Schmidt Factor Research Articles

Corrosion resistance and wear behavior of CoCrFeNiMn@Gr high entropy alloy-based composite coatings prepared by laser cladding

In this study, we utilize laser cladding to apply a CoCrFeNiMn HEA with 2 wt.% few-layer graphene (Gr) coating onto the surface of Q235B mild steel. Alcohol stirring method was used for HEA and Gr preparation of composite powder. Raman spectroscopy and energy dispersion spectroscope (EDS) indicate the successful mixing of HEA and Gr powders, with Gr adhering to the surface of the HEA powder in a lamellar structure. The X-ray diffraction (XRD), scanning electron microscope (SEM), EDS, and Electron backscatter diffraction (EBSD) analyses revealed that grain refinement and the formation of fine carbide-hard phases in the HEA/Gr coating improve microhardness and wear resistance. The average Schmidt factors of the coating decreased from 0.47 to 0.45 with the addition of Gr, indicating enhanced resistance to plastic deformation and anisotropy. Nanoindentation experiments demonstrated that the HEA/Gr coatings exhibit superior resistance to plastic deformation, effectively enhancing the coating’s durability against spalling under stress and wear conditions. The microhardness of the HEA/Gr coating increased by 99.25%, and the wear rate decreased by 86.31% compared to the HEA coating alone. The open circuit potential (OCP), linear polarization curve, Tafel curves, electrochemical impedance spectroscopy (EIS), and Mott-Schottky tests all indicated that the HEA/Gr coating possesses superior corrosion resistance. X-ray Photoelectron Spectroscopy (XPS) results suggest that the passivation film of the HEA/Gr coating, which contains more oxides and less hydroxide, is more protective and denser, thereby slowing the corrosion rate.

Steady and periodical heat-mass transfer behavior of mixed convection nanofluid with reduced gravity, radiation and activation energy effects

Significance of this study is to explore Arrhenius activation energy, microgravity, chemical reaction and porous medium effects on Darcy nanofluid over a stretching sheet with nonlinear thermal radiations. Purpose of this study is to enhance the lubrication efficiency, excessive heat reduction, surface roughness and tool wear in drilling, milling, grinding and cutting tools of machining procedures. Use of Brownian and thermophoretic nanoparticles in base liquid is very effective to reduce friction in tool-chip and tool-work interfaces, tool life ability and cooling ability through nanofluid minimum quantity lubrication in machining operations. A refined mathematical model is solved using dimensionless variables; oscillatory stokes conditions and primitive variables. The implicit form of finite difference method is applied for numerical results using Gaussian elimination approach. The numerical and physical outputs are secured using Gaussian elimination methodology in FORTRAN tool and TecPlot-360. Graphs are displayed by using numerical data in Tecplot-360 program. Impact of activation energy (AE), solar radiation (Rd), microgravity (RG), porosity (Ω), thermophoresis (NT), chemical reaction (Kr), Prandtl (Pr) and Schmidt factor (Sc) on oscillating frequency of heat and mass transport is depicted. Amplitude in fluid velocity, surface temperature and volume of concentration is enhanced as radiation, microgravity and activation energy increases. It is noted that the increasing amplitude in fluid velocity, temperature and fluid concentration is found with activation energy, radiation and buoyancy force effects. Steady behavior of skin friction and mass transport decreases as Darcy porous medium and reaction rate decreases. Frequency of oscillating skin friction and oscillating heat transfer increases as Schmidt and Prandtl coefficient increases. Fluctuations and amplitude in the frequency of heat and mass transport enhances as thermophoretic nanoparticle enhances.

{10-12} twinning transfer behavior in compressed high-purity hafnium

The interaction between twins and grain boundaries (GBs) significantly influences material deformation and fracture behavior. In the present study, high-purity hafnium (Hf) was subjected to compression at both room temperature and under liquid nitrogen cooling conditions. Twinning transfer (TT) behavior of {10–12} <−1011> extension twin was thoroughly and statistically investigated. Results show that compression temperature affects the misorientation angle (MA) for TT. Under room temperature compression, twins can transfer across GBs with MAs below 30° and partially transfer across GBs with MAs between 30° and 50°. When compressed under liquid nitrogen cooling, twins can traverse the GBs with MAs below 40° and partially traverse the GBs with MAs above 40° and with a maximum MA of 77°. The MA, Schmidt factor (SF) value, and geometrical compatibility parameter m’ of twinning systems in neighboring grains influence the TT. Favorable conditions for TT include low MAs, high SF and m’ values. Stress concentration caused by incoming twins can be alleviated through TT with high m’ at GBs with low MAs. For GBs with high MAs, stress concentration can also be alleviated through TT or twinning-slipping transfer with high m’. Extension and growth of outgoing twins contribute to further stress concentration relief.

