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The liner is affixed to the inner side of the ball mill cylinder to protect the cylinder. Through isothermal compression experiments, Arrhenius constitutive models, peak strain models, critical strain models, dynamic recrystallization dynamic models, and grain size models suitable for the forging process of Mn–Cr–Ni–Mo steel used in ball mill liners were established. By utilizing Deform software, a 3D thermo‐force‐structure coupling model for the hot forging process of ball mill liners was constructed, and the volume fraction of dynamic recrystallization and average grain size during forging was predicted. The response surface model was employed to investigate how process parameters interacted with each other and affected microstructure uniformity in ball mill liners. After optimization, the optimal parameters were determined: initial forging temperature at 1200 °C, forging speed at 30 mm s−1, and friction coefficient at 0.3. Subsequently, a hot forging experiment on ball mill liners was conducted using these optimized parameters; samples were analyzed through backscattered electron diffraction device experiments and microscopic tissue observations. Results demonstrated that microstructural changes observed during actual forging processes aligned with numerical simulation results—thus verifying both the accuracy of the Mn–Cr–Ni–Mo steel material model and numerical simulation method. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of 22Cr‐25Ni austenitic heat‐resistant steel at the temperatures of 950–1150 °C and strain rates of 0.01–10 s−1 is studied by isothermal compression test. It is found that the dynamic recrystallization (DRX) degree of the steel increases with the increase of temperature. The DRX degree decreases with the increase of the strain rate from 0.01 to 1 s−1, whereas the DRX degree increases with the increase of the strain rate from 1 to 10 s−1. The hot deformation activation energy is as high as 624.25 kJ mol−1 due to the addition of a large number of alloying elements. The typical strain compensation Arrhenius constitutive model established can be used to roughly predict the hot flow behavior of the steel. Furthermore, a modified model considering the influence of strain rate and deformation heat on the deformation process is proposed and showed higher accuracy (statistical parameters r = 0.994 and average absolute relative error = 4.59%). The DRX zone of the steel is determined to be 1080–1150 °C/0.01–0.1 s−1 through processing map analysis, representing the appropriate hot working zone. The microstructure corresponding to the instability zone in the processing map exhibits deformation concentration bands or necklace structures. [ABSTRACT FROM AUTHOR]

The effects of different deformation temperatures on the dynamic recrystallization (DRX) behavior and twinning of Incoloy 800H alloy were investigated by hot compression tests. The microstructures at different deformation temperatures were analyzed using electron backscattered diffraction. Additionally, the evolution characteristics of dislocations and twinning were observed by transmission electron microscopy (TEM). The research has found that the DRX behavior becomes more pronounced with the increase in deformation temperatures. At lower temperatures, discontinuous DRX (DDRX) promotes DRX along with continuous DRX (CDRX). As the temperature increases, the CDRX mechanism gradually weakens, and the DDRX mechanism becomes dominant. Furthermore, it can be observed through TEM that as the deformation temperature increases, the initial twins are gradually disappear and new twins formed inside the DRX grains, which promotes the microstructure's refinement. [ABSTRACT FROM AUTHOR]

In this work, ultrafine-grained (UFG) plates of AA2024/AA5083 laminated composite with alternating layers of heat-treatable aluminum AA2024 and strain-hardening aluminum AA5083 were fabricated through accumulative roll bonding (ARB) technique and were subsequently joined using underwater friction stir welding (UFSW). Friction stir welding (FSW) is a solid-state welding method which is suitable for the joining of similar and dissimilar UFG alloys of AA2024 and AA5083, which are mainly used in aerospace and aviation industries. Welding variables, such as pin profile, rotational speed, welding speed, and tilt angle were optimized using the Taguchi optimization technique. Different zones of UFSWed joints including stir zone (SZ), thermo-mechanically affected zone (TMAZ), and heat affected zone (HAZ) were investigated through OM, TEM, and SEM. The results showed that the tapered cylindrical pin, 1000 rpm rotational speed, 110 mm.min−1 welding speed, and 2.5° tilt angle were the optimal welding variables in terms of tensile strength. The microstructural results showed the formation of nano-size, recrystallized equiaxed grains with a size of 500 nm (the same size as that in the UFG base metal) in the optimal sample. The hardness in the weldment of the optimal UFSW sample decreased slightly, so that the efficiency of 85% was presented and the minimum hardness location (MHL) disappeared. The ultimate tensile strength (UTS) of 425 MPa and 64% efficiency were observed in the optimal conditions. Due to the presence of very fine grains and large dislocations, and the uniform distribution of precipitates in the underwater state, high strength and elongation were obtained. [ABSTRACT FROM AUTHOR]

Graphene/copper composites are promising in electronic and energy fields due to their superior conductivity, but microstructure control during thermal mechanical processing (TMP) remains a crucial issue for the manufacturing of high-performance graphene/copper composites. In this study, the hot deformation behavior of graphene/copper composites was investigated by isothermal compression tests at deformation temperatures of 700~850 °C and strain rates of 0.01~10 s−1, and a constitutive equation based on the Arrhenius model and hot processing map was established. Results demonstrate that the deformation mechanism of the graphene/copper composites mainly involves dynamic recrystallization (DRX), and such DRX-mediated deformation behavior can be accurately described by the established Arrhenius model. In addition, it was found that the strain rate has a stronger impact on the DRX grain size than the deformation temperature. The optimum deformation temperature and strain rate were determined to be 800 °C and 1 s−1, respectively, with which a uniform microstructure with fine grains can be obtained. [ABSTRACT FROM AUTHOR]

