Mechanical Creep Research Articles

Development of Mg-3Al-0.5Zn-0.4Mn-1Gd Alloys as a Clavicle Bone Implant Material: A Literature Review

Abstract Magnesium alloys are widely used as implant materials such as Magnesium-Aluminium, Magnesium-Mangan, Magnesium-Zirconium, and others. These alloys still need further research regarding the mechanical properties of the alloy materials, resistance to corrosion rate, and anti-toxic properties to the human body. This article reviews the Magnesium alloy AZ31 (Magnesium-3Al-1Zn-0.4Mn) with the addition of the Gadolinium element as a candidate for the implant of the clavicle bone. The novelty of the proposed research is the change in composition in the form of a reduction of 0.5% Zn and the addition of 1% Gd. Furthermore, anodizing and coating treatment is implemented to improve the mechanical stability of the alloy. This alloy is supposed to improve the physical, mechanical, and chemical properties of magnesium. The addition of gadolinium can increase the mechanical strength, creep resistance, and rate of corrosion resistance.

Understanding the deformation creep and role of intermetallic compound-microstructure in Sn-Ag-Cu solders

Tin-based alloys are commonly used in lead-free solder joints in electronic interconnection applications, where creep can limit joint reliability. In this work, directionally solidified bulk solder alloys of different compositions (pure tin, SAC105 and SAC305) are mechanically tested under a constant load for each composition at room temperature to understand mechanical creep performance and quantify the role of different content of Ag3Sn and Cu6Sn5 intermetallic compounds (IMCs) in terms of secondary creep strain rate, microstructural evolution, and total amount of accumulated strain. In this work, microstructures are fabricated using directional solidification to promote a systematic variation in IMC sizes, shapes, and distributions within similar crystal orientations of the primary β-Sn matrix. Analysis of creep data indicates that secondary creep is dominated by obstacle-controlled dislocation motion. This is further confirmed by electron backscatter diffraction (EBSD) analysis, which reveals that the formation of subgrains and internal structure, correlating to the initial microstructure of the sample, i.e. changes in secondary dendrite arm spacing (λ2) and eutectic intermetallic spacing (λe). The experimental observations are supported further by crystal plasticity simulations that explicitly model the presence of IMCs within the Sn-based samples and show the dependence of the secondary creep rate upon the IMC content, and therefore be beneficial for the possible future composition design in solders.

Experimental study on the mechanical properties of red sandstone with fractures under different loading rates

In order to study the effects of crack inclination angle and loading rate on rock mechanical properties, creep characteristics, and failure characteristics. Taking homogeneous red sandstone with different fracture angles as the research object, uniaxial compression tests and uniaxial compression creep tests were conducted at different loading rates. The results showed that under the same fracture angle, the loading rate was positively correlated with the peak strength, elastic modulus, instantaneous strain, creep strain, and steady-state creep rate of the sample, while negatively correlated with the peak strain. At the same loading rate, the mechanical properties and creep properties of the sample were controlled by the crack inclination angle α. With the increase of α, the peak strength, peak strain, instantaneous strain, creep strain and steady-state creep rate decreased first and then increased, and the elastic modulus increased. On the basis of rock creep testing, it is also important to establish a creep model that conforms to the actual test situation for studying rock creep characteristics. However, many models currently used cannot accurately describe the three stages of rock creep, especially the accelerated creep stage. Therefore, based on Burgers elements, this paper introduces plastic damage bodies based on damage rates and software components based on fractional calculus, A new creep model was obtained and its rationality was verified through experimental results. The results showed that the fit between the model and experimental data was above 0.97, indicating that the model can better describe the three stages of rock creep, especially reflecting the non-linear characteristics of the accelerated creep stage.

