Two-step Annealing Research Articles

Deformation mechanism of a metastable medium entropy alloy strengthened by the synergy of heterostructure design and cryo-pre-straining

Face-centered cubic (FCC) medium entropy alloys (MEAs) have received considerable attention due to their impressive mechanical properties and responses. However, their practical application is limited by their modest yield strengths. The potential enhancement of the mechanical properties of single-phase MEAs was explored in this study through a synergistic approach combining heterogeneous structure design with subsequent cryo-pre-straining. A heterogeneous lamella structure was produced in a single-phase Fe55Mn20Cr15Ni10 MEA via two-step rolling and annealing. Cryo-pre-straining at varying degrees (6, 12, 21, and 36%) introduced hexagonal close-packed (HCP) phase, high-density dislocations, twins, and stacking faults, leveraging the reduced stacking fault energy at cryogenic temperatures. This process enhanced the alloy's yield strength from 353 MPa to 1.2 GPa (compared to the baseline uniform coarse-grained structure), while maintaining an acceptable total elongation of 8.4%. The impact of cryo-pre-straining on the microstructure and mechanical properties of the MEA was assessed using in-situ synchrotron X-ray diffraction analysis. Cryo-pre-straining (36%) achieved a higher dislocation density (6.1 × 1015 m−2) compared to room-temperature straining (2.5 × 1015 m−2). The stress contribution from HCP-martensite and the evolution of dislocation density during loading were quantified, along with observations of negative stacking fault probability and strain-induced HCP→FCC reverse transformation in cryo-pre-strained samples under loading conditions. Furthermore, the contributions of regulated microstructures to the enhancement of yield strength were quantitatively assessed.

N, S-Codoped 3D Carbon Protected Nanoporous MnS With Record High Sodium Ion Storage Performance for Potential Industry Applications.

With a high theoretical capacity, the MnS anode, however, exhibits a rather complex sodium diffusion kinetics and poor mechanical stability that hinder its application in sodium-ion batteries (SIBs). In this work, a simple, economical, and scalable strategy is developed to inherently coat nanoporous MnS with a 3D N, S co-doped thin carbon layer by using commercially available MnCO3 as precursors. Specifically, the strategy involves a two-step annealing process, which converts the MnCO3 microparticles into nanoporous Mn2O3 and MnS step by step. The 3D N, S codoped carbon layer is in situ formed during the second annealing process by first coating the nanoporous Mn2O3 with a polyaniline layer. Due to the inherent 3D carbon protection and the strong electronic interaction between N, S dopants and MnS, the N, S codoped carbon protected MnS obtained at 900 °C (NS-C@MnS-900) anode displays a high specific capacity of 845mAhg-1 at 0.1Ag-1, which is higher than all reported MnS-based SIB anodes. It also shows an outstanding cyclability and rate performance, maintaining a stable capacity of ≈493mAhg-1 after 1300 cycles at 10Ag-1, which is also the best according to knowledge. These exceptional electrochemical performances and the scalable/simple/low-cost synthesis make the NS-C@MnS-900 attractive for industry application.

Realization of grain growth and suppressed bulk defects for efficient solution-processed Cu2ZnSn (S, Se)4 solar cells via co-doping strategy

Environmentally benign and earth-abundant constituent’s kieserite Cu2ZnSn (S, Se)4 (Cotises) is considered as a hopeful photovoltaic material. Unfortunately, the severe tail state caused by various harmful deep defects in CZTSSe absorber prevents further development of its device efficiency. Here, we report firstly that the Co was incorporated into CZTSSe films to form the Cu2CoxZn1-xSn (S, Se)4 (CCZTSSe) films using a two-step annealing and solution-processing technique method. Through optimized the Co/(Co+Zn) ratio, the CCZTSSe film has excellent good surface morphology and single-phase composition. Appropriate amount of Co elements replacing Zn elements in CZTSSe films can effectively reduce the degree of Cu-Zn disorder, thus inhibiting [2CuZn+SnZn] defect clusters and CuZn defects. The detrimental deep defects located in the film were effectively passivated to reduce electrostatic potential fluctuations, resulting in relief of the trailing state. Therefore, a champion device having an efficiency of 7.50 % with a fill factor (FF) of 61.00 % was achieved from CCZTSSe with 3 % Co content. This work provides new insights into the impacts of Co doping in CZTSSe by a solution processed method and offers a deeper comprehension of the origin of the efficiency enhancement of CCZTSSe devices.