Magnesium alloys show great promise in high-speed transport, aerospace, and military technology; however, their widespread adoption encounters challenges attributed to limitations such as poor plasticity and strength. This study examines the high-temperature deformation of semi-solid forged AZ91D magnesium alloy through a combination of experiments and simulations, with a focus on comprehending the influence of deformation conditions on dynamic recrystallization (DRX). The findings disclose that conspicuous signs of DRX manifest in the yield stress curve as strain increases. Additionally, decreasing the strain rate and temperature correlates with a reduction in both yield stress and peak strain, and the activation energy is 156.814 kJ/mol, while the critical strain and peak strain remain relatively consistent ( ε c = 0.66208 ε p ). Microstructural changes during high-temperature deformation and the onset of DRX are thoroughly examined through experimental methods. Moreover, a critical strain model for DRX and a predictive model for the volume fraction of DRX were formulated. These equations and models, validated through a combination of experiments and simulations, serve as invaluable tools for predicting the mechanical behavior and microstructural evolution, which also establishes a foundation for accurately predicting the deformation behavior of this alloy. By analyzing the hot deformation characteristics and dynamic compression mechanism of the newly developed semi-solid forging AZ91D magnesium alloy, a numerical simulation model can be effectively established. This model objectively reflects the changes and distributions of stress, strain, and rheological velocity, providing a scientific basis for selecting subsequent plastic deformation process parameters and designing mold structures. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of as-extruded Mg-8Sn-4Al alloys micro-alloyed with Ag and Sc elements were investigated by optical microscopy, x-ray diffraction, scanning electron microscope and electron backscattered diffraction. The as-cast Mg-8Sn-4Al, Mg-8Sn-4Al-0.8Sc and Mg-8Sn-4Al-1Ag-0.8Sc alloys were extruded at 320 °C with an extrusion ratio of 25 without further solid solution and aging treatment. The microstructure of all as-cast and as-extruded Mg-8Sn-4Al alloy is composed of α-Mg matrix and Mg2Sn phase. The extrusion treatment and Ag and Sc addition obviously refine the grains and Mg2Sn phase. A complete dynamic recrystallization and a slight basal texture were observed in the as-extruded alloys. In addition, the stable block-shaped Al3Sc phase was also observed in Mg-8Sn-4Al alloys with Sc addition after extrusion treatment. Interestingly, the Sc or Ag-Sc addition simultaneously improves the tensile strength and elongation of as-extruded Mg-8Sn-4Al alloy. The enhanced ultimate tensile strength and tensile elongation of as-extruded Mg-8Sn-4Al-1Ag-0.8Sc alloy reach 318.07 MPa and 14.41%, respectively, which are higher than these of as-extruded Mg-8Sn-4Al alloy. This is mainly attributed to the grain refinement, Mg2Sn phase refinement and solid solution elements (Al, Ag and Sc). The Ag and Sc addition to as-extruded Mg-8Sn-4Al alloy is positive to dynamic recrystallization and mechanical property, and corresponding mechanisms are discussed in detail. [ABSTRACT FROM AUTHOR]

This study investigated the role of interfacial deformability in bond integrity and strength, particularly in the production of robust joints between harder austenitic stainless steels (SS) during ultrasonic welding. The specimen without the interlayer experienced limited strength enhancement owing to internal cracking from continuous sliding at interfacial temperatures below 0.6 times the melting point (Tm), which is attributed to the limited deformability of the austenitic SS. In contrast, introducing Fe and Ni interlayers between the substrates resulted in a notable increase in the interfacial strength, surpassing 2500 N in the peak load within a reduced welding duration. The correlation between the interfacial strength and the peak temperature suggests that a substantial decrease in hardness below 0.4 Tm is sufficient for extensive bond formation. Moreover, dynamic recrystallization (DRX) led to grain refinement in the Fe interlayer owing to shorter weld durations, whereas grain growth was observed in the Ni interlayer due to higher peak temperatures. Both the Fe and Ni interlayers significantly improved the bonding integrity by accommodating plasticity through the above phenomena without severe damage to the substrates, leading to increase of interfacial strength by 24% (2050 N to 2500 N) and reduction of weld duration by 40% (1.5 s in Fe interlayer). In addition, the fracture position after the lap shear test shifted from the edge of the weld area to the SS substrate. [ABSTRACT FROM AUTHOR]

To investigate the influence of Zn-alloying on the microstructure and tensile mechanical properties of Mg–6Bi alloy after hot extrusion, a new ternary Mg–6Bi–3Zn alloy was prepared by extrusion at 300 °C. The microstructures, texture, dynamic precipitates and tensile mechanical behaviors of the extruded alloy were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), electron backscattered diffraction (EBSD) and a material testing machine at room temperature. After extrusion, the Mg–6Bi–3Zn alloy possesses a bimodal microstructure with elongated large unrecrystallized (unDRXed) grains and fine dynamic recrystallized (DRXed) grains. In addition, non-basal <20 2 _ 1>//ED, <44 8 _ 3>//ED and <11 2 _ 1>//ED textures are observed within DRXed grains due to the Zn addition, leading to texture weakening in the extruded Mg–6Bi–3Zn alloy. Zn addition facilitates the dynamic precipitation behavior, leading to a 12.2% area fraction of Mg3Bi2 precipitates with an average size of 39.2 nm. Furthermore, incorporation of Zn atoms in Mg3Bi2 phases and segregation of Zn at the grain boundary are found. The extruded Mg–6Bi–3Zn alloy exhibits a tensile strength of 336 ± 7.1 MPa and a yield strength of 290 ± 5.5 MPa, as well as an elongation of 11.5%. Therefore, Zn addition is beneficial to enhance strength and keep good ductility for the extruded Mg–6Bi–3Zn alloy. [ABSTRACT FROM AUTHOR]