Influence of Si on the Elevated-Temperature Mechanical and Creep Properties of Al–Cu 224 Cast Alloys during Thermal Exposure

The influence of Si content (0.1–0.8 wt.%) on the development of precipitation microstructures and the resultant mechanical and creep properties during thermal exposure, up to 1000 h at 300 °C, in Al–Cu 224 cast alloys, was systematically investigated. The room and elevated temperature yield strength (YS) increased with increasing Si content under the T7 condition, which was attributed to the fact that the Si promoted the precipitation of fine θ′. However, Si increased the coarsening of θ′ during thermal exposure at 300 °C, and the alloys with low Si exhibited a higher YS and creep resistance at elevated temperatures than high Si alloys. The mechanical strength and creep resistance were mainly controlled by the precipitation strengthening of the predominant θ′ phase. Because of the high mechanical strength and creep resistance of the 0.1Si alloy during long-term thermal exposure, the Si level in Al–Cu alloys should be maintained at a low level of 0.1 wt.% for high-temperature applications. The strengthening mechanisms were quantitatively analyzed, based on the characteristics of the precipitate. The predicted YS values under different exposure conditions agreed well with the experimentally measured values.

Mechanical Properties of P91 Steel (X10CrMoVNb9-1) during Simulated Operation in a Hydrogen-Containing Environment.

P91 steel (X10CrMoVNb9-1) is widely used in the energy industry. It is characterized by good mechanical properties, creep resistance, corrosion resistance, impact toughness, and resistance to thermal fatigue. Due to their operating conditions and martensitic structure, components made from P91 steel are often subject to damage related to the presence of hydrogen. This article compares the results of the mechanical properties evaluation for P91 steel in an aggressive solution charged under load and without load. Based on the research, it was found that the hydrogen environment significantly affects the mechanical properties of P91 steel, reducing strength and yield strength, and decreasing ductility. It was revealed that in samples tested after 72 h without preloading, the tensile strength decreased by 1.5%, and the elongation decreased by about 29% for the sample, compared to the delivered condition sample. Under loaded conditions, the difference in tensile strength increased by approximately 8%, while elongation increased by nearly 50.

Integrating dynamic relaxation with inelastic deformation in metallic glasses: Theoretical insights and experimental validation

Metallic glasses (MGs), a metastable material far from equilibrium, exhibit intricate dynamic relaxation behaviors. The challenge lies in developing a model that accurately describes the dynamics and deformation mechanisms of MG. This paper introduces a model integrating dynamic relaxation with deformation behavior. Validation through dynamic mechanical analysis, stress relaxation, creep, and strain recovery tests confirm the existence of four deformation modes: elasticity, anelasticity from β relaxation, anelasticity from α relaxation at low temperatures, and viscoplasticity from α relaxation at high temperatures. The model captures all of these deformation modes. The dynamical mechanical spectrum and stress relaxation spectrum unveil dynamic features during glass to liquid transition, and a simple and effective experimental method was developed for identifying ultra-low-frequency dynamic relaxation. This work provides new perspectives on the study of relaxation dynamics in glassy states and establishes important connections between dynamic relaxation behavior and deformation mechanisms. These findings lay a theoretical and experimental foundation for the broad application of MGs.

Improvement of mechanical properties of TATB-based polymer bonded explosive by surface confinement and interfacial strengthening

Improvement of mechanical properties of 1, 3, 5-triamino-2, 4, 6-trintrobenzene (TATB) based polymer bonded explosives (PBX) is extremely desirable but still a big challenge. In this study, surface confinement and interfacial strengthening strategies were used to enhance the mechanical properties of TATB-based PBX. Firstly, TATB crystals were coated with a polydopamine (PDA) layer. Subsequently, various amounts (0.3, 0.5 and 0.8 wt%) of neutral polymeric bonding agent (NPBA) were grafted onto the PDA layer using 2,4-toluene diisocyanate as a molecular bridge. The results showed that the modified TATB composites-based PBX exhibited improved mechanical strength, as well as creep resistance properties compared to the raw TATB-based PBX. The modified TATB composites-based PBX with 0.5 wt% NPBA grafting content exhibited the highest mechanical strength and creep resistance due to the surface confinement effect of the rigid crosslinked PDA layer and interfacial strengthening effect of the NPBA layer. Present work might provide a promising strategy for synergistically improving the mechanical properties of TATB-based PBX.