Study on the Plastic Deformation Mechanism of Void‐Containing Twin‐Crystal Magnesium with Symmetric Tilt Grain Boundary Angles

AbstractA twin‐crystal magnesium (Mg) model with 9 different symmetric tilt grain boundary (STGB) angles (20°–80°) with preset nanohole defects is established by atomsk and lammps software. The mechanical behavior of grain boundary (GB) angles on twin‐crystal Mg with cavity defects and its cavity evolution are simulated by the molecular dynamics method with embedded atomic potential, and the plastic deformation mechanism is revealed. The results show that the yield stress decreases with the increase of the STGB Angle during the stretching process. When the GB Angle increases from 20° to 80°, the yield stress decreases from 2.28 to 1.42 Gpa. This is because the larger the STGB Angle is, the larger the Schmidt factor is, and the easier it is to start dislocation slip during the stretching process. On the other hand, the larger the Angle of STGB, the more the number of atomic voids at the interface, and the more the number of dislocation nucleation points. The larger the Angle of STGB, the lower the strength of twinning Mg but the better the plasticity to avoid fracture. The plastic deformation mechanism mainly includes the nucleation of Shockley incomplete dislocation at STGBs, dislocation slip generates stacking faults (SFs), GB migration, and base plane dislocations.

Significant reduction of anisotropy in stress relaxation aging and mechanical properties improvement for 2195 Al-Cu-Li alloy subjected to plastic loading

Although the plastic loading can enhance creep deformation and yield strength, the anisotropic Stress Relaxation Aging (SRA) behavior and mechanism under plastic loading remain unclear, which presents a significant challenge in accurately shaping aluminum alloy panels. In this study, the SRA behavior of 2195-T4 Al-Cu-Li alloys were thoroughly studied under initial loading stresses within the elastic (210/250 MPa) and plastic (380/420 MPa) ranges at 180 ℃ by stress relaxation and tensile tests as well as microstructure characterization. The findings reveal that compared with those under elastic loadings, in-plane anisotropy (IPA) values of the stress relaxation amount, yield strength and fracture elongation under plastic loadings are reduced by 60%-80%, 70%-90% and 72%-89%, respectively. Similarly, IPA values of precipitate size in grains and Precipitation-Free Zones (PFZ) width at grain boundaries under plastic loading decrease by 31.4% and 94.4% respectively. These results indicate plastic loading significantly weakens the anisotropic SRA behavior, owing to numerous uniformly distributed fine T1 phases and small IPA values of both T1 precipitates size and PFZ width in various loading directions. Compared with those of elastic loading-aged alloys, yield strength of plastic loading-aged alloys shows high strength-ductility because of the combined effect of closely dispersed fine T1 precipitates, narrowed PFZ and numerous sheared and rotated T1 phases at different locations during tensile process. The uniformly distributed larger Kernel Average Misorientation (KAM) and Schmidt factor values of the plastic loading-aged alloy, as well as the cross-slip generated, also help to enhance the strength and ductility of the alloy.

