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In this paper, direct numerical simulations (DNSs) are performed to investigate the deformation and breakup of an elastoviscoplastic (EVP) droplet in a Newtonian matrix under simple shear flow. The two-phase interface is captured by the volume-of-fluid (VOF) method with adaptive mesh refinement technique. The Saramito model (Bingham model coupled exponential Phan-Thien–Tanner viscoelastic model) is used to characterize the rheological behavior of the droplet. The droplet deformation and conformational state are studied with different Capillary numbers Ca, Weissenberg numbers Wi, and Bingham numbers Bi, which represent the surface tension, elasticity, and yield stress of the droplet, respectively. Our results show that droplet deformation occurs at low Ca, while breakup occurs at high Ca. The droplet non-monotonically deforms with increasing Wi and Bi, while is elongated for higher Ca. In addition, three breakup modes (mid-point pinching, transitional breakup, and homogeneous breakup) are reported for EVP droplets, in which transitional breakup disappears due to the influence of high elasticity. The conformational state of the droplet intuitively demonstrates the change of breakup from horizontal shear to vertical breakup. In spite of the fact that the surface tension always inhibits the deformation of droplets, the present work indicates that Bi has little effect on the deformation with high Wi and high Ca, while the influence is obvious at low Wi and Ca. The observed elastic and plastic effects on droplet deformation and breakup are believed to have significant impacts, as yield stress fluids are widely encountered in industrial applications. [ABSTRACT FROM AUTHOR]

The NbTiAlZrHfTaMoW refractory high-entropy alloy (RHEA) system with the structure of the B2 matrix (antiphase domains) and antiphase domain boundaries was firstly developed. We conducted the mechanical properties of the RHEAs at 298 K, 1023 K, 1123 K, and 1223 K, as well as typical deformation characteristics. The RHEAs with low density (7.41~7.51 g/cm3) have excellent compressive-specific yield strength ( σ YS / ρ) at 1023 K (~131 MPa·cm3/g) and 1123 K (~104.2 MPa·cm3/g), respectively, which are far superior to most typical RHEAs. And, they still keep appropriate plastic deformability at room temperature (ε > 0.35). The superior specific yield strengths are mainly attributed to the solid solution strengthening induced by the Zr element. The formation of the dislocation slip bands with [111](10 1 _ ) and [111](11 2 _ ) directions and their interaction provide considerable plastic deformation capability. Meanwhile, dynamic recrystallization and dislocation annihilation accelerate the continuous softening after yielding at 1123 K. [ABSTRACT FROM AUTHOR]

In order to solve the flood discharge problem of both small- and medium-sized warping dams in the Loess Plateau, a stepped spillway scheme, based on an ecological bag, to achieve full-section water flow and energy dissipation has been proposed in this paper. The hydraulic and energy dissipation characteristics of a stepped spillway layout scheme were studied using 3D numerical simulation. As the height of the dams is low and the spillways are short, the research has shown that the traditional single-step layout scheme leads to a low overall energy dissipation rate due to the small amount of energy dissipated in the initial steps. As a result of this, this paper has put forward two kinds of step layout schemes such as the shunt type and the staggered type for the initial steps. Through analysis of the flow state, the pressure distribution, and the total energy dissipation rate, the results have shown that shunt type and staggered type with front step deformation produced an obvious mixing of the water flow, fewer negative pressure areas, and a higher energy dissipation rate. The optimal energy dissipation rate of the staggered type reached 87.75%, and the maximum energy dissipation rate was increased by 27.97%. [ABSTRACT FROM AUTHOR]

Bulk metallic glass composites (BMGCs) containing an in-situ formed metastable β phase (β-type BMGCs) being capable of transforming to martensites, are a promising class of alloys. Nonetheless, the influence of the structural metastability of β phases on the deformation mechanisms of BMGCs remains largely unclear. This, however, is crucial for understanding and optimizing plastic deformability. In this study, three Ti-based β-type BMGCs with nominal compositions of (Ti 0.505 Zr 0.353 Fe 0.028 Be 0.114 ) 100− x Cu x ( x = 1, 5, 8) have been developed, in each of which the β-Ti phase has a different metastability. For x = 8, the β phase precipitates exclusively and does not transform martensitically during deformation. At the lowest Cu content ( x = 1), however, the β phase contains a high density of fine ω phase upon quenching, which hinders the deformation-induced martensitic transformation. β phases in both BMGCs deform plastically by dislocation glide. Only when x = 5 does the β phase undergo the martensitic transformation to α″-Ti due to an appropriate degree of metastability. The reversible phase transformation between β and α″ followed by twinning in α″ on continuing deformation leads to a “double yielding” behavior and results in strong work-hardening capability as well as superelasticity during compression (cyclic loading) tests. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a class of Zr-based bulk glassy alloy with enhanced plasticity. The microstructure of this glassy alloy consists of dispersion of 2–5nm nanocrystallites embedded in the glassy matrix. Under compression, this glassy alloy displays high strength up to 2250MPa together with a large plastic strain of 5.5–14.5%. The improved plasticity is ascribed to the interaction between shear bands and nanocrystallites. [Copyright &y& Elsevier]

