Yield Strength Research Articles

Effects of cooling process on the microstructure and mechanical properties of a novel high-V high-Mn TWIP steel for cryogenic storage tank applications

In the present work, a novel high-V high-Mn twinning induced plasticity (TWIP) steel for cryogenic storage tank applications was developed. Furthermore, innovative two-stage cooling processes encompassing ultra-fast cooling and the subsequent furnace cooling were proposed. Effects of cooling process on the microstructure and mechanical properties of the experimental steel were investigated. It was observed that with the change in cooling process (the initial temperature of furnace cooling rised gradually), the dwell time of hot-rolled plates above 600 °C was extended. The extension in dwell time facilitated the precipitation of secondary phase particles, leading to the change in average diameter and volume fraction of secondary phase particles. The yield strength increased with the increasing initial temperature of furnace cooling due to the combined effect of small-sized secondary phase particles inside the grains and large-sized ones located at the grain boundaries. The occurrence of intergranular cracking, primarily caused by the presence of large-sized secondary phase particles at the grain boundaries, was the main factor responsible for the significant reduction in total elongation. The small-sized secondary phase particles inside the grains inhibited deformation twinning, while the large-sized ones at the grain boundaries weaken the binding force between grain boundaries, which ultimately resulted in a decrease in cryogenic impact toughness. The implementation of two-stage cooling processes effectively mitigated the trade-off between yield strength and cryogenic impact toughness, offering a novel approach and valuable insights for optimizing the strength and toughness characteristics of cryogenic high-Mn steels.

Impact of in-process cooling and tool rotation speed on the mechanical and microstructural characteristics of friction stir processed AA2024

Despite significant grain size refinement, friction stir processing (FSP) of heat-treatable aluminum alloys is found to degrade the alloys of strength and hardness qualities. The drop in strength brought on by coarsening or the dissolution of the strengthening precipitate(s) could not be made up for by the improvement in strength brought about by the refinement of grain size following FSP. In order to get around this, the current work looks into a practical method of heat rejection from the FSP zone in addition to grain size refinement during FSP of AA2024 to regulate the precipitate evolution. Under natural cooling, air cooling, and CO2 cooling conditions, friction stir processing (FSP) was used to change the microstructure of Solutionized AA2024 at three distinct rotation speeds of 750, 1180, and 1500 rpm (fixed traverse speed of 50 mm/min). The microstructural evolution (through optical microscopy and SEM) and mechanical properties of FSP samples under different conditions of rotation speed and cooling and their differences were mainly discussed. All the FSP samples have a higher Vickers hardness than the base metal (minimum variation of 16.79% and maximum variation of 41.05%). The maximum hardness, yield strength, tensile strength, and elongation have been obtained under air cooling conditions and a rotation speed of 1180 rpm, which is a result of the simultaneous and effective effect of grain boundary strengthening and precipitation hardening.

TiC-induced nanoscale Cu-rich re-precipitation mechanism under welding thermal cycles and its effect on the strength-toughness of heat affected zones

In order to solve the softening problem of welding heat affected zone (HAZ) for Cu-bearing steel caused by the dissolution of Cu-rich particles, TiC was utilized to induce the Cu-rich re-precipitation. With the peak temperature increased from 780 °C (ICHAZ) to 950 °C (FGHAZ), the size of 9R–Cu increases from 4 nm to 5 nm, accompanied with the increment of volume fraction from 0.6% to 1.0%. Phase field simulations indicate that TiC repels Cu atoms into γ-Fe matrix and promotes the formation of Cu-rich clusters. Then, Cu-rich clusters provide more nucleation sites for Cu-rich particles, which contributed to the re-precipitation of refined 9R–Cu. Due to the disappearance of coarse grain boundary Cu-rich particles and formation of fresh lath bainite, re-precipitated Cu-rich particles provided precipitation strengthening value of 237 MPa and 298 MPa without decreasing the low temperature toughness for ICHAZ and FGHAZ. The yield strength and absorbed energy at −40 °C of HAZs exceed 1000 MPa and 120J, respectively.