Continuous dynamic recrystallization (CDRX) forms a new recrystallized microstructure through the progressive increase in low-angle boundary misorientations (LAGBs) during the hot forming of metallic materials with high stacking fault energy (SFE), such as aluminum alloys. The present work investigates the effect of deformation parameters on the evolution of the dynamic recrystallization microstructures of an AA1050 aluminum alloy during compression at elevated temperatures. The alloy microstructure is investigated at deformation temperatures and strain rates in the range of 300 °C to 500 °C and 0.001 to 0.8 s−1. A well-defined substructure and subsequent DRX grains provide indication that recrystallization can proceed with continued strain under high-temperature compression. At a strain rate of 0.1 s−1, the DRX fraction is observed to be 0.25 at a temperature of 300 °C. This fraction increases to 0.32 as the temperature rises to 400 °C. The recrystallization mechanism is identified by analyzing the flow stress, the evolution of the subgrain misorientation angle, and the distribution of recrystallized grains. The observations of discontinuous dynamic recrystallization (DDRX) and CDRX under various deformation parameters are discussed. Moreover, the main substructure evolution laws observed from the high-temperature compression of an AA1050 Al alloy are summarized. [ABSTRACT FROM AUTHOR]

Incremental sheet forming (ISF) uses a simple CNC milling machine to produce 3D geometries at very low cost and time using the CAD geometry of the parts. Due to the localised plastic deformation of the process, it can be used to make it easier to shape materials that are hard to shape, such as magnesium and titanium. Magnesium AZ31B alloy sheets of 1.5 mm thickness were formed at room temperature using the conventional Erichsen cupping and ISF process to quantify the maximum room temperature formability of the alloy. Using the conventional Erichsen cupping test, a maximum forming depth of 2.88 mm was obtained. ISF was performed using the helical toolpath strategy up to fracture for three different feed rates (F) (50, 1000, and 2500 mm/min), spindle speeds (S) (50, 500, and 3000 rpm), and pitch sizes (P) (0.1, 0.5, and 2.5 mm). A maximum forming depth of 8.86 mm was obtained for the process parameter condition—F50S3000P0.5 during the ISF process. It was observed that the formability of the alloy was reduced with increasing feed rate and pitch size, whereas it was enhanced while increasing the spindle speed. The starting material possessed a strong basal texture, which does not favour the activation of (10–12) tension twins during the uniaxial stretching of the conventional process. In contrary, the enormous frictional heat generated at high spindle speed (3000 RPM) and the plane strain and biaxial stretching nature of the ISF process resulted in the activation of newer twins during the ISF process, thereby improving the formability of the alloy sheets up to 8.86 mm. This shows that the ISF process is capable of forming hard-to-shape materials, like magnesium, at room temperature without compromising their excellent ambient temperature mechanical properties. It is also imperative that the ISF process can be used as a substitute to the conventional forming process and form Mg AZ31 sheets at room temperature at very low cost and lead time, thereby widening its usage in the automotive sectors. The higher formability of AZ31B sheets at room temperature imparted by the ISF process will be useful to down-gauge the input sheet metal thickness, thereby improving the fuel efficiency and reducing carbon emission in the automotive sector. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, a pure zinc sample was prepared by extrusion at room temperature and its microstructure evolution during tensile testing was studied by electron back-scattering diffraction (EBSD). The average grain size of the extruded zinc is 13.8 μm. Extruded pure zinc exhibited excellent ductility (60.4 ± 3.1%). The stress of the extruded pure zinc sample increased first and decreased when the strain was more than 20%, the ultimate tensile strength is 154 ± 1.4 MPa. EBSD results showed that dislocation slip was the main deformation mechanism when the strain was less than 15%, followed by dynamic recrystallization (DRX) and grain growth. The high strength and plasticity of pure zinc are due to grain refinement and DRX. These findings are expected to provide an important new pathway for designing and highly developing strength and plastic zinc products. [ABSTRACT FROM AUTHOR]