Oxygen precipitation behavior and its influence on phosphorus gettering in Czochralski silicon

This study investigates the effects of single-step and two-step annealing processes on the formation of oxygen precipitates and their impact on metal impurity gettering in gallium-doped monocrystalline silicon. The research focuses on the competitive relationship between internal gettering by oxygen precipitates and external gettering through phosphorus diffusion. Experimental results show that two-step annealing generates larger and more abundant oxygen precipitates, enhancing the internal gettering effect and reducing the recovery of minority carrier lifetime after phosphorus gettering. Despite this, phosphorus diffusion gettering remains effective in improving minority carrier lifetime, although the degree of improvement depends on the size and quantity of oxygen precipitates. These findings offer valuable insights for optimizing the fabrication process of silicon-based solar cells.

High-throughput exploration of the Na2O-ZrO2-SiO2-P2O5 composition space using thin film material libraries

AbstractThe composition space Na2O-ZrO2-SiO2-P2O5 was explored using thin film material libraries and high-throughput characterization methods. The combinatorial synthesis comprised non-reactive magnetron co-sputtering at room temperature from two elemental targets Zr and Si, and a compound Na3PO4 target followed by a two-step annealing process. The NASICON phase formed for all compositions on the material library produced at the optimized deposition parameters, also displaying a phase-pure Na1+xZr2SixP3−xO12 (x = 0.4—2.9) region. Analytical TEM analysis of the NASICON phase at a measurement area with stoichiometric composition revealed a fine-grained microstructure and homogeneous Si distribution, in contrast to Na-P excess conditions, where large Si-free NASICON grains have formed.

Degradation of phenol by metal-free electro-fenton using a carbonyl-modified activated carbon cathode: Promoting simultaneous H2O2 generation and activation

The low yield of hydrogen peroxide, narrow pH application range, and secondary pollution due to iron sludge precipitation are the major drawbacks of the electro-Fenton (EF) process. Metal-free electro-Fenton technology based on carbonaceous materials is a promising green pollutant degradation technology. Activated carbon cathodes enriched with carbonyl functional groups were prepared using a two-step annealing method for the degradation of phenol pollutants. The •OH in the activation process of H2O2 were identified using the EPR test technique. The action mechanism of carbonyl groups on H2O2 activation was investigated in conjunction with density functional theory (DFT) calculations. The EPR tests demonstrated that the modified activated carbon could promote the in-situ activation of H2O2 to •OH. And the results of material analysis and DFT showed that C=O could facilitate the activation of hydrogen peroxide through the electron transfer mechanism as an electron-donating group. Electrochemical tests showed that both the oxygen reduction activity and 2e−ORR selectivity of the modified activated carbons were significantly improved. Compared with the original activated carbon cathode and EF, the degradation efficiency of phenol in the ACNH-1000/GF cathode was increased by 58.10% and 45.61%, respectively. Compared with EF, ACNH-1000/GF metal-free electro-Fenton effectively expands the pH application range, and is proven to be less affected by solution initial pH, while avoiding secondary pollution. The metal-free electro-Fenton system can save more than a quarter of the cost of EF system. This study has a deep understanding of the reaction mechanism of the carbonyl modified activated carbon, and provides valuable insights for the design of metal-free catalysts, so as to promote its application in the degradation of organic pollutants.

Microstructure Evolution and Tensile Properties of Medium Manganese Steel Heat Treated by Two-Step Annealing

In this paper, the nucleation and growth of austenite are controlled through a two-step annealing process to achieve multi-scale distribution and content increase of retained austenite in low manganese series medium-Mn steel. Combining SEM, EBSD, AES, and other experimental equipment, the evolution rules of the microstructure, properties, and element distribution behavior of the test steel during the annealing process are studied. Compared with one-step annealing, the two-step annealing significantly broadens the size distribution range of retained austenite. In the first step, after annealing at a higher intercritical temperature (760 °C), the ferrite and the M/A island are obtained, completing the initial partition of Mn and the refinement of microstructures. During the second step of annealing (720 °C), the primary Mn-rich martensite region provides higher nucleation driving force and finer dispersed nucleation sites, promoting the nucleation and growth of reverse transformation austenite. At the same time, the metastable-retained austenite formed after the first step of annealing continues to grow through interface movement. Furthermore, a high proportion (23.4%) of retained austenite with multi-scale distribution is formed in the final microstructure, and the product of strength and elongation increased from 21.8 GPa·% by the one-step annealing process to 30.1 GPa·%.