A comprehensive study on the effects of surface post-processing on fatigue performance of additively manufactured AlSi10Mg: An augmented machine learning perspective on experimental observations

In this study, the efficacy of 21 distinct surface post-processing methods on the fatigue behavior of an additively manufactured (AM) material was investigated. Various treatments, encompassing single-step processes like sand blasting (SB), conventional shot peening (CSP), severe shot peening (SSP), gradient severe shot peening (GSSP), ultrasonic shot peening (USP), severe vibratory peening (SVP), ultrasonic nanocrystal surface modification (UNSM), laser shock peening (LSP), laser polishing (LP), tumble finishing (TF), chemical polishing (CP), electro-chemical polishing (ECP), and machining (M), as well as hybrid treatments, were systematically investigated for their impact on the fatigue behavior of hourglass laser powder based fused (LB-PBF) AlSi10Mg specimens. A comprehensive series of experimental tests were carried out, covering surface texture analyses, microstructural characterizations, porosity measurements, hardness, residual stresses (RS), monotonic tensile tests, and rotating bending fatigue tests at four stress levels. Following the experimental investigations, the acquired data were leveraged to develop a machine learning (ML)-based model to correlate the fatigue life with the influencing factors and conduct parametric and sensitivity analyses. The model utilized a deep learning approach to predict the fatigue response of LB-PBF AlSi10Mg, incorporating various artificial neural networks (ANNs) and considering input parameters such as yield strength, ultimate tensile strength, elongation to fracture, porosity, depth of pore closure, surface hardness, depth of hardness variation, surface RS, maximum compressive residual stresses (CRS), depth of the CRS field, top surface grain size, surface layer mean grain size, surface roughness, and stress amplitude. Depending on the life regime, the factors influencing fatigue behavior can vary significantly. In higher stresses, dominated by plastic strains, surface residual stress emerges as the primary factor. Conversely, in lower stresses, dominated by elastic strains, the significance of surface roughness becomes more pronounced, followed by surface residual stress, surface hardness and other factors. These findings underscore the contextual importance of different influencing factors for enhancing fatigue resistance based on varying loading conditions.

Numerical Simulation Analysis of the Bending Performance of T-Beams Strengthened with Ultra-High-Performance Concrete Based on the CDP Model

In bridge reinforcement projects, damaged T-beams are the most common objects for reinforcement, yet the interface bonding and bending performance of UHPC reinforcement on T-beams have hardly been studied. To ensure the reliability and stability of UHPC-strengthened T-beams in practical applications, this study introduced a post-installed rebar bonding technique to efficiently connect T-beams with UHPC layers. Initially, using ABAQUS software [2020 version] for finite element simulation, this study investigated the effects of various post-installed rebar parameters (horizontal spacing, yield strength, diameter, and matrix concrete strength) on the shear performance of the UHPC and RC interface, obtaining the optimal connection parameters. Subsequently, by comparing shear formulas in domestic and international standards, a new UHPC-RC steel bar interface shear strength theoretical formula with 93.6% accuracy was derived. Finally, finite element simulations analyzed the impact of different post-installed reinforcing bar layout forms and longitudinal spacing, as well as UHPC-strengthened location and layer thickness, on the bending performance of damaged T-beams. The results showed a good match between simulation outcomes and experimental results, applicable for further reinforcement analysis of T-beams. When the horizontal spacing of post-installed rebars is 12d, with diameters ranging from 10 mm to 14 mm, their anchoring capability is efficiently utilized. A square form of a post-installed rebar with a longitudinal spacing of 300 mm effectively improves the ultimate bending load capacity of the strengthened beam. The simulation analysis and theoretical results help in the design and application of post-installed steel connections and UHPC-strengthened structures in UHPC-strengthened reinforced concrete T-beam structures.