Effect of Sn content on microstructure and mechanical properties of Mg-2Zn-1Ca-xSn /Al composite plate

This article explores the effects of different amounts of Sn (1,2,5 wt%) added to magnesium matrix on the microstructure and formability of Mg-2Zn-1Ca-xSn/Al composite plates. The second phase analysis results indicate that Sn element has a significant inhibitory effect on Ca2Mg6Zn3 phase. As the Sn element increases, the Ca2Mg6Zn3 phase gradually disappears, but the number and size of CaMgSn phase increase significantly (5–8μm). The tensile results at room temperature indicate that the composite plate has the highest strength but lower elongation when the Sn content is 2 wt%. It is mainly attributed to the dispersed distribution of small-sized second phases (<1μm), which cause pinning effect on dislocations and lead to dislocation accumulation. Excessive Sn (5 wt%) can promote dynamic recrystallization, resulting in equiaaxial grain distribution. The average Schmidt factor (0.22) of the basal slip is concurrently increased, makes the base slip system easier to start at room temperature. The Mg-2Zn-1Ca-5Sn alloy exhibits obvious softening, leading to a significant reduction in hardness difference between the Mg-2Zn-1Ca-5Sn alloy and the Al alloy. The enhanced feature also facilitates improved coordinated deformation capability and serves to prolong the occurrence of interface delamination in deformation. The Mg/Al composite plate exhibits excellent plastic deformation ability when the Sn content is 5 wt%, the average performance values were 207.52 MPa (UTS), 145.48 MPa (YS) and 17.45 %(EL), respectively. The fracture behavior of the composite plate undergoes a shift from brittle fracture to a combination of ductile and brittle fracture modes, occurring simultaneously. In summary, the incorporation of an optimal amount of Sn content can enhance the plastic formability of Mg/Al composite plates.

The Role of Deformation and Microstructure Evolution on Texture Formation of a TA15 Alloy Subjected to Plane Strain Compression.

In this study, the texture formation mechanism of a TA15 titanium alloy under different plane strain compression conditions was investigated by analyzing the slipping, dynamic recrystallization (DRX) and phase transformation behaviors. The results indicated that the basal texture component basically appears under all conditions, since the dominant basal slip makes the C-axis of the α grain rotate to the normal direction (ND, i.e., compression direction), but it has a different degree of deflection. With an increase in deformation amount, temperature or strain rate, {0001} poles first approach the ND and then deviate from it. Such deviation is mainly caused by a change in slip behaviors and phase transformation. At a smaller deformation amount and higher strain rate, inhomogeneous deformation easily causes a basal slip preferentially arising from the grain with a soft orientation, resulting in a weak basal texture component. A greater deformation amount can increase the principal strain ratio, thereby promoting other slip systems to be activated, and a lower temperature can increase the critical shear stress of the basal slip, further causing a dispersive orientation under these conditions. At a higher temperature and a lower strain rate, apparent phase transformation will induce the occurrence of lamellar α whose orientation obeys the Burgers orientation of the β phase, thereby disturbing and weakening the deformation texture. As for DRX, continuous-type (CDRX) is most common under most conditions, whereas CDRX grains have a similar orientation to deformed grains, so DRX has little effect on overall texture. Moreover, the microhardness of samples is basically inversely proportional to the grain size, and it can be significantly improved as lamellar α occurs. In addition, deformed samples with a weaker texture present a higher microhardness due to the smaller Schmidt factors of the activated prism slip at ambient loading.

Effect of Calefaction and Stress Relaxation on Grain Boundaries/Textures of Cu–Cr–Ni Alloy

The Cu–Cr–Ni alloy is a key material for the manufacturing of connectors, which requires excellent resistance to stress relaxation. However, the inherent correlation among microstructure, texture, and properties is still unclear. In this study, we investigated the influence of calefaction and stress relaxation on the grain boundaries (GBs), textures, and properties of the Cu–Cr–Ni alloy. The results showed that calefaction and stress relaxation had opposite effects on GBs and textures. Calefaction led to a decrease in the proportion of low-angle grain boundaries (LAGBs), an increase in the Schmidt factor (SF) value of the grains, and a transition of texture from &lt;111&gt; to &lt;113&gt;. The grains with higher SF values were more susceptible to plastic deformation, which deteriorated the stress relaxation resistance. By comparison, stress relaxation led to an increase in the proportion of LAGBs, a decrease in SF values of the grains, and a transition of texture from &lt;113&gt; to &lt;111&gt; and &lt;001&gt;. After stress relaxation, the variation trends of the GBs and textures were consistent with those of other plastic deformations, indicating that stress relaxation can be verified by the variations in GBs and textures. Our findings provide a theoretical basis for improvements in stress relaxation resistance of the Cu-based alloys used in connector industry.