The evolution of microstructure has a significant impact on the coordinated deformation of bimetallic materials at high temperatures. This study conducted hot compression experiments on the 40Cr/Q345B bimetallic ring blanks. Based on EBSD measurement data, the parent austenite was reconstructed, and the dynamic recrystallization (DRX) fraction was evaluated using a grain orientation spread method. The DRX evolution of bimetallic ring blanks during hot deformation was studied, and the effects of different deformation conditions on the microstructure, microhardness, and interface element diffusion were analyzed. The coordinated deformation mechanism of the bimetallic ring blank at high temperatures was investigated. The results indicate that the 40Cr/Q345B bimetallic ring blank produced by centrifugal casting formed a 4.2 mm thick bonding layer (BL), with a smooth transition of elements, microstructure distribution, and grain size. The DRX evolution of 40Cr, BL, and Q345B was not synchronized, and the DRX of 40Cr occurred earlier with stable deformation. Q345B had a lower degree of DRX and a tendency of localized flow. The evolution of the BL approached 40Cr. When the strain reached 0.69, the DRX volume fractions of 40Cr, BL, and Q345B were 88.25%, 81.9%, and 53.77%, respectively. At higher temperatures and lower strain rates, the average grain sizes of 40Cr, BL, and Q345B were 150.6, 139.33, and 128.84 μm with severe grain coarsening. Coordinated deformation was enhanced by increasing the temperature and strain rate. Higher temperatures or lower strain rates increased the thickness of the metallurgical BL by promoting element diffusion. The synergistic strengthening effect of heterogeneous deformation induced strengthening and work hardening, combined with the DRX evolution gradient at the BL, played a coordinating role in the microstructure evolution of the bimetallic ring blank. [ABSTRACT FROM AUTHOR]

Copyright of Iron Steel Vanadium Titanium is the property of Iron Steel Vanadium Titanium Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The microstructure evolution, plastic deformation, and damage severity during the open die hot forging of a martensitic stainless steel were investigated using finite element (FE) simulation. A microstructure evolution model was developed and combined with a visco-elastoplastic model to predict the strain, the strain rate, and the temperature distribution, as well as the volume fraction and the size of dynamically recrystallized grains over the entire volume of an industrial size forging. The propensity to damage during hot forging was also evaluated using the Cockcroft & Latham model. The three models were implemented in the FE code and the results analyzed in terms of microstructure inhomogeneity and stress levels in different regions of the forging. A good agreement was obtained between the predicted and the experimental results, demonstrating that the simulation provided a realistic representation of the forging process at the industrial scale. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Plasma arc additive manufacturing (PAAM) stands out for its remarkable efficient utilization and good performance reliability, making it a highly favored additive manufacturing technique. This study delves into the tensile deformation below δ-solvus temperature of PAAM IN718 alloy with complete heat treatment. The results show that the peak stresses are decreased from 1069 to 1189 MPa at 550 °C to 620–1059 MPa at 750 °C. Through the orientation distribution function, the domain textures for hot deformation were identified as cube texture and Rt-Goss texture {110}. The results of the observations on the substructure and grain boundary components of the deformed alloy confirmed that the onset temperature of recrystallization in PAAM alloy is approximately 750 °C. The recrystallization nucleation mechanism of PAAM IN718 alloys was identified as discontinuous dynamic recrystallization. A deformation constitutive equation for hot deformation was established using the Zener-Hollomon parameter, with an average activation energy of 508.93 kJ/mol. A processing map for the hot working of PAAM alloy was developed, and the reasonable processing domains are located at a temperature 700–750 °C/strain rate 10−2–10−1 s−1 with a power dissipation efficiency range of 0.41–0.47. The high-temperature fracture mechanism of PAAM alloy was discussed, identifying the important inducements for high-temperature fracture failure including carbides, residual Laves phase, and δ phase in the PAAM alloy.

This study investigates the hot compression behavior of a molybdenum- Rhenium (Mo–Re) alloy, focusing on deformation mechanisms and instability. Utilizing electron backscattered diffraction (EBSD) and transmission electron microscope (TEM), we characterized the microstructure, grain orientation, and deformation behavior across temperatures (650, 750, 850, and 950 °C) and strain rates (0.01, 0.1, 1, and 10s-1). The study reveals that Mo–Re alloys exhibit high hot deformation resistance, necessitating optimal processing conditions for effective plastic deformation. Key findings by EBSD and TEM include the formation of dislocation networks and substructures enhancing grain plasticity. We established a constitutive equation and processing maps, providing valuable insights for industrial applications and future alloy development.

6061 aluminum alloys with different aging states were prepared by rotational friction extrusion （RFE）. The effect of RFE on the microstructure and mechanical properties of 6061 aluminum alloys with different aging states was investigated. The results show that the refractory AlFeMnSi phase of 6061 aluminum alloys can be broken by using RFE， resulting in the fine and uniform distribution of the AlFeMnSi phase in the alloy. Under the combined effects of frictional heat and deformation during RFE processing， the pre-precipitated coarse Mg2Si phase is dissolved and re-precipitated， resulting in that the pre-precipitated coarse Mg2Si phase has no effect on the particle stimulated nucleation （PSN） mechanism in the dynamic recrystallization of the material. Therefore， the size of grain exhibits negligible change by RFE. RFE reduces the strength of as-quenched 6061 aluminum alloys， while the strength of 6061 aluminum alloys with a long-term aging state can be increased by RFE. However， there are holes inside the material processed by RFE， which reduce the elongation of the alloys.

The hot deformation behavior and dynamic recrystallization of Al-11.1Zn-2.3Mg-2.0Cu-0.05Sc alloy was explored in the isothermal hot compression test with a temperature range of 653-733 K at strain rate of 10-3 s-1. The microstructural evolution of the studied alloy at different temperatures was analyzed by EBSD technology. The dynamic recrystallization（DRX） critical strain， critical stress， fraction， and average grain size equations were established by linear regression. The results show that the fitted equations can accurately describe the DRX characteristics of the studied alloy during hot deformation.The increase in the deformation temperature enlarges the misorientation angle inside the grains， which facilitates the DRX progress. The distributions of crystal orientation tend to be more homogeneous with the increase in temperatures. Moreover， dynamic recovery is the dominant dynamic softening mechanism. With the temperature change， there are three types of recrystallization mechanisms in the microstructure of aluminum alloy， including discontinuous dynamic recrystallization， continuous dynamic recrystallization， and geometric dynamic recrystallization.