Effects of Zr and Y additions on microstructure and mechanical properties of cast A356 alloy

In the present work, the effects of Zr and/or Y addition on microstructure and mechanical properties of cast A356 alloy were investigated using X-ray diffractometer (XRD), differential scanning calorimetry (DSC), optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The heterogeneous nucleation effect on Zr-rich phases generated by the peritectic reaction, the increased constitutional undercooling caused by Y addition and serve as surfactant led to the grain refinement. Besides, The average size of eutectic Si reduced from 8.5 μm in the base alloy to 6.2, 1.3, and 1.7 μm with the addition of Zr/Y/Zr + Y, respectively. Zr can slightly refine eutectic Si due to the limited growth space caused by grain refinement, while Y can modify the morphology of eutectic Si from plate-like into fibrous-like through high density twins formed by the IIT mechanism. The optimal mechanical properties are obtained when Zr and Y are added simultaneously with the ultimate tensile strength, yield strength, and elongation values of 104 MPa, 201 MPa, and 7.6%, respectively. The YS and UTS increase was due to grain-refining, Si modification and precipitation strengthening. The enhancement of El was mainly caused by Si modification, which reduced the possibility of crack initiation and propagation at Si/α-Al interfaces.

Influence of heat treatment on the microstructure and mechanical properties of Al–Mg–Si alloy fabricated by double wires + arc additive manufacturing

Al-3.4Mg-1.7Si alloy single-pass and multi-layer thin wall components were fabricated with double wires + arc additive manufacturing procedure. Heat treatment was performed to further process the component. The microstructure and mechanical properties of the as-deposited and heat-treated components were comparatively investigated. After heat treatment, the grains grow up slightly, and the phase particles change to distribute semi-continuously, and a large number of nanoscale monoclinic β″ precipitated phases generate. The porosity increases to 0.0486% from as-deposited 0.0348%. The microhardness, ultimate tensile strength and yield strength are respectively improved by 25%,79%, and 228% with heat treatment process, with the hardness uniformity and elongation decreased.

Evolution of microstructure and texture and their influence on the strength of an accumulative roll bonded (ARBed) Al-Sc-Zr-Er-Ti alloy

Accumulative roll bonding (ARB) is an effective approach to improve the strength of metal sheets. This work studied the evolution of microstructure and texture and their influence on the strength of an ARBed Al-Sc-Zr-Er-Ti alloy, produced by multi-microalloying Sc, Zr, Er, and Ti into pure Al. A high-quality interface and a fine microstructure with an average grain size of ∼0.6 μm were achieved as by the ARB process. The Dillamore {4411} <11118> and the Copper {112} <111> components were sharpened in final texture as is common in ARB. However, after the 5th cycle, there was a new texture component along the α-fiber, at (φ1, Φ, φ2) ≡ (60°, 45°, 0°) in Euler space. The yield strength (YS) and tensile strength (UTS) increased with increasing the number of ARB cycles. The 7th ARBed Al-Sc-Zr-Er-Ti alloy had increased YS by 45% and UTS by 57%, respectively, compared to the initial cold rolled sheet. Strengthening was mainly attributed to dislocation strengthening, grain refinement and precipitation strengthening. There was little texture strengthening because of a strengthening and softening alternation with the change of ARB cycle.

Nanosized austenite and coherent nanoprecipitates making maraging steel strong and ductile

Here we report a microstructural design in maraging steel, which renders superior strength-ductility synergy by combining the advantages of transformation induced plasticity and dislocation cutting mechanisms, via an economic thermomechanical route suitable for industrial scale. It aims at innovating ductile maraging steel without conceding too much strength. Specifically, a high-strength maraging steel is first treated by cold-rolling and intercritical annealing, which leads to partial retransformation and precipitation of supersaturated needlelike/near-spherical B2-structured nanoparticles occurring simultaneously in dislocated α'-martensite matrix. The material is further optimized by peak-aging, yielding a desired microstructure, with nanosized γ-austenite ( ∼150 nm) dispersed in lath α'-martensite ( ∼130 nm) with dense spherical B2-nanoprecipitates ( ∼6.5 nm), i.e., an austenite-maraging structure with hierarchical heterogeneity at nanoscale. The yield strength is measured to be ∼1.65 GPa, which is largely retained as it combines boundary strengthening, dislocation strengthening and ordering strengthening of nanoprecipitates. Surprisingly, significant work hardening renders an ultimate strength even high up to ∼1.9 GPa and a decent ductility of ∼6-7%, twice that of conventional maraging steels. Interrupted microstructure examination unravels that it is the hierarchical microstructure heterogeneity-induced sequential activation of plasticity-enhancing mechanisms that confers such excellent deformability. At the stage soon after yielding (ε∼1.5-3%), deformation-induced transformation from metastable γ-austenite to α'-martensite imparts a significant strain hardening rate (Θ) up-turning. At the high strain stage (ε>3%), multiple dislocations cutting through B2-nanoprecipitates promotes the interaction and accumulation of dislocations, thereby postponing Θ attenuation and prolonging ductility.