The evolution of microstructure and mechanical properties of Inconel 625 alloy fabricated by laser powder bed fusion via novel hybrid scanning strategy

Four innovative hybrid scanning strategies (0° + 67°, 45° + 67°, 67° + 67° and 90° + 67°) of laser powder bed fusion (LPBF) have been proposed to tailor the microstructure and mechanical properties of Inconel 625 alloy for the first time. The experiment results revealed in sample I (0° + 67°) and sample IV (90° + 67°) a gradient structure is formed, progressing from randomly textured slender columnar crystals (001) to randomly textured equiaxial fine crystals, and finally to equiaxial and fine columnar crystals. In samples II (45° + 67°) and III (67° + 67°), isometric and columnar crystals are uniformly distributed throughout the sample. The tensile strengths of samples treated via hybrid scanning strategy in LPBF (sample I: 1270 ± 8 MPa, sample II: 1400 ± 6 MPa, sample III: 1390 ± 5 MPa and sample IV: 1360 ± 5 MPa) surpassed those of conventionally manufactured samples, including Inconel 625 alloy fabricated by LPBF using a single scanning strategy. This superiority can be attributed to the presence of fine grains, elevated residual stress levels, and the formation of stacking faults. The results of the nanoscratch test reveal that the bottom surface of samples I and IV demonstrates superior abrasion resistance in comparison to the top surface, which can be attributed to the higher relative density, finer grain size, lower elastic modulus and lower Schmidt factors in the bottom surface. These findings hold significant implications for tailoring the microstructure and properties of Inconel 625 alloy, especially in the realm of additively manufactured materials featuring heterogeneous structures.

A crystal plasticity based strain rate dependent model across an ultra-wide range

Numerous studies have investigated the strain rate sensitive behaviors of materials, consistently reporting enhanced stress values and increased dislocation density with rising strain rates. Behind these phenomena lies the intrinsic nature of dislocation activity. In this context, we introduce an analysis method within a crystal-plasticity (CP) framework, incorporating molecular dynamics insights for a comprehensive range of strain rates (7.5 × 10−5/s to 5 × 107/s). This approach offers a refined understanding of strain rate sensitive behaviors, mainly influenced by dislocation movement laws and strain-rate-dependent saturation of dislocation density. We elucidate the impact of deformation loading conditions on Schmidt factors and active slip systems, which are also crucial for understanding variations in SRS. Ultimately, this study underscores the CP method's effectiveness in comprehensive SRS analysis, seamlessly integrating experimental observations with theoretical predictions for advanced material characterization.

Crystal plasticity analysis of fatigue crack initiation site considering crystallographic orientation in Ti–22V–4Al alloy

In this study, plane bending fatigue tests were conducted on Ti–22V–4Al alloy, a β-type titanium alloy, to examine the fatigue crack initiation behavior in detail. In addition, the prediction of fatigue crack initiation points was investigated from the perspectives of the Schmidt factor (SF) and crystal plasticity finite element method (CP-FEM). The slip system contributing to fatigue crack initiation can be accurately predicted by assessing the magnitude relationship of SF. Also, this prediction is already indicated in a lot of paper by using out of component of slip activity. However, the location where the fatigue crack will occur can be not estimated by SF on polycrystalline. Therefore, prediction of grains where fatigue cracks will occur could be achieved with high accuracy by constructing a CP-FEM that considers the mechanical interaction of polycrystals and grain boundary. Utilizing advanced methodologies such as CP-FEM and numerical calculation techniques, it is strictly investigated that the factors influencing fatigue crack initiation in polycrystalline materials. Our research concluded the understanding of fatigue crack initiation on polycrystal grains by considering the mechanical interaction of polycrystals and grain boundary.