Temporal evolution of fracture transport properties of fractured shales during long-term stress compaction

Understanding the temporal evolution of fracture transport properties in shales is of increasing importance for the long-term safe operation of many underground engineering projects. Here, a series of long-term (60 days each) water seepage and gas breakthrough experiments utilizing three shale samples, each with a single artificial fracture, was conducted to evaluate the time-dependent evolution of permeability and gas breakthrough pressure (GBP) under constant confining stress. Our results show continuous decreases in permeability and increases in GBP with time, and the rate of change in both is initially rapid but then slows. As the loading time increases, the permeabilities and GBPs become relatively constant. The inferred mechanisms are aperture reductions caused by mechanical creep and clay swelling of fractures. Pretest and posttest scans of fracture surfaces reveal some changes in asperity height, which demonstrates the occurrence of mechanical damage to the fracture during the experiments. Long-term stress compaction causes flow channels to narrow or even partially close over time. The fluid flow in confined fracture is controlled by some narrow apertures in the flow channels, which act as bottleneck points. The apertures at these points decrease to the micro-nano level under stress, significantly reducing fracture transport properties. While the fracture transport properties of fractured shale obviously decrease during long-term stress compaction, residual fracture voids still dominate the fluid flow over a longer period, and are especially prone to gas escape.

Kenaf/glass fiber‐reinforced polymer composites: Pioneering sustainable materials with enhanced mechanical and tribological properties

AbstractHybrid kenaf/glass fiber reinforced polymer composites have emerged as promising structural materials, garnering significant attention due to their unique blend of natural kenaf fibers and synthetic glass fibers. However, despite their potential, there remains a gap in the comprehensive understanding of their quasi‐static mechanical behavior, creep resistance, and fatigue performance. This paper addresses this gap by presenting recent advancements in studying these key properties of hybrid composites. Studies reveal that the combination of kenaf and glass fibers results in enhanced tensile, flexural, and impact strengths compared to individual fiber composites. Additionally, the hybridization offers improved creep resistance, with the glass fibers reinforcing the polymer matrix against deformation under sustained loads. Furthermore, investigations into fatigue properties demonstrate the resilience of hybrid composites to cyclic loading, contributing to prolonged service life in high‐stress environments. By elucidating the interplay between kenaf and glass fibers, this review underscores the potential of hybrid composites in various structural applications. The synergistic effects between natural and synthetic fibers offer a balance between sustainability, performance, and durability, making hybrid kenaf/glass fiber reinforced polymer composites a compelling choice for industries seeking lightweight, high‐performance materials in which aligns with the sustainable development goals (SDGs) especially on Goal 12.Highlights In composite engineering, combining glass and kenaf fibers could cut production costs, yield high‐performance materials, and promote green technology. Substituting part of the glass fiber with kenaf can enhance the strength‐to‐weight ratio and promote greater biodegradability in current synthetic composites. Quasi‐mechanical properties of hybrid kenaf/glass‐based composites was enhanced by optimal stacking sequences, filler addition, and fiber treatment. Failures due to fatigue and creep can be reduced by hybridizing kenaf/glass fiber composites can prevent in polymer composite due to enhance elastic modulus. Enhanced tribological performance of hybrid kenaf/glass‐based composites due to less damage in microstructure via good interlocking of kenaf and glass in matrix.

Biomimetic design of polyisoprene rubber with terminal synergistic effects leading to mechanical properties and creep resistance boost

The enhancement of polyisoprene rubber performance through biomimetic simulation of the terminal effect of natural rubber has been explored. So far, the presence of synergistic effects between different terminal groups and the challenge of controlling the relaxation behavior of non-covalent bonds while preserving their advantages remain open questions. In this study, we successfully prepared natural rubber biomimetic polymers with different functionalized terminals. Specifically, we constructed terminal-olefin cross-linking points at one end of the polymer chains, while dissociable oligopeptide assemblies were formed at the other end. Investigation of the viscoelastic behavior of the polymers and the structure of the rubber network confirmed the existence of synergistic effects between different terminal groups. The terminal-olefin cross-linking points effectively anchored the rubber network and stabilized the non-covalent bonds. Simultaneously, the non-covalent bonds formed by the oligopeptides acted as weak bonds, dissipating energy and improving the dimensional stability and mechanical properties of the vulcanized rubber.