The effect of inhomogeneous microstructures on strength and stress corrosion cracking of 7085 aluminum alloy thick plate

Inhomogeneous microstructures and alloy chemistry along the thickness direction can greatly affect the mechanical and corrosion properties of new generation 7xxx aluminum alloy thick plates. The inhomogeneous microstructure, stress corrosion cracking (SCC) resistance and strength of AA7085 thick plate (160 mm) at T/2, T/4, and surface position using mechanical tests, double cantilever beam (DCB) crack extension tests and electron microscopy experiments. The results show that the ultimate tensile strength, yield strength and elongation of the T/2 position are slightly lower than those of the surface position, but the SCC resistance of the T/2 position is significantly higher than that of the surface position. The reason is that larger discontinuously quench-induced grain boundary precipitates (Q-GBPs), and lower Zn and Mg elemental content of GBPs (including Q-GBPs and age-induced GBPs (A-GBPs)) and grain boundaries (GBs). Furthermore, it is newly found that the mechanical effects of larger-sized low aspect ratio unrecrystallized grains contribute significantly to the excellent SCC resistance of the T/2 position. The large size grain structure makes short-range SCC cracks along the large-angle GB more tortuous at T/2, improving the stress intensity required for sustained crack extension. In addition, the high GB triple junction deflection angle resulting from a low aspect ratio grain structure at T/2 improves the average driving force required for crack extension and drive force reduction after localized crack growth.

Long-term elasto-static compressive loading drives rejuvenation of a metallic glass

The current work focuses on the impact of mechanical protocol which can lead to either rejuvenation or relaxation of metallic glasses (MGs) through elasto-static compressive loading (ECL) treatment. Here we demonstrate that, even after imposing a long-term ECL process, the Zr52.5Cu17.9Ni14.6Al10Ti5 MG subjected to an elasto-static stress of 85% of the yield stress at room temperature shows varying degrees of rejuvenation without any relaxation. The MG undergoes an increasing trend in structural rejuvenation with an increased stored energy and a more disordered structure. Nanoindentation results reveal that the variation of mechanical responses emerges from the complementary effects of the thermal activation process and the structural heterogeneity of glassy phase. The spital heterogeneities can effectively reduce the activation barriers of the shear transformation zones (STZs) and widen their distributions, which will perturb the shear-banding processes from single motion to collective movements, leading to shear band multiplication/branching and an increase in the elastic energy density cut-off. As a result, the plasticity is significantly enhanced and the yield strength is decreased. These findings shed light on that ECL process is an effective way to enhance the structural heterogeneity and the level of rejuvenation of a monolithic MG, which may allow the design of MGs with desirable mechanical properties.

Influence of Bismuth Addition on the Physical and Mechanical Properties of Low Silver/Lead-Free Sn-Ag-Cu Solder