Abstract This study investigated the role of interfacial deformability in bond integrity and strength, particularly in the production of robust joints between harder austenitic stainless steels (SS) during ultrasonic welding. The specimen without the interlayer experienced limited strength enhancement owing to internal cracking from continuous sliding at interfacial temperatures below 0.6 times the melting point (Tm), which is attributed to the limited deformability of the austenitic SS. In contrast, introducing Fe and Ni interlayers between the substrates resulted in a notable increase in the interfacial strength, surpassing 2500 N in the peak load within a reduced welding duration. The correlation between the interfacial strength and the peak temperature suggests that a substantial decrease in hardness below 0.4 Tm is sufficient for extensive bond formation. Moreover, dynamic recrystallization (DRX) led to grain refinement in the Fe interlayer owing to shorter weld durations, whereas grain growth was observed in the Ni interlayer due to higher peak temperatures. Both the Fe and Ni interlayers significantly improved the bonding integrity by accommodating plasticity through the above phenomena without severe damage to the substrates, leading to increase of interfacial strength by 24% (2050 N to 2500 N) and reduction of weld duration by 40% (1.5 s in Fe interlayer). In addition, the fracture position after the lap shear test shifted from the edge of the weld area to the SS substrate.

High entropy alloy (HEA) coatings of Fe0.5CoCrNi1.5Nb0.68Mo0.3 was prepared on 304 stainless steel using laser cladding and subsequently remelted multiple times. The effects of multiple thermal cycles on the phase composition, grain size, microstructure evolution, and corrosion resistance of the coatings are thoroughly investigated. The original coating consisted of face-centered cubic (FCC), Laves, and NbC phases, and the phase composition does not change obviously, but the distribution and microstructure of the phase change significantly after multiple remelting. As the number of remelting times increased, the bar-like eutectic structure decreased while the lamellar eutectic structure became more prominent. Laser remelting induced dynamic recrystallization in the coating, resulting in a transformation from columnar grains to equiaxed grains, and then back to columnar grains. The grain size also changes significantly with different remelting times. Potentiodynamic polarization and electrochemical impact spectroscopy measurements were conducted in a 3.5 wt% NaCl solution to evaluate the corrosion resistance of the coating. The results revealed both the original coating and the once-remelted coating exhibited lower corrosion current density and higher corrosion potential, but the latter had a higher Faraday impedance. Additionally, immersion tests were performed in 10 wt% FeCl3 solution, which demonstrated that the once-remelted coating displayed fine and uniform corrosion pits with shallow depth. This study provides theoretical support for the regulation of microstructure and the optimization of coating performance. Furthermore, the microstructure evolution law discovered in this research is also applicable to additive manufacturing.

A cost-effective, high-performance Mg-2.0Zn-1.5Mn alloy was fabricated using closed forging extrusion (CFE). The results reveal that CFE can promote a dynamic recrystallization (DRX) ratio and enhance the residual dislocation density in deformed grains and subgrains. Grain refinement is achieved through multiple DRX mechanisms, particle-stimulated nucleation, and pinning effects. In addition, the basal texture and precipitation behavior are significantly influenced by pre-forging in CFE. Finally, grain refinement and substantial residual dislocations result in a good combination of strength and plasticity, with the ultimate tensile strength of 400 MPa and elongation of 22.1%, respectively. A novel strategy for regulating the bimodal grain structure is proposed to guide the optimization of the mechanical performance of rare-earth free Mg alloys.

The effect of high strain rate on adiabatic shear susceptibility and microstructures in Al0.4CoCrFeNi high-entropy alloy (HEA) was examined using a split Hopkinson pressure bar (SHPB) and hat-shaped specimens. The results exhibit a clear strain-hardening effect at high strain rates within the experimental range in six specimen groups. The adiabatic shear band (ASB) with an approximately 1 μm wide was formed at 1.05 × 105 s−1 due to thermoplastic instability resulting from adiabatic temperature rise. The central region of the ASB consists of ultrafine and equiaxed recrystallized grains with a typical size of 100 nm. Comparison of metallographic observation and calculation shear voltage-time, the dynamic shear stress-time curves and the dissipation energy, it was found that the adiabatic shear susceptibility of Al0.4CoCrFeNi HEA increases with increased strain rate. The thermodynamic and kinetic calculations indicate that dynamic recrystallization can occur in the shear band based on the rotational dynamic recrystallization (RDR) mechanism.