Optimization of measurement and calculation methods for viscoelastic creep strain and mechanical adsorption creep strain during conventional drying process of Pinus sylvestris

The traditional measurement method for viscoelastic creep strain and mechanical adsorption creep strain has relatively low accuracy, making it difficult to ensure the data accuracy of specimen strain measurements. In this study, 50-mm-thick Pinus sylvestris sawn timber was used as the research object. Along the thickness direction of the test material, the relationship between the free shrinkage coefficient and the moisture content of the test material was studied to optimize the measurement methods of viscoelastic creep strain and mechanical adsorption creep strain during drying process. The results showed that the optimized measurement method for viscoelastic creep strain, which compensates for dimensional change caused by moisture content changes during the creep recovery phase, was applied to different layers in the thickness direction of the test material. The average relative error at the end of the drying stage was reduced 20.1% compared to the traditional method. For the mechanical adsorption creep strain in different layers of the test material’s thickness, the optimized measurement method, based on the free shrinkage size calculated from the free shrinkage coefficient and moisture content, reduced the average relative error 59.1% compared to the traditional method.

Microstructure, mechanical and electrochemical behavior of magnetron-sputtered carbothermic reduced iron-boride ceramic coatings

In this study, magnetron sputtered carbothermic reduced iron boride (FeB) coatings were developed on grey cast iron (GCI) substrates at different substrate temperatures. The impact of substrate temperature on structural, mechanical, and corrosion behavior was examined for two FeB deposition scenarios: FeB coatings deposited at room temperature (RT) and at 500 °C substrate temperature. The evolution of phases and microstructure was studied using XRD and FESEM, respectively. The mechanical properties, creep, deformation behavior, and adhesion strength (scratch test) of the deposited coatings were investigated using nanoindentation at ambient temperature. The highest hardness and Young’s modulus of 16 GPa and 231 GPa respectively, were achieved at 500 °C due to microstructural enhancement. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion behavior of the coatings. The results show that substrate temperature strongly influences the surface morphology of the coatings, which in turn governs the mechanical and corrosion behavior of the FeB coating. The FeB-coated GCI at 500 °C substrate temperature showed higher resistance to scratching, better mechanical properties, and improved corrosion resistance which is attributed to the enhanced adhesive strength, refined microstructure, and formation of protective oxide layers of FeB on the surface of the coatings.

Experimental study on mechanical damage and creep characteristics of Gonghe granite under real-time high temperature

It is significant to study the mechanical properties of hot dry rock (HDR) for the development of deep geothermal energy. At present, the creep behavior of granite under real-time high temperature is not fully understood. The creep behavior of granite at 25 ∼ 800°C was investigated by real-time high-temperature uniaxial compression and graded load creep tests, and the thermal damage mechanism of granite was studied by scanning electron microscopy (SEM) experiments. The paper systematically analyzes the evolution of mechanical indexes such as uniaxial compressive strength (UCS), elastic modulus, creep deformation, steady creep rate and long-term strength of granite under thermal-force coupling. The results show that the UCS and elastic modulus of granite increase with increasing temperature in the range of 25 ∼ 200 °C, and decrease with increasing temperature in the range of 200 ∼ 800 °C. The damage speed of granite is the fastest in the temperature range of 400 ∼ 600 °C. The steady creep rate of granite increases with the increase of temperature and stress level. The ratio of long-term strength to UCS decreases with increasing temperature, from 93.6% at 25 °C to 73.2% at 800 °C. The research results provide relevant thermal damage mechanical parameters and theoretical basis for the development of HDR.

Influence of Oxide Inclusions on the Creep Properties of Electron Beam Welds in Ti-added Reduced Activation Ferritic/Martensitic Steel

In this study, the effects of reducing oxide inclusions on the microstructure, tensile properties at 550 ℃, and creep resistance of electron beam welded (EBW) joints in Ti-added reduced activation ferritic/martensitic (RAFM) steel were investigated. Two RAFM steels, designated as Steel A and Steel B, were prepared by adjusting the Al and Si contents to contain different fractions of oxide inclusions. The microstructures of the base metal and heat-affected zone (HAZ) were analyzed, and the mechanical properties of the welds were evaluated. Reducing the Al and Si content in Steel B resulted in a decrease in both the fraction and size of oxide inclusions compared to Steel A. Both steels exhibited tempered martensitic microstructures with M23C6 and MX precipitates. Hardness tests revealed that the over-tempered HAZ (OTHAZ) was the weakest region. However, both tensile test and creep tests at 550 ℃ showed fractures occurring in the base metal, indicating that the low heat input of EBW effectively minimized the weak HAZ regions. Steel B demonstrated improved tensile properties and creep resistance due to the reduced oxide inclusions. It was found that Steel B had a significantly longer creep life than Steel A at 550 ℃. SEM analysis revealed ductile fracture characterized by dimples, where oxide inclusions containing Al, Si, Ta, and Ti were predominant. The presence of these inclusions reduced the effectiveness of solid solution and precipitation strengthening by consuming Ta and Ti. Additionally, microvoids could easily nucleate at the interface between the hard oxide inclusions and the soft metal matrix during creep. Therefore, the reduction of oxide inclusions improved deformation resistance and high-temperature stability, resulting in better creep resistance in Steel B. In conclusion, the reduction of oxide inclusions in Ti-added RAFM steel enhances the high-temperature mechanical properties and creep resistance of EBW joints, underscoring the importance of oxide control in the development of RAFM steels for fusion reactor applications.