Stability of retained austenite and its effect on tensile properties and hole expansion performance of high-strength steel

Medium manganese steel has a ferritic matrix with retained austenite as the secondary phase at room temperature (RT). The effect of the transformation-induced plasticity (TRIP) of retained austenite on steel has earlier been found to result in an excellent combination of high strength and ductility, making it a promising candidate as a third-generation advanced high-strength steel (AHSS) for automotive applications. Therefore, extensive research has recently been conducted with the aim to increase the amount of retained austenite in steel, thereby enhancing the strength and ductility of the steel. However, an increase in the amount of retained austenite can be detrimental to the HER, which is due to its low mechanical stability and the transformation to martensite when forming holes by punching. However, there has been relatively little research on this topic.The impact of the mechanical stability of retained austenite on the tensile properties and hole expansion ratio (HER) of high-strength medium-Mn steel have been investigated in the present study. Samples were prepared using one-step austenite-reverted-transformation (ART) annealing, which resulted in steel with 24.7 % retained austenite and moderate mechanical stability. The steel showed also an excellent combination of strength and ductility. Samples were also prepared using two-step annealing, which showed a positive effect on the HER of the steel, regardless of the processing method used for the formation of a central hole on the samples. However, it slightly reduced the ductility of the steel. For all these samples, the impact of the retained austenite on the HER was found to be closely related to its mechanical stability and content in the steel.Retained austenite with poor stability transformed into hard martensite during the punching processing of holes. In contrast, the retained austenite with a relatively high stability showed a positive effect during the whole hole expansion deformation process. It decreased the stress concentration and, thereby, improved the HER. Thus, the present study has found that it is of the greatest importance to improve the stability of the retained austenite in high-strength medium-Mn steel, and to suppress its transformation to martensite during the punching of holes in the steel.

(Invited) Controlled Synthesis of Cocatalyst-Semiconductor Hybrid Nanomaterials for Photocatalytic Water Splitting

With the escalating global demand for energy, mitigating anthropogenic climate change necessitates the pursuit of carbon-neutral energy sources to diminish reliance on fossil fuels. Utilizing particulate photocatalysts for solar-light-driven water splitting presents a promising and sustainable paradigm for the large-scale production of storable and clean H2 fuel. To improve the solar energy conversion efficiency, coupling the photocatalysts with cocatalysts is a broadly adopted approach not only to facilitate charge separation and transport but also to serve as reaction sites and accelerate water-splitting reactions. Recent breakthroughs in colloidal synthesis enable the fabrication of advanced nanoparticles with precise control over size and composition. Colloidal NPs represent ideal cocatalyst candidates due to their capacity to provide numerous active sites and facilitate uninterrupted light absorption by the semiconductor. Here, we introduce our approach to synthesize cocatalyst-semiconductor hybrids as efficient photocatalysts, including the alloying of platinum group metal nanoparticle cocatalysts and the control of single-atom cocatalyst locations on semiconductor nanoparticles.Platinum group metals exhibit high efficiency as cocatalysts in the hydrogen evolution reaction, attributed to their favorable catalytic and electronic properties. Bimetallic alloy systems, in general, can considerably modulate their electronic structures, resulting in exceptional physicochemical properties surpassing those of their monometallic counterparts. Herein, we synthesized PtRu solid-solution alloy nanoparticles as high-performance H2 evolution reaction cocatalysts. The rational integration of PtRu nanoparticles with Al-doped SrTiO3 photocatalyst through liquid-phase adsorption and successive two-step annealing ensure the uniform deposition of PtRu alloy nanoparticles with a solid-solution structure. The bimetallic synergy between Pt and Ru induces higher electrocatalytic activity for the hydrogen evolution reaction and a superior electron-capturing property than its Pt counterpart. Modification of Al-doped SrTiO3 with PtRu alloy nanoparticles, CrOx, and CoOOH results in efficient photocatalytic overall water-splitting activity with an apparent quantum yield of 65% at 365 nm. This work introduces a framework to elucidate catalytic trends, offering rational design guidance for the development of bimetallic solid-solution nanoparticles as highly active cocatalysts for overall water splitting.Single-atom cocatalysts dispersed on semiconductor materials exhibit outstanding heterogeneous catalytic properties through the interactions between the single atoms and the photocatalyst. The nature of these interactions depends on whether the single atoms are located on the surface or within the interior of the photocatalyst. In this work, the location-selective placement of single atoms is achieved by carefully adjusting experimental procedure. Using CdSe nanoplatelets as a support, applying different Pt precursor complexes, solvent, and workup process resulted in location selective deposition of Pt atoms outside/inside CdSe nanoplatelet support. In photocatalytic hydrogen evolution reaction, the surface-adsorbed single Pt atoms exhibit higher stability than the substituted ones. This study provides a viable strategy for the structurally precise synthesis and design of single-atom catalysts.