Research on microplastic deformation of Inconel718 under the conditions of high temperature and high strain rate

The compression experiments of the nickel-based superalloy Inconel718 were carried out with the help of split Hopkinson pressure bar device, and the microstructure evolution law in the compression deformation of the alloy was studied by means of optical microscopy, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Based on the dislocation theory, a three-dimensional discrete dislocation dynamics model is established. By simulating the dynamic evolution of the discrete dislocation, the interaction of the dislocation itself and the formation of the dislocation microstructure were captured, and further explore the microplastic deformation process of Inconel718. The results show that deformation conditions significantly affect the rheological behavior and dynamic recrystallization behaviour. The cross slip of dislocations is closely related to temperature and strain rate, which in turn affect the dislocation configuration. The deformation mechanism of Inconel718 under the conditions of high temperature and high strain rate is jointly dominated by dislocation slip and twin deformation. As the temperature increases, the average Schmidt factor increases, and more dislocation slip systems are activated. As the strain rate increases, the number of deformation twins increases, while the thickness of deformation twins decreases.

Crack generation and propagation mechanism of Mo[sbnd]14Re alloy laser welding

This paper investigates the mechanism of crack generation and propagation in laser-welded joints of Mo14Re alloy plates. The study utilized optical microscopy (OM) and scanning electron microscopy (SEM) to examine the microstructure and morphology of the crack area in the Mo14Re laser-welded joint. Additionally, energy dispersive spectroscopy (EDS) was employed to characterize the elements at the crack defect, while electron backscatter diffraction (EBSD) was utilized to analyze the grain boundary and crystal orientation at the crack defect.The analysis of crack formation and propagation considered various factors, including grain boundary segregation, characteristics of grain boundaries and crystal orientation, and the Schmidt factor. The findings revealed that cracks formed in the weld area exhibited distinct characteristics of brittle fracture along the grain. Notably, these cracks displayed evident carbon and oxygen segregation attributed to the presence of a low melting point eutectic liquid film. The segregation, along with high-temperature compounds on the fracture surface, emerged as the primary factors contributing to crack formation.In the proximity of the crack, there exists a concentration of strain, inducing plastic deformation and thereby facilitating crack initiation. Cracks exhibit a tendency to originate along large-angle grain boundaries and deflect along these boundaries. Owing to the difference in atomic slip characteristics on both sides of the crack, the direction of crack propagation is more inclined to deflect towards grains with a smaller Schmidt factor.

Analyzing dynamic strain aging and yield strength anomaly in IN740H, a nickel-based superalloy comprising low volume fraction of γ′

IN740H, a Ni-based superalloy comprising a low volume fraction of γ′, is a promising material for superheater and reheater components in advanced ultra-supercritical (AUSC) power plants. Here, its tensile deformation behavior across a temperature range of 25–800 °C and strain rates of 10−3 to 10−5 s−1 was investigated. Distinct stress-strain curve serrations, consistent with dynamic strain aging (DSA), were predominantly observed between 400 and 600 °C. At lower temperatures and strain rates, Type E serrations appeared, which transitioned to Type B and then to Type B + C serrations with increasing temperature. At 600 °C, Type B serrations emerged at high strain rates, gradually transforming into Type B + C serrations as rates decreased before disappearing at lower rates. Notably, the alloy displayed negative strain rate sensitivity in the DSA regime. Furthermore, the alloy also showed yield strength anomaly (YSA), wherein the yield strength decreased initially with temperature, followed by an increase above a specific temperature. Fractography reveals a transition from transgranular dimple fracture behavior to intergranular fracture behavior with an increase in temperature. Post-deformation electron backscatter diffraction analysis indicated predominant grain alignment along {100} and {111} planes, such that {111}-oriented grains exhibited a lower Schmidt factor and the formation of fewer sub-grain boundaries. This work comprehensively characterizes DSA and YSA in IN740H in the temperature range relevant to AUSC power plants, thereby providing much-needed information to assess its potential suitability for applications under harsh conditions.

Achieving extraordinary strength-plasticity synergy in AZ91 alloy processed by multi-degrees of freedom forming