Perbandingan Keutuhan Permukaan Bahan Inkonel 718 dalam Pemesinan Kriogenik dan Kering

Inconel 718 is a nickel-based alloy that has been developed with superior mechanical strength, creep resistance, and corrosion, as well as erosion resistance at temperatures above 649 ˚C. It is suitable to be used for aircraft engine components such as turbine discs. However, it also has low heat conductivity and the presence of hard carbide particles in its alloy worsens the machining conditions with high cutting temperature, and high shear force and promotes work hardening. Thus, this study aims to evaluate the surface integrity of Inconel 718 in terms of surface roughness, plastic deformation, and micro-hardness alterations after the turning process. Cryogenic CO2 cooling was supplied along the cutting process to reduce cutting temperatures and the machining performances were compared with dry machining. The experimental works show that the dry machining resulted in lower surface roughness by up to 42.15% as compared to cryogenic. However, the depth of plastic deformation under dry machining was much more severe than in cryogenic machining driven by higher cutting temperatures and pressure from the worn tool. The depth of plastic deformation became more distinct as the cutting speed increased. While the microhardness alteration of the machined surface was higher under cryogenic machining due to extensive cooling capacity by the CO2 flow. Thus, this study reveals that cryogenic cooling during metal cutting can produce products that have better wear resistance as well as higher surface hardness.

Simulation Study of Coal Seam Gas Extraction Characteristics Based on Coal Permeability Evolution Model under Thermal Effect.

The permeability evolution law of high temperature and high stress coal seam is determined by the influence of multiphase coexistence and multifield coupling. In an environment greatly affected by disturbance and high temperature, the coal permeability model under the coupling of thermal and mechanical creep is not only a vital framework from which to examine gas migration law in multiphase and multifield coal seams but also an important theoretical foundation for gas control in coal seams. The influence of high-temperature environment on creep deformation and permeability is analyzed by several creep seepage tests under different temperature conditions.A mathematical model for the evolution of coal permeability considering the influence of temperature is established through the theory of matrix-crack interaction based on gas adsorption and desorption and thermal expansion deformation. Based on the permeability model under the coupling of thermal and mechanical creep, the numerical model of gas migration, seepage field, diffusion field, stress field, and temperature field is constructed, and the law of gas migration in coal seam under multifield coupling is explored. The influence law of thermal effect on gas extraction characteristics is analyzed, in which the time-varying mechanism of temperature field, the relationship between creep deformation and temperature and pressure, the influence of creep deformation on permeability, the dynamic distribution of gas pressure, and the change of gas extraction quantity are described in detail. It is concluded that the influence of temperature on permeability is much greater than that of creep deformation and that a high initial coal seam temperature is beneficial to gas extraction. It provides theoretical basis and technical guidance for the study of multifield coupled gas migration and coal seam gas treatment.

Review on manufacturability and strengthening mechanisms of particulate reinforced Mg composites