The basal texture of traditional magnesium alloy AZ31 is easy to form and exhibits poor plasticity at room temperature. To address these problems, a multi-micro-alloyed high-plasticity Mg–1.8Zn–0.8Gd–0.1Ca–0.2Mn (wt%) alloy was developed using the unique role of rare earth and Ca solute atoms. In addition, the influence of the annealing process on the grain size, second phase, texture, and mechanical properties of the warm-rolled sheet at room temperature was analyzed with the goal of developing high-plasticity magnesium alloy sheets and obtaining optimal thermal-mechanical treatment parameters. The results show that the annealing temperature has a significant effect on the microstructure and properties due to the low alloying content: there are small amounts of larger-sized block and long string phases along the rolling direction (RD), as well as several spherical and rodlike particle phases inside the grains. With increasing annealing temperature, the grain size decreases and then increases, and the morphology, number, and size of the second phase also change correspondingly. The particle phase within the grains vanishes at 450°C, and the grain size increases sharply. In the full recrystallization stage at 300–350°C, the optimum strength-plasticity comprehensive mechanical properties are presented, with yield strengths of 182.1 and 176.9 MPa, tensile strengths of 271.1 and 275.8 MPa in the RD and transverse direction (TD), and elongation values of 27.4% and 32.3%, respectively. Moreover, there are still some larger-sized phases in the alloy that influence its mechanical properties, which offers room for improvement. [ABSTRACT FROM AUTHOR]

In the present work, the type, morphology and size of secondary phase particles in a Mg–4Al–2Sn-0.5Ca (ATX420) alloy are tailored through sub-rapid solidification (SRS) and aging treatment before friction stir processing (FSP) to systematically investigate their impact on microstructures and mechanical properties of the FSP ATX420 Mg alloy. The smaller eutectic CaMgSn phase with micro-defects in the as-cast SRS alloy is more likely to be broken during FSP, compared to the as-cast conventional solidification (CS) alloy. Additionally, nano-sized CaMgSn and Mg17Al12 particles precipitate in as-aged SRS alloy due to a high supersaturation solubility of solutes in the as-cast SRS alloy. These densely-distributed nano-sized precipitates in the as-aged SRS alloy increase the processing temperature by 60 °C during FSP, which results in less nano-sized precipitates in the stirring zone and grain growth of the α-Mg matrix. This leads to a decrease in hardness in the FSP-aged-SRS alloy (∼10 HV). Besides, the grain structure evolutions in the stirring zone and transition zone are systematically investigated for understanding the microstructure evolution during FSP in Mg alloys with eutectic phase.

Hot compression experiment was conducted on Gleeble-3800 thermal simulation testing machine to investigate the hot deformation behavior of Cr5 die casting mold steel, with deformation temperatures of 1100–1300 °C and strain rates of 0.01−10s−1. The experimental results indicated that deformation temperature and strain rate have significant impacts on dynamic recrystallization(DRX) of Cr5 die casting mold steel, the critical strain of DRX decreased as deformation temperature increased and strain rate decreased. According to the Arrhenius model, the activation energy for deformation was 427.85 kJ/mol, and the constitutive equation of hot deformation was derived. Validation of high temperature flow stress model showed that the fitted model emerged appreciable accuracy and reliability. The processing map was constructed based on DMM theory, which was concluded that the unstable region is mainly concentrated around the deformation condition of 1300 °C/10s−1. Cr5 die casting mold steel exhibits the best hot processing performance under the deformation condition of 1250 °C/0.1s−1, with an excellent efficiency of power dissipation(η = 0.36) and a lower value of Kernel average misorientation(KAM average = 1.675°). Discontinuous dynamic recrystallization (DDRX) is the main mechanism for recrystallization nucleation and growth during hot deformation of Cr5 die casting mold steel.

Pre-upsetting deformation is an effective way to optimize the microstructure of plastic forming components and achieve deep modification. In this paper, the pre-upsetting deformation of AZ31 Mg alloy billet was carried out before alternating forward extrusion, and the effect of pre-upsetting deformation temperature on the recrystallization behavior and texture evolution of AZ31 Mg alloy formed by alternating forward extrusion was analyzed. The results showed that the strains generated by the pre-upsetting deformation at different temperatures all leaded to a high dynamic recrystallization (DRX) driving force. This results in a high percentage of recrystallized grains in all pre-upsetting alternating forward extrusion (UAFE) formations. The highest percentage of recrystallized grains 94.5% was observed in U2AFE (pre-upsetting deformation at 623 K). The behavior of DRX has a significant impact on both the distribution and strength of texture. In the case of U2AFE, the maximum basal texture strength is 8.65. This is due to the maximum pole density of the deformed texture, which is composed of non-recrystallized grains and is as high as 9.25. In contrast, the maximum pole density of the recrystallized texture, which is composed of recrystallized grains, is only 8.09. Therefore, non-recrystallized grains play a crucial role in the formation of texture in UAFE. This study provides scientific guidance and technical support for the research of high-performance Mg alloy alternating forward extrusion molding technology.