Strength and plasticity trade-off in magnesium alloys is a longstanding and crucial issue that significantly limits their application, which strongly relates with microstructure distribution and texture characterization. In this study, multi-degrees of freedom forming (multi-DOF forming) technology is innovatively proposed and first employed on as-extruded AZ91 alloy. Microstructure observation reveals that the bimodal-grained structure including 25.4 % of coarse grains (CGs, ∼20 μm) and 74.6 % of fine grains (FGs, ∼2 μm) in volume fraction is fabricated in the multi-DOF formed AZ91 alloy, which is mainly attributed to inhomogeneous dynamical recrystallization (DRX), i.e., un-recrystallized plays a leading role in CGs and DRX plays a leading role in FGs. Grain orientation analysis indicates that multi-DOF forming technology leads to a significant disappearance of basal texture, bringing out the absolute predominance of prismatic texture with 83.4 % in volume fraction, which is mainly owing to the introduction of large radial-tangential coupling shear deformation and thus efficient activation of non-basal slips in magnesium alloys. Moreover, the Multi-DOF formed AZ91 alloy exhibits high ultimate tensile strength (∼402 MPa) without sacrificing elongation (∼18.1 %), realizing extraordinary strength-plasticity synergy. The high work-hardening capacity resulting from high geometrically necessary dislocations at the interface of CGs/FGs is conducive to the improved strength. The higher Schmidt factor in grains with bimodal-grained structure or non-basal texture dramatically contributes to the enhanced plasticity. Thus, we propose a novel and effective multi-DOF forming technology for achieving concurrent enhancement of strength and plasticity in magnesium alloys.

Wave oscillations in thermal boundary layer of Darcy-Forchheimer nanofluid flow along buoyancy-driven porous plate under solar radiation region

The significant contribution of current mechanism is to explore the periodical and fluctuating results of heat and mass flux of Darcy-Forchheimer nanofluid flow along buoyancy-driven porous plate under solar radiation region. Flow through a Darcy-medium has a wide range of applications such as the use of oil in various hydrothermal transfer control, radioactive nuclear disposal systems, water improvement, and filtration of water. The dimensional model is transformed into non-dimension for scaling factors. The primitive-based transformation is applied on steady and oscillatory parts for smooth algorithm in FORTRAN language machine. The convenient model is again reduced into algebraic pattern by using implicit finite difference method. The numerical and graphical results of velocity, temperature and concentration are executed by Gaussian elimination method. To enhance the frequency and wavelength, the impact of solar radiations, thermophoresis, Brownian movement, Schmidt factor, Prandtl factor, porosity and buoyancy pressure is applied on periodic nanoparticles with Darcy Forchheimer relation. The novelty of this proposal to explore the wave oscillations, amplitude and phase angle of thermal and concentration boundary layer of Darcy-Forchheimer nanofluid flow along buoyancy-driven porous plate under solar radiation region. It is noticed that the prominent wavelength and frequency in thermal and concentration boundary layers is generated under porous and solar radiation region. The significance of temperature variation increases as solar radiation, Brownian motion and thermophoresis increases. It is noticed that heat and mass transport enhances as Darcy-Forchheimer and modified buoyancy force increases. In thermodynamic systems, the Darcy-porous materials is prominent assumption that is employed in many domains, especially clinical science, petrochemical and structural engineering, geography, biochemistry and biological physics, and material science. For energy storage and energy conservation, the Darcy-porous material is required for batteries, fuel cells and super capacitors.

Estimation of the fatigue crack initiation site and life of Ti-6Al-4V alloy for two types of circle and slender crystal grains

In this study, the fatigue crack initiation behaviour and fatigue crack initiation life of the Ti-6Al-4 V alloy, which had circular and slender grains, were quantitatively evaluated based on slip line length and out-of-plane component of Schmidt factor. As the results, in crystal grains where fatigue cracks initiated, the slip system that contributes to crack initiation could be identified by considering the out-of-plane component of the Schmidt factor (SFsinΩ), and the fatigue cracks were initiated by the basal slip of the primally α phase in all specimens. Furthermore, regarding the prediction of the location of fatigue crack initiation, it is clear that the grains that are candidates for fatigue crack initiation could be estimated based on the relationship between the slip line length of the basal slip system that contributes to crack initiation in each grain and SFsinΩ. Finally, the macro fatigue crack initiation life could be estimated using a parameter of P that combines micro crack initiation driving force Pi and micro crack propagation driving force Pp.