The further development of lightweight and energy-saving engineering materials is a great challenge for scientists in the 21st century. Magnesium and its composites, as the metal materials with the lowest density among metal structural materials, have good thermal conductivity, good dimensional stability, high specific strength, good biocompatibility, which can meet the requirements of energy-saving, emission reduction, environmental protection. In recent years, magnesium and its composites have found the major applications in various fields such as aerospace, automotive industry, electronics and medical industry. However, the fabrication of magnesium matrix composites is difficult, and the deformation behaviors and strengthening mechanisms of particulate reinforced magnesium matrix composites have unique characteristics. This article reviews the recent research progress of the magnesium matrix composites, including different fabrication methods and strengthening mechanisms. According to the classification of solidification rate, the advantages and disadvantages of various techniques used to fabricate magnesium matrix composites were introduced. The traditional and novel fabrication techniques were discussed. The influence mechanisms of particulates on solidification microstructures, recrystallization behaviors, texture strength and twin behaviors of magnesium matrix composites during solidification and extrusion were summarized, and the roles of particulates in solidification and extrusion of magnesium matrix composites were analyzed. The strengthening mechanisms of particulates on the mechanical properties, corrosion resistance, fatigue resistance and creep resistance of magnesium matrix composites were revealed. Finally, the development prospect and research direction of magnesium matrix composites were prospected. It is hoped that this paper can provide a reference for the further development of magnesium matrix composites.

Unexpected effects on creep resistance of an extruded Mg-Bi alloy by Zn and Ca co-addition: Experimental studies and first-principles calculations

In the present work, a new Mg-Bi based alloy is developed by the addition of Zn and Ca in equivalent atom fraction with Bi. Mg-Bi and Mg-Bi-Zn-Ca alloys were prepared by extrusion at a ram speed of 20 mm/s. Room temperature mechanical properties and creep behaviors at 423 K were investigated. The results show that Zn and Ca co-addition shows little influence on average grain size and texture intensity but changes the dispersive Mg3Bi2 into Mg2Bi2Ca particles in different sizes and a lower density. Twinning is largely activated during room-temperature deformation. Consequently, a slightly decreased proof strength but tripled elongation is shown at room temperature. Unexpectedly, large enhancement in creep resistance is detected after the co-alloying of Zn and Ca and the minimum creep rate is reduced by 10 to 20 times in the BZX621 alloy. Stress exponent n = 4–5 indicates that the creep is a dislocation-climb controlled type. Post-mortem characterization on microstructure shows slip of dislocation 〈c + a〉 are also largely found in B6 as well as BZX621 alloy and cross-slip is detected more severe in B6 alloy. Dynamic segregation and precipitation are also seen in both alloys. Bi-clusters are seen dispersive across the grains in B6 and so did the PFZs that could undermine creep resistance at the grain boundaries. By contrast, Zn-rich needle-like precipitates are developed at most “ends” of 〈c + a〉 dislocations, which would hinder the further dislocation motions and thus improve the creep resistance. First-principles calculations were adopted and the results show that the thermal stability and thermomechanical properties of Mg2Bi2Ca are much better than that of Mg3Bi2. Stacking faults energy is lowered down with the co-addition of Ca and Zn, which could inhibit the rate of dislocation climb and cross-slip. As a result, the improved creep resistance is obtained in the Mg-Bi-Zn-Ca alloys. Microstructural and controlling mechanism changes by thermal activation result in the unexpected enhancement in creep resistance with decreased room-temperature proof strength after co-addition. These findings could contribute to the development and optimization of creep-resistant Mg alloys in the future.

Opportunity of ferrimagnetic (CZLF)/ferroelectric (BZT) composite materials in high frequency applications

The ferrimagnetic Zn0.35Co0.65 La0.02Fe1.98O4 (CZLF) ferrite with cubic spinel structure (space group Fd3m) was made into composite by mixing with ferroelectric Ba0.5Zr0.5TiO3 (BZT) perovskite with tetragonal structure (space group P4mm) at the mass ratio. Disk-shaped composite powder was finally heated at 1100 °C to study the structure, dielectric and ferroelectric properties. The structural characterization for synthesized samples were carried out using Fourier transform infrared and Transmission Electron Microscopy. Fourier transform infrared show the successful formation of composite samples which is also observed from x-ray diffraction pattern. In compared to their ferrite counterparts before the composite, dielectric response and ferroelectric characteristics of the composite samples are noticeably altered. Compared to the ferrite samples, the composite system exhibits a higher permittivity. In composite samples, the space charge polarization, which was primarily effective at low frequencies and high measurement temperatures, is much diminished. The mechanical properties and indentation creep of these bearing alloys were studied by Vickers indentation testing at room temperature. The remnant polarization of BZT/CZLF increases with decreasing BZT content, which may be suitable for permanent memory device applications. Graphical abstract

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.