The Sn–Ag–Cu (SAC) solders with low Ag content have been identified as promising candidates to replace the traditional Sn–Pb solder for flip-chip interconnects. This study examines the impact of incorporating Bi element on the microstructure, thermal behavior, and mechanical performance of low-silver-content Sn-1.5Ag-0.7Cu (SAC157) solder alloy. Besides using the conventional cross-sectioned microstructure image, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and tensile stress- strain techniques were used to investigate the microstructure, thermal and mechanical properties after the addition of Bi, respectively. The results demonstrate that adding of Bi could refine the microstructure, optimize the thermal properties, and improve the tensile strength. Meanwhile, the ductility of the solder alloys reduced evidently in comparison to the Sn-1.5Ag-0.7Cu solder. From the microstructural analysis, 0.5wt% Bi addition to SAC157 significantly enhanced the solid solution effect of Bi and refined β-Sn dendrite, as well as extended the eutectic area. Moreover, as the Bi addition increases to 5wt%, finely dispersed bismuth precipitates within the β-Sn matrix, along with an enlarged eutectic area, lead to a remarkable enhancement in both ultimate tensile strength and yield strength. The electrical resistivity was characterized by the four-point probe technique. The results show that the electrical resistivity of Bi-modified SAC157 solder alloy decrease from 13.9 to 9.8 μΩ cm with the addition of 5wt.% Bi. These improvements can be attributed to the solid-solution and precipitation strengthening effects induced by the presence of bismuth. The results confirmed that the developed material is applicable as a potential high strength solder material in the context of advanced interconnecting applications.

Effect of Cu addition on the thermal conductivity and mechanical properties of Mg-Zn-xCu-Ce alloys

Thermal conductivity and mechanical properties of Mg-Zn-xCu-Ce alloys with different Cu contents under low extrusion temperature were systematically investigated in this work. The results shows that MgZnCu and Ce-rich (Mg, Zn, Cu, Ce) phase were formed in Mg-Zn-xCu-Ce alloys with high Cu content, which have significantly effect on the thermal conductivity and dynamic recrystallization (DRX). The distribution of grain morphology and LAGBs indicates that CDRX is the main mechanism. The addition of Cu element has an inhibitory effect on the DRX behavior, greatly refining the DRXed grains. After extrusion, a large amount of nano-phase is dispersed in the MZEC alloy, which has a strong pinning effect on dislocations. The formation of MgZnCu phase with high thermal conductivity sacrifices the solute atoms of Zn and Cu in α-Mg matrix, which leads to reduction of lattice distortion of Mg matrix, thereby ensuring high thermal conductivity of Mg-Zn-Cu-Ce ternary magnesium alloys. With the increase of Cu content, the strength and thermal conductivity of the alloy gradually increases. When the Cu content is 3.6wt%, UTS (ultimate tensile strength), YS (yield strength), EL (elongation) and thermal conductivity are 350 MPa, 317 MPa ,15.8% and 135 W/m∙K, respectively.

Microstructure and properties nonuniformity of Ti6Al4V component fabricated by high-power laser melting deposition

High-power laser melting deposition provides an efficient solution for the fabrication of large-sized titanium alloy components. In this study, Ti6Al4V blocks with well-formed structures were prepared using a 7 kW laser power, and their internal defect distribution, microstructure along the deposition direction, tensile properties, and fatigue performance were investigated. The results showed that the density of the as-deposited Ti6Al4V blocks could reach 99.94%, and the main internal defects were cavities, primarily spherical and dispersed, with a maximum diameter of 326.7 μm. Among them, 65.53% of cavities had a diameter smaller than 100 μm, and 92.76% had a diameter smaller than 200 μm. The microstructure at the top region of the specimen consisted of a needle-shaped α phase, the middle region had a mixture of needle-shaped and lamellar α-phase, and the bottom region showed a lamellar α-phase structure. With an increase in deposition height, the aspect ratio of α-phase increased, and the average width decreased from 3.22 μm to 0.88 μm. The internal structure was mainly composed of a basket-weave structure, with a small amount of Widmanstätten structure present at grain boundaries. Hardness and tensile properties exhibited significant non-uniformity along the deposition height. The tensile strength and yield strength at the top region were approximately 50 MPa higher than those in the middle and bottom regions, while the elongation was about 2% lower. The top region's tensile fracture surface displayed a sawtooth pattern, whereas the middle and bottom regions exhibited fractures along the 45° direction of the principal stress. The length of α-bundles and the interface density within the bundles were crucial factors affecting crack propagation. In the top region, α bundles were the longest, and the interface density was the highest. During crack propagation, when the crack extended perpendicular to the α bundles, it encountered high resistance, and when it extended non-perpendicular, it rapidly propagated along the bundle boundaries, exhibiting high strength and low plasticity. The fatigue performance of the Ti6Al4V specimens fabricated by high-power laser melting deposition showed significant dispersion, with cracks originating from subsurface lack of fusion defects. At different stages of fatigue crack propagation, the role of α phase laths varied: during the fatigue source region, cracks primarily propagated along the boundaries of α laths, displaying significant cleavage fracture characteristics. In the fatigue propagation region, crack propagation velocity was mainly influenced by the direction of the laths, and in the fatigue final rupture region, ductile fracture was predominant. Α laths parallel to the tensile direction exhibited the best plasticity, promoting the formation of large dimples and high tear ridges.