Effect of annealing on the microstructure and mechanical anisotropy of Mg/Al composite plate

In this paper, the effects of recrystallization, grain growth and texture evolution on the formability and anisotropy of Mg/Al composite plates were studied by different annealing processes. The results show that the rolled Mg/Al composite plate exhibits obvious anisotropy and poor formability in the rolling directions (RD) and transverse directions (TD), which is the result of the synergistic effect of matrix texture and grain characteristics. Annealing-activated recrystallization can eliminate local shear bands, hardening and other defects formed by rolling, thereby softening the structure and improving the formability of the sheet. The occurrence of recrystallization behavior also makes the bimodal texture parallel to the TD distribution in the Mg matrix transform into the RD-TD surface dispersion distribution, which weakens the strong deformation texture. The Schmidt factor (SF) of each slip system is calculated to evaluate the slip system start-up probability (deformation difficulty) of the material in a certain direction. The results show that the average SF values of matrix slip in RD and TD directions increase after annealing treatment, which makes the slip system easier to start. The tensile test results show that the formability of the composite plate is the best when the annealing temperature is 300 °C. At this time, the ultimate tensile strength (UTS) and yield strength (YS) are small, the elongation (EL) is large and the anisotropy of mechanical properties is the weakest. In addition, the annealing of the composite plate leads to the transformation of the fracture mechanism from brittle fracture to ductile-brittle mixed fracture. In summary, annealing treatment can effectively improve the formability and weaken the anisotropy of Mg/Al composite plates.

Anisotropic behavior of as-extruded 7003 aluminum alloy under quasi-static compression and high-speed impact

The anisotropic behavior of as-extruded 7003 aluminum alloy under quasi-static compression and high-speed impact was studied using samples with axes parallel to extrusion direction (ED) (0° sample), at an angle of 45° to ED (45° sample), and perpendicular to ED (90° sample). The experimental results show that the yield stress of the 0° sample is the highest, while the 45° sample is the lowest. Compared with other samples, the 90° sample is more sensitive to the applied strain rate, which experiences a rapid failure after reaching peak stress under high-speed impact. Under quasi-static compression and high-speed impact, the 0° sample exhibits nearly uniform deformation, while the 45° and 90° samples exhibit anisotropy behavior. Due to the occurrence of adiabatic shear, the plastic deformation anisotropy in 45° and 90° samples under high-speed impact is more significant compared to quasi-static compression. For the 45° and 90° samples, the r values, which characterize plastic deformation anisotropy, decrease from 0.77 to 0.82 under quasi-static compression to 0.46 and 0.40 under high-speed impact. In addition, adiabatic shear bands are observed in all deformed samples under high-speed impact, while only the 90° sample fractures. Due to the significant difference in Schmidt factors along ED and transverse direction (TD), plastic deformation of the 90° sample under high-speed impact is mainly concentrated in TD, while the deformation in ED is very small. The extremely uneven deformation leads to earlier nucleation and faster development of ASBs in TD, causing the 90° sample to fracture under high-speed impact.

Micro-crystallographically revealing the plasticity-evolved behaviors of thick Ti–6Al–4V laser-arc hybrid welded joint

Revealing the plasticity-evolved behaviors is of great significance for developing high-reliability thick Ti–6Al–4V welded joint for deep-sea exploration equipment. This research effort entailed a collaborative utilization of transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) techniques to reveal the evolution behaviors of microstructure, weld texture, and grain boundaries for thick Ti–6Al–4V laser-arc hybrid welded joint with thickness of up to 40 mm. The discerned outcomes of this study underscored that the mixture strategy of large-sized lath martensite, densely entangled dislocations, and dislocations pile up at grain boundaries in distinct welding layers significantly enlarged the inhomogeneous plasticity of thick Ti–6Al–4V welded joint. Besides, the intensified cylindrical-texture within the weld leads to a substantial augmentation in the occurrence of Schmidt Factor concentrations above 0.3, indicative of a larger fraction of grains assuming a soft-orientation. Furthermore, the investigation unveiled an increase in the proportion of low angle grain boundaries demonstrably augmented the distribution density of geometrically necessary dislocations (GNDs) within the welds, which in conjunction with the enhanced cylindrical texture substantially elevated the grains deformability, consequently reinforcing the plasticity of welded joint. This work has provided insights into the evolution behavior of thick Ti–6Al–4V welded joint for greatly improving the plastic properties of welded structure, and substantially enhancing the service safety for deep-sea exploration equipment.