Preparation of high-strength and high-ductility medium Mn steel with chemistry heterogeneous via a two-step intercritical annealing process

Recently, the retained austenite (RA) with chemically heterogeneous has attracted great attention in medium Mn steel. In this work, we designed a two-step intercritical annealing (TIA) heat treatment process to prepare high-strength medium Mn steel with the chemical composition of Fe–0.20C–8.0Mn–1.6Si–1.3Al (wt.%). Compared with the normal intercritical annealing (IA) heat treatment process, the TIA process can not only increase the volume fraction of RA but also obtain the RA with inhomogeneous Mn distribution. Meanwhile, it was found that the Mn content on the outer side of this structured RA was higher than that on the inner side, forming a nanoscale Mn-enriched layer on the outer side of RA, which played a significant role in improving the stability of RA. Finally, we used the TIA process to obtain medium Mn steel with an ultimate tensile strength (UTS) of 1611.83 MPa, a total elongation (TE) of 45.02%, and a product of strength and elongation (PSE) of 72.56 GPa·%, which achieves a superior combination of high strength and high ductility in medium Mn steel.

Room temperature-produced chalcogenide superlattices for interfacial phase-change memory

Phase-change memory (PCM) using chalcogenide films composed of Ge–Sb–Te alloys is the only commercially available nonvolatile memory for storage class memory. Recently, superlattice films of GeTe and Sb2Te3, called interfacial PCM (iPCM), have attracted attention for further increasing the switching speed and reducing energy consumption. It has been reported that the iPCM device exhibits both unipolar- and bipolar-type resistive switching depending on the method of voltage application, and research is being conducted to advance its applications. However, all iPCMs reported thus far have been formed at high temperatures beyond the crystallization temperatures of GeTe and Sb2Te3 using vacuum chambers equipped with a heating stage, making mass production and practical application difficult. Here, we report on fabricated superlattice composed of S-doped GeTe and Sb2Te3 layers by combining room temperature deposition with subsequent two-step annealing. Upon evaluating the performance of this superlattice film as a bipolar-type iPCM, it was found to exhibit characteristics comparable to those of bipolar-type iPCM fabricated from high-temperature deposited superlattices. This technology is expected to contribute to an increase in the throughput of iPCM device manufacturing.

Molecular dynamics simulation and experimental study of the material machinability characteristics and crack propagation mechanisms for fused silica double nanoscratches

Fused silica is a high-purity, hard and brittle, difficult-to-machine amorphous material that is widely used in the aerospace, optical instruments, semiconductors, microelectronics and other important fields. However, the influence of adjacent scratches on material deformation and subsurface damage during ultraprecision machining by abrasive particles is not well understood. This study aims to investigate the influence of micron-spaced double scratches on the deformation and damage for fused silica through molecular dynamics simulations and double nanoscratch experiments. An amorphous model of fused silica is created using a two-step simulated annealing method with three-directional periodic boundary conditions. Variable loaded double scratches with different nanometer distances are simulated on the surface of the model, and variable loaded double scratch experiments with varying micron-sized distances between scratches are conducted for fused silica wafers. The simulation and experimental results reveal that the deformation of fused silica during nanoscale double scratching involves both elastic and plastic deformation, and the surface and subsurface damage primarily consists of radial, lateral, Hertzian, and median cracks. The distance between the double scratches affects the load variation, surface and subsurface crack propagation, extent of material damage and removal rate, and surface roughness. Examination of the material subsurfaces using the FIB-TEM sample preparation and testing technique shows that the distance between the double scratches also influences the subsurface damage to the material.