Strengthening Fe1.4Co0.8Ni0.8Cr high-entropy alloy composites via in-situ synthesis of TiC: Perspective from experiments and first principles calculations

Achieving a harmonious balance between strength and plasticity is a long-standing problem in single-phase face-centered-cubic (fcc) high-entropy alloys (HEAs). Herein, in-situ TiC ceramic particle reinforced fcc-structured Fe1.4Co0.8Ni0.8Cr HEAs is designed and investigated by combining the experiments and first-principate calculations. The results show that the y(TiC)-Fe1.4Co0.8Ni0.8Cr (y=0, 2.5, 5.0, 7.5 and 10.0%, y: volume fraction) composites consist of fcc phase with submicron/micron TiC after the co-addition of Ti and C element, and the formation of TiC facilitates to refine the microstructure of the composites. Such microstructural evolutions significantly enhance the mechanical performances of the composites. Particularly, the 7.5%(TiC)-Fe1.4Co0.8Ni0.8Cr composite exhibits a high yield strength of ∼562.7 ± 7.7 MPa and tensile strength of ∼971.3 ± 5.4 MPa, which are respectively increased by 169.0% and 88.3% as compared with the Fe1.4Co0.8Ni0.8Cr based alloy, yet with the fracture elongation decreases to 35.9 ± 0.3%. The increment in yield strength is mainly driven from the combined effect of the grain refinement strengthening, dislocation strengthening and precipitation strengthening. Density functional theory (DFT) results reveal that the increase of C-Ti bonds and the formation of covalent bonds in the 7.5%(TiC)-Fe1.4Co0.8Ni0.8Cr composite lead to relatively higher strength and lower ductility, which are well agreed with the experimental results.

Hybrid interlayer hot rolling and wire arc additive manufacturing of Al-Mg alloy: Microstructure, mechanical properties and strengthening mechanism

Considering the deformation-strengthening benefits of Al-Mg alloy and the high forming efficiency offered by wire and arc additive manufacturing (WAAM), the microstructure evolution and strengthening mechanism of hybrid interlayer hot rolling and wire arc additive manufacturing (HR-WAAM) samples have been systematically investigated in this study. The results indicate that interlayer hot rolling can effectively reduce the size and number of pores, which diminishes the stress concentration areas. Additionally, rolling deformation significantly enhances the effect of dislocation strengthening. Furthermore, a high density of dislocations can promote recrystallization to refine grain size, while also improving grain orientation, all of which contribute to better stress distribution. Due to these reasons, the strength and toughness of the alloy are notably improved. The average ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) values achieved by HR-WAAM samples were 338 MPa, 276 MPa, and 20.9%, respectively. These values represent increases of 28.5%, 41.5%, and 38.4% compared to conventional WAAM samples. These findings are expected to provide an efficient and cost-effective method for additive manufacturing (AM) of deformation-strengthened aluminum alloys.