A new near-α titanium alloy Ti-0.3Mo-0.8Ni-2Al-1.5Zr was designed based on Ti-0.3Mo-0.8Ni (TA10). The hot compression tests were carried out at temperatures of 800–970 °C and strain rates of 0.01–5 s−1. The results show that the flow softening phenomenon in the α + β phase region is more distinct than that in the single β phase region. The Arrhenius constitutive models based on strain compensation in the α+β phase region and β phase region were established respectively, and the correlation coefficient between the predicted flow peak stress values and the experimental values reached 0.99365. The hot processing map of the alloy was established, the processing parameters of the peak efficiency: 800 ≤ T ≤ 818 °C, 0.01 ≤ ε˙ ≤ 0.0235 s−1, and 960 ≤ T ≤ 970 °C, 0.01 ≤ ε˙ ≤ 0.0213 s−1. The microstructure evolution and deformation mechanism of the compressed specimens were researched by electron backscatter diffraction (EBSD) technique. There were two nucleation mechanisms for dynamic recrystallization (DRX): sub-grains growth nucleation and high angle grain boundaries (HAGBs) bulging nucleation, the former was continuous dynamic recrystallization (CDRX), and the latter was discontinuous dynamic recrystallization (DDRX). The flow stress in the α+β phase region was softened by CDRX and dynamic recovery (DRV), while the principal deformation mechanisms in the β phase region are DRV and DDRX. The dislocation strain energy and recrystallization ability at different temperatures were quantitatively analyzed by the kernel average misorientation (KAM) and the geometrically necessary dislocation (GND), and the results showed that more complete recrystallization occurred at lower temperature in the α + β phase region. The HCP slip was principally completed by prismatic ⟨a⟩ and pyramidal ⟨c+a⟩ slip systems during the hot compression, while BCC was a mixed mode of {110}, {112} and {113} multiple slips.

The bonding joints of 2219 aluminum alloy with different deformations of 30%, 45% and 55% were fabricated using hot-compression bonding, and subsequent subjected to homogenization treatment. The interfacial microstructure and interfacial oxide evolution of the bonding joints were systematically investigated. The results showed that increasing deformation can effectively reduce the formation of interfacial voids and promote the interfacial grain boundary migration (IGBM). As the deformation increased from 30% to 55%, the flat bonding interface transformed into curved grain boundaries, and ultimately being occupied by dynamically recrystallized (DRXed) grains. The development of IGBM and interfacial DRXed grains is crucial for ensuring high-quality bonding joints. At 55% deformation, the interface bonding strength reached 156.2 MPa, corresponding to 98.1% of the matrix bonding strength. In addition, the residual interfacial oxide film Al2O3 reacted with MgO and transformed into MgAl2O4 spinel. The final evolution products at the bonding interface were the mixture of MgO, Al2Cu, Al2O3, and MgAl2O4. The bonding interface at 55% deformation successfully achieved relatively clean atomic bonding after homogenization. Based on interfacial void closure, interfacial oxide film fragmentation and evolution, and interfacial recrystallization, the bonding mechanism of 2219 aluminum alloy joints was proposed. These findings contribute to our understanding of the interfacial bonding process in metal solid bonding.

On certain occasions, such as bending, a sheet with gradient microstructure may present higher formability compared to one with uniform microstructure. In this study, the formation of gradient microstructure in AZ31 alloy sheets extruded by the asymmetric die is comprehensively investigated. The results exhibit the microstructure evolution undergoes three stages, namely the initial dynamic recrystallization (DRX), abnormal grain growth (AGG), and the secondary DRX. After the initial DRX, the microstructure is fine and uniform, and the transverse direction (TD) preferred texture is formed due to the initiation of non-basal slip. Owing to the high extrusion temperature, AGG occurs after the initial DRX. The grains with basal texture are engulfed by the grains with TD-preferred texture. During the AGG, the grain size is coarsened from 11.4 μm to 382.1 μm. As the material flows through the die bearing, the secondary DRX occurs near the corner of the die. Ascribed to the gradient strain near the bearing, the grains near the bottom surface of the sheet are refined again, while those near the other side inherit the large sizes from grown grains. Ultimately, the extruded sheet exhibits gradient microstructure along the thickness direction, i.e. normal direction (ND). The gradient-distributed plastic strain and strain rate are the main causes of gradient microstructure.

This study explores the plastic deformation mechanism and microstructural evolution of as-homogenized and as-forging Inconel 718 alloy through low temperature and slow strain rate hot compression deformation. The stress-strain curves of Inconel 718 alloy were analyzed by modulating the deformation temperature, strain rate, and strain, and the extreme grain refinement process from cast billets (with abnormally coarse grains) to the final compression sample was revealed. The results show that the true stress levels are lower during both low temperature and slow strain rate hot compression, relative to high temperature and fast strain rate deformation. For the as-homogenized Inconel 718 sample, the same grain refinement as the high temperature and fast strain rate (i.e. forging deformation) was achieved by the low temperature and slow strain rate compression deformation. For Inconel 718 samples after forging, uniform, equiaxed, fine grains with an average size of 2.9 μm are obtained at lower deformation temperatures and slower strain rates. Based on these results this low temperature and slow strain rate metallic forming process demonstrates the potential for the application of plastic deformation in controlling grain size, morphology, and distribution, providing a direct, economical, and efficient approach to achieving fine equiaxed grain structures in as-forging metallic materials.

In this study, the stress-strain behavior of sintered Ti2AlNb alloy obtained at the temperatures of 980 °C and 1080 °C with a strain rate of 0.5 s−1 was investigated using compression tests under furnace heating and current heating. When deformed at 980 °C, the B2 phase texture orientation all exhibited //ND and //ND during current-assisted hot compression (CAHC) and furnace hot compression (FHC). With the deformation temperature increased to 1080 °C, the texture //ND gradually moved towards the texture direction during CAHC. The results were ascribed to the different microstructure evolution that dynamic globularization and DRX by electric current. It indicated that the current promoted the spheroidization of the O phase which did not change the texture orientation. However, as the temperature increased to 1080 °C, the current promoted dynamic recrystallization which resulted in big changes in B2 phase texture orientation. The current promoted the spheroidization of lath by accelerating the phase transformation of O→B2. The current affected the dynamic recrystallization (DRX) mechanisms by promoting the transformation of low-angle grain boundaries (LAGBs) into high-angle grain boundaries (HAGBs) through continuous absorption of dislocations. The true stain-stress curves indicated the reduction of the deformation resistance and enhancement of the deformability of the Ti2AlNb alloy, which was closely related to the microstructure evolution.