Two-step annealing synthesis of MOF-derived Cr-Co-Ru metallic oxides for improving the oxygen evolution reaction in acidic water splitting

The development of acid-sensitive OER (Oxygen Evolution Reaction) electrocatalysts based on ruthenium oxides is a crucial step toward achieving large-scale hydrogen production in low-cost Proton Exchange Membrane (PEM) electrolyzers. However, a major challenge in this field is to overcome the tendency of ruthenium-based metal oxide dissolving in acidic environments, which affects long-term stability. In this study, we employed MIL-88B(Cr) as a precursor and used a two-step annealing method to prepare trimetallic metal oxides Cr0.5CoxRu0.5-xO2-δ. Detailed experimental measurements demonstrate that the introduction of Co reduced the volume of individual catalyst crystallites without disrupting the rutile crystal structure and inherent activity of CrO2@RuO2. Simultaneously, Co and Cr doping lowered the oxidation state of Ru within the catalyst system. Lower oxidation states of Ru are more stable during the OER reaction, ensuring the stability of this catalyst to be at least 100 hours. Furthermore, Co incorporation raises the energy required for oxygen vacancy formation, reduced the involvement of lattice oxygen, and enhanced the catalyst's activity. The catalyst Cr0.5Co0.17Ru0.33O2-δ with the best performance exhibited the overpotential of only 224 mV at 10 mA cm-2 in 0.5 M H2SO4. This study offers a viable strategy for developing highly active and stable catalysts in acidic media by controlling the electronic structure of RuO2.

Multiple-functional LiTi2(PO4)3 modification improving long-term performances of Li-rich Mn-based cathode material for advanced lithium-ion batteries

Li-rich layered oxides with high energy densities have become one kind of promising cathode for advanced lithium-ion batteries, however some issues are severely hindering their practical applications. To address these challenges, fast ion conductive LiTi2(PO4)3 (LTPO) is employed to modify the typical Li-rich cathode Li1·2Mn0·56Ni0·17Co0·07O2 (LMNCO) via a sol-gel process combined with a two-step annealing treatment in this work. Serving as a physical separator, LTPO coating effectively depresses the side reactions at cathode-electrolyte interface and the transition-metal dissolution from LMNCO active material under harsh electrochemical environment. Meanwhile, LTPO layer with high ion conductivity could facilitate the interfacial Li+ diffusion during charge/discharge process. In addition, partial Ti4+ ions doped into LMNCO effectively elevate the oxygen electronegativity and restrain the excessive oxidization of lattice oxygen, thus stabilizing the crystal structure and alleviating the stress-strain propagation upon cycling. Electrochemical characterization results demonstrate that the LTPO-modified LMNCO cathode exhibits a superior capacity retention of 86.5 % after 400 cycles at room temperature and that of 73.7 % even under an elevated temperature of 45 °C after 250 cycles under 1C. This study provides a facile strategy for the surface modification of Li-rich layered-structure oxides, which also sheds light in enhancing electrochemical performances for various cathode materials.

Ultrasensitive and selective hydrogen sensing of SnO2 nanofibers decorated with Pd single atoms

Highly accurate and sensitive hydrogen detection particularly at (sub)ppb level is crucial for large-scale use of green hydrogen energy. However, state-of-the-art hydrogen sensors usually have a ppm-level limit of detection (LOD). In this work, SnO2 nanofibers were decorated with Pd single atoms using a scalable two-step annealing method, which remarkably boosted the H2 sensing properties. The Pd-SnO2 nanofiber sensor exhibited a response of 224 to 1000 ppm H2 at the optimum operation temperature of 300°C, which was 107 times higher than that of SnO2, achieving an LOD as low as 0.6 ppb. Moreover, a fast response time of 8.4 s, excellent selectivity, and humidity tolerance were observed. The superior H2 sensing performance of Pd-SnO2 nanofiber was ascribed to excellent catalysis of Pd single atoms and formation of heterojunction.

Durable Ru Nanocrystal with HfO2 Modification for Acidic Overall Water Splitting

HighlightsHeterostructure constructed via confining crystalline ruthenium nanodomains by hafnium dioxide matrix was fabricated through a two-step annealing method for overall water splitting.The synergistic effect of hafnium dioxide modification and small crystalline domain formation significantly alleviates the over-oxidation of ruthenium.