Enhancing the mechanical properties and osteogenic differentiation of Mg-1 wt.%Ho alloy by tailoring microstructures through extrusion temperatures

This investigation was conducted to explore the impact of extrusion temperature on the microstructure, mechanical properties, and osteogenic differentiation of the as-extruded Mg-1Ho alloy. The Mg-1Ho alloy was extruded at three different temperatures, i.e., 320, 350, and 380 °C, leading to variation in its grain size and texture intensity. With decreasing extrusion temperature, a significant increase was achieved in its room-temperature ultimate tensile strength (UTS) and yield strength (YS). After being subjected to an extrusion temperature of 320 °C, furthermore, Mg-1Ho alloy can effectively promote osteogenic proliferation and differentiation, anti-inflammatory, along with osteogenic gene expression. Our findings emphasized that adding extract from Mg-1Ho alloy extruded at 320 °C enhanced the ability of osteogenesis, demonstrating its potential as a biomaterial to improve cell performance and fate.

Mechanically Controlled Landslide Deformation

AbstractMany landslide models assume a fully deformable body without any resistance against deformation. However, in reality, landslide bodies can display negligible to large deformation during motion. Examples for limited deformation include the prehistoric giant landslides of Flims and Köfels, or the Vajont landslide of 1963, where the structure of rock largely remained intact and the slides did not evolve into rock avalanches. Here, we propose a novel mechanical model for the controlled deformation of landslides. The model is based on the principle of material strength or resistance and includes a user‐specified function that reflects the mechanisms (internal friction, cohesion, viscosity, and yield strength) that act against the deformation induced by the free‐surface or the hydraulic pressure gradient of the landslide. This controls the landslide deformation and, in turn, also the motion and run‐out, and offers a unique possibility to describe the landslide motion ranging from a fully non‐deformable body sliding along the mountain slope to a completely fluidized motion without any resistance against the force associated with the free‐surface pressure gradient. The latter is the situation often considered for the motion of granular flows such as avalanches of snow or rock, or debris flows. The former can play a substantial role in the dynamics, however, has not yet been considered in mass flow simulations, severely limiting the applicability of those models. We demonstrate the performance of the new model and its applicability, also with the advanced open‐source computational mass flow simulation tool r.avaflow.

Effect of temperature on the tensile deformation mechanisms of a fourth nickel-based single crystal superalloys

This work conducted tensile experiments from room temperature to 1100 °C on a new fourth-generation single crystal superalloys along [001]. The effect of temperature on the tensile properties and deformation mechanism of the alloy were investigated. Results showed that the yield strength of the alloy reached its peak value (1017 MPa) at 850 °C. From room temperature to 760 °C, the occurrence of stacking faults (SFs) was observed in the γ matrix channel. From the room temperature to 850 °C, the occurrence of stacking faults was observed in the γʹ phase. The interface dislocation networks appeared at 980 °C and above. At room temperature, stacking faults sheared γʹ phase, in which three types of stacking faults occurred, which controlled deformation process. The main deformation mechanism from 650 °C to 850 °C was the shearing of γʹ phase by stacking faults and super dislocations, and at 850 °C, stacking faults in different directions of propagation corresponded to the formation of Lomer-Cottrell locks (L-C locks), which greatly increased the yield strength. At 980 °C and 1100 °C, dislocation climbing and bypassing and anti-phase boundary (APB) coupled dislocation pair shear γʹ phase became the main deformation mechanism.

Nanocrystallization and strengthening of Mg-Dy-Zr alloys by room temperature rotary swaging

In this study, bulk Mg-Dy-Zr alloys with an average grain size of 78.8 nm and a diameter of 12.1 mm were prepared by room temperature rotary swaging (RTRS). The evolution of the microstructure and texture during the grain refinement process was investigated using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results show that the original texture consisting of arbitrarily oriented recrystallized grains and ED∥[10 0] deformed grains is transformed into an ED∥[10 0] texture after the alloy processed by RTRS. The formation of nanograins is induced by a large number of tensile twins, deformation bands, and dislocation arrays synergistically adapting to the strain. The yield strength and ultimate tensile strength of the nanograin alloys obtained are substantially increased to 281% and 190% of those of the as-extruded alloys. The strength improvement of the alloys is a result of the combined effect of grain refinement and dislocation strengthening, in which nanograin strengthening dominates.