single oxide enhancement has been unable to meet these use requirements. In this research, a strategy of synergistic reinforcement of Mo alloys with nanosized Al2O3 and Cr2O3 ceramic particles was proposed. A 300−400 nm Mo alloy powder was prepared by liquid‒solid doping, and in situ self-generated nanosized oxides were obtained. The grain size of vacuum sintered Mo alloy was very fine, at only 5.3 μm, which was one tenth of the particle size of commercial Mo alloy. Al2O3 and Cr2O3 particles were distributed in the grains of the Mo matrix, which effectively prevented the growth of Mo grains during vacuum sintering and reinforced the Mo alloy. The maximum flow stress of the Mo–Al2O3–Cr2O3 alloy reached 367 MPa at 1000 °C/1 s−1, which was better than that of the single-oxide reinforcement. The ultimate tensile strength (UTS) of the Mo–Al2O3–Cr2O3 alloy was 862 MPa, which was twice that of pure Mo. The preparation process is simple and available for industrial production. Synergistic strengthening of multiple oxides will be the best strategy for strengthening refractory alloys in the future.

Tailoring properties of directed energy deposited Al-Mg alloy by balancing laser shock peening and heat treatment

Wire arc-directed energy deposition (WADED) has shown great advantages and potential in fabricating large-scale aluminum (Al) alloy components. However, WADED Al alloys typically exhibit low strength and reliability due to pore defects and lack of work hardening or precipitation strengthening. This study utilized a combination of laser shock peening (LSP) and annealing to regulate the microstructure of WADED Al-Mg4.5Mn alloy and enhance mechanical properties. The effects of LSP and annealing on phase composition, pore distribution, and microstructures at multiple scales were systematically investigated to reveal the mechanical property improving mechanism. The results demonstrated that LSP-induced plastic deformation formed a defect-free zone by closing near-surface pore defects. LSP created the hardened layer with gradient mechanical properties by inducing gradient changes in grain size, the number of low-angle grain boundaries (LAGBs), and dislocation density along the depth direction. The annealing process promoted grain coarsening and reduced excessive dislocations and LAGBs, weakening the work hardening effect caused by LSP. Furthermore, the high-density dislocations and high stored energy generated by LSP accelerated the recrystallization, facilitating growth of near-surface grains. The defect-free zone, dislocation strengthening, and LAGBs strengthening were responsible for the increase in strength, while the synergistic deformation between hardened layers and soft core facilitated maintaining excellent elongation. The strength and elongation of WADED Al alloy can be synergistically improved by balancing the effects of LSP and heat treatment.