Effect of polyvinylpyrrolidone concentration on optical properties of CuCrO2 thin films

In this study, CuCrO2 thin films were fabricated by spin-coating technique on alkali-free glass substrates and a two-step annealing process. The copper-based delafossite CuCrO2 is a p-type transparent conductive oxide that exhibits a wide energy bandgap and excellent stability. To improve the transmittance of CuCrO2 thin films, polyvinylpyrrolidone (PVP) was used as a porogen for preparing thin films with high transmittance and high haze values. The highest transmittance of 73.75% was achieved with 0.5 g of PVP. The bandgaps of prepared CuCrO2 thin films were estimated at 2.82 eV to 3.11 eV. The prepared CuCrO2 thin films had a porous structure and high transmittance. The high potential transmittance of porous CuCrO2 thin films makes them applicable to photovoltaic systems, transistors and touch screens or displays in the future.

Reutilization of Silicon-Cutting Waste via Constructing Multilayer Si@SiO2@C Composites as Anode Materials for Li-Ion Batteries.

The rapid development of the photovoltaic industry has also brought some economic losses and environmental problems due to the waste generated during silicon ingot cutting. This study introduces an effective and facile method to reutilize silicon-cutting waste by constructing a multilayer Si@SiO2@C composite for Li-ion batteries via two-step annealing. The double-layer structure of the resultant composite alleviates the severe volume changes of silicon effectively, and the surrounding slightly graphitic carbon, known for its high conductivity and mechanical strength, tightly envelops the silicon nanoflakes, facilitates ion and electron transport and maintains electrode structural integrity throughout repeated charge/discharge cycles. With an optimization of the carbon content, the initial coulombic efficiency (ICE) was improved from 53% to 84%. The refined Si@SiO2@C anode exhibits outstanding cycling stability (711.4 mAh g-1 after 500 cycles) and rate performance (973.5 mAh g-1 at 2 C). This research presents a direct and cost-efficient strategy for transforming photovoltaic silicon-cutting waste into high-energy-density lithium-ion battery (LIB) anode materials.

An enhanced strain response in micrometer-thick BNT-ST thin films

Lead-free Bi0.5Na0.5TiO3-SrTiO3 (BNT-ST) thin films with various thicknesses were deposited on the Pt(111)/Ti/SiO2/Si(100) substrates employing a sol-gel technique with a two-step annealing process. Despite the variations in thickness, the films exhibited a consistent polycrystalline structure, evidenced by identical diffraction peaks, albeit with differences in intensity. An imprint became evident in micro-thick films, increasing with film thickness. Also, the emergence of self-polarization was observed in thicker films detected by piezoresponse force microscopy. Noteworthy is the pronounced influence of film thickness on strain response, with the 1.38 μm-thick films demonstrating a large strain of 1.18%. The outstanding strain response can be attributed to the notable contribution of electric field-induced phase transition and polarization dynamics. This work provides a promising potential application of micrometer-thick BNT-ST thin films in advanced actuator devices.

Dually-refined grain and precipitate microstructure of ATF-FeCrAl alloy by a two-step annealing process to separate the recrystallization from precipitation

The service of ATF-FeCrAl cladding requires excellent mechanical properties, creep resistance and radiation resistance, which can be improved by microstructure refinement. Traditional thermomechanical process is difficult to refine the matrix and precipitates simultaneously due to the interaction between the precipitation and recrystallization. Here by separating the recrystallization from the precipitation process, we proposed a two-step annealing strategy to obtain both refined grain and precipitate microstructure. A warm-rolled FeCrAl alloy was firstly annealed at a high temperature for a short time to obtain an extended recovery or recrystallized microstructure without significant precipitation. Then low-temperature annealing was applied to obtain homogenous and dense nano-sized precipitates without changing the grain size. Compared to the conventional one-step annealing processes, the alloy processed by the two-step process exhibited excellent radiation-induced hardening resistance, ultrahigh tensile strength (1064.9 MPa) at room temperature with an appreciable elongation (11.7%) and best resistance to degradation in tensile properties during exposure at 800 °C. The “dually-refined” microstructure obtained by the two-step annealing exhibits good stability under ion irradiation at 320 °C. The two-step annealing strategy can provide a promising pathway to achieve microstructure refinement for other alloy systems.