Magnesium (Mg) alloys are becoming popular in lightweight manufacturing due to their low density and high specific strength. However, insufficient slip systems result in poor plasticity of Mg alloys at room temperature. Therefore, an ultrasonic energy field combined with thermal field is introduced to assist the deformation of AZ31 Mg alloy to improve its plasticity. Firstly, ultrasonic vibration (UV)-assisted tensile tests at different temperatures (130–150 °C) are conducted to investigate the effect of UV on material behaviour and the activation of dynamic recrystallization (DRX). Then, the influences of UV on the mechanical properties and microstructure of the material at 150 °C are investigated by varying the parameters of ultrasound amplitude, strain rate, and vibration interval. The results reveal that applying UV can activate DRX at a relatively lower temperature compared with that without UV. Superimposing a certain amount of ultrasonic energy on this material at warm conditions reduces flow stress and increases elongation. In the intermittent ultrasonic vibration (IUV) tests, the DRX percentage and elongation first increase and then decrease as the vibration interval increases. The elongation of specimens with appropriate vibration intervals even exceeds that of specimens with continuous ultrasonic vibration (CUV). However, CUV is more effective than IUV in reducing ultimate tensile strength at different amplitudes or strain rates.

This study investigated the formation mechanism of new grains due to twin–twin intersections in a coarse-grained Mg–6Al–3Sn–2Zn alloy during different strain rates of an isothermal compression. The results of electron backscattered diffraction investigations showed that the activated twins were primarily {101¯2} tension twins, and 60° boundaries formed due to twin–twin intersections under different strain rates. Isolated twin variants with 60° boundaries transformed into new grains through lattice rotations at a low strain rate (0.01 s−1). At a high strain rate (10 s−1), the regions surrounded by subgrain boundaries through high-density dislocation arrangement and the 60° boundaries transformed into new grains via dynamic recrystallization.

This study investigated the effect of adding Al–5Ti–1B grain refiner on the solidification microstructure and hot deformation behavior of direct-chill (DC) cast Al–Zn–Mg–Cu alloys. The grain refiner significantly decreased the grain size and modified the morphology. Fine-grained (FG) alloys with grain refiners exhibit coarse secondary phases with a reduced number density compared to coarse-grained (CG) alloys without grain refiners. Dynamic recrystallization (DRX) was enhanced at higher compression temperatures and lower strain rates in the CG and FG alloys. Both particle stimulated nucleation (PSN) and continuous dynamic recrystallization (CDRX) are enhanced in the FG alloys, resulting in decreased peak stress values (indicating DRX onset) at 450°C. The peak stress of the FG alloys was higher at 300-400°C than that of the CG alloys because of grain refinement hardening over softening by enhanced DRX.

The high temperature deformation behavior of vacuum powder forging FGH95 alloy was studied by Gleeble-3800 thermal simulation testing machine. The hot compression test was carried out at the deformation temperature of 1090-1170 ℃ and the strain rate of 0.01-10 s−1. The flow stress-strain curves under the corresponding conditions were obtained. The effects of deformation conditions on the microstructure evolution of vacuum powder forging FGH95 alloy were analyzed by EBSD. After considering the influence of temperature，strain rate and strain on the flow behavior of the alloy，the Arrhenius equation was selected to establish the constitutive model of vacuum powder forging FGH95 alloy，and the parameters of vacuum powder forging FGH95 alloy were obtained. The relationship between material parameters and strain was fitted and the obtained constitutive equation was verified.The results show that the flow stress of FGH95 alloy prepared by vacuum powder forging process decreases with the increase of temperature and increases with the increase of strain rate. The size of recrystallized grains in the deformed microstructure decreases with the increase of temperature and increases with the decrease of strain rate. The error between the predicted value and the experimental value of the flow stress of the vacuum powder forging FGH95 alloy is 6.33%，and the predicted value is in good agreement with the experimental value.

The trade-off between welding and strength loss during dissimilar metals joining has been important for decades. Strength loss minimization is essential for industries. The current study investigates the microstructure clarification in the nugget zone (NZ) of AA7075/AZ31B dissimilar friction stir welded joints with or without ultrasonic vibration (UV) at different tool offset conditions. The reduction of incomplete dynamic recrystallization towards the AA7075 side and its transformation into complete dynamic recrystallization (DRX) were observed through the analysis of the grain microstructure, which showed that ultrasonic vibration improved dislocations and grain boundaries. Texture analysis discloses high-strain texture towards the AA7075 side, whereas less complex stresses texture for the AZ31 side under UV. Moreover, the grain refinement on both sides of the interface also affects the joint tensile strength. The maximum strength was obtained with ultrasonic vibration. The Schmid factor results reveal that the UV has a minor influence on the slip system towards the Al side. Conversely, it activates the twining system towards the AZ31 side. [ABSTRACT FROM AUTHOR]