In this paper, heterogeneous L1 2 particles were successfully introduced into Ni 38 Co 25 Fe 13 Cr 10 Al 7 Ti 7 MPEA by two-stage aging treatment. Compared with the homogeneous particles, the heterogeneous L1 2 particles strengthened alloy exhibits enhanced strength-plasticity synergy. The tensile elongation is 23.2%, which is higher than all samples with the homogeneous particles, and the yield strength remains at 942 MPa, which is equivalent to the micro particles (972 MPa) with the highest yield strength in the homogeneous particles. Further analysis of the strengthening and deformation mechanisms revealed that precipitation hardening, and heterogeneous deformation-induced hardening were the main factors for the enhanced strength. The deformation-induced layered fracture networks, high-density Lomo-Cottrell locks, and heterogeneous L1 2 particles microstructure characteristics significantly improve the strain hardening ability; GNDs accumulate at the heterogeneous interface to alleviate the stress concentration at the GBs and improve the tensile plasticity of the MPEA with heterogeneous L1 2 particle structure. The heterogeneous L1 2 particle structure obtained through two-stage aging treatment without severe mechanical deformation has attractive engineering application potential. These properties of Ni 38 Co 25 Fe 13 Cr 10 Al 7 Ti 7 MPEA with heterogeneous L1 2 particle structure have important enlightening and practical value. • Designed and prepared Ni 38 Co 25 Fe 13 Cr 10 Al 7 Ti 7 MPEA with heterogeneous L1 2 particles. • Heterogeneous L1 2 particle structure obtained through simple two-stage heat treatment process. • The heterogeneous L1 2 particle reinforced alloy exhibits superior mechanical properties. [ABSTRACT FROM AUTHOR]

Low cycle fatigue behaviors of a 3Re Ni-base single crystal superalloy with the [001] and [011] orientations have been investigated. At 760 °C, both the [001] and [011] specimens fracture along crystallographic planes. However, the results also indicate a large difference in fatigue deformation behaviors of these two oriented specimens, which is reflected in different deformation mechanisms. For the cyclic stability behavior of the [001] specimens, uneven cross-slip and tangled dislocations and continuous stacking faults cause local stress concentration in the matrix and have an influence on work hardening, while the stress concentration is reduced by dislocation pairs and stacking faults shearing γ′ phases. With respect to the [011] specimens, high density matrix dislocations, parallel dislocations and secondary cracks increase resistance to dislocation movement, resulting in cyclic hardening. We discovered continuous stacking faults that have been rarely reported in the low cycle fatigue. Also, these findings might bring about substantial insights that fatigue fracture and deformation mechanisms are responsible for low cycle fatigue anisotropy at intermediate temperature. [ABSTRACT FROM AUTHOR]

• Present a nonlinear analytical procedure based on the multi-layered plate model. • The extended Galerkin method (EGM) is utilized for the simplification of equations and approximate solutions. • In smaller amplitudes, the nonlinear analysis could degenerate into a linear procedure of analysis. • The dominantly linear relationship between the voltage or deformation and frequency with smaller amplitudes is obtained. The fast reduction of the physical size of film bulk acoustic wave resonators as a layered structure implies the intensification of the electric field which can induce large deformation in the functioning state of devices as a circuit element. Consequently, the nonlinear behavior of the resonator and accompanying properties are to be included and evaluated in the development and optimization for performance improvement. With this objective, the nonlinear formulation of a multilayered film bulk acoustic resonator is presented for the analysis of vibration frequencies and mode shapes with the consideration of larger mechanical deformation. The dominantly linear relationship between the voltage or deformation and frequency is obtained to understand the nonlinear behavior and properties which have been subjected to extensive research analytically and experimentally to satisfy the application needs in all modes of communications and network technology. [ABSTRACT FROM AUTHOR]

The stability of body-centered cubic (β) phases and phase transformations of Nb x HfZrTi ( x  = 1, 0.6, 0.4 and 0.2) high-entropy alloys (HEAs) were investigated. Three types of transformations were observed: the β → ω transformation during cooling in Nb0.2 HEA, the deformation-induced β → α″ and β → α′ transformations in Nb0.4 and Nb0.2 HEAs, respectively. This implies that the phonon anomalies, T 1 1/2(110) and L 2/3(111), as the origins of phase transformations in simple Ti, Zr and Hf alloys, also exist in composition-complex TiZrHf-based HEAs. However, the very small fraction of deformation-induced α′/α″ martensite in fractured Nb0.4 and Nb0.2 suggests a sluggish effect of transformation as compared with simple β-Ti alloys. [ABSTRACT FROM AUTHOR]

Atomic-structure evolution is significant in understanding the deformation mechanism of metallic glasses. Here, we firstly find a dual-step atomic strain variation in laser-shock-peened (LSPed) metallic glasses during compression tests by using in-situ synchrotron X-ray diffraction. Under low compressive load, LSP-deformed zone's atomic-structure shows low Young's Modulus ( E ); with load increase, atomic-structure are re-hardened, showing high E . An atomic deformation mechanism is proposed by using flow unit model, that LSP could induce interconnected flow units and homogenize the atomic-structure. These interconnected flow units are metastable and start to annihilate during compressive loading, causing the dual-step atomic strain variation. [ABSTRACT FROM AUTHOR]

• A novel Zr 45 Ti 15 Nb 20 Ta 20 RCCA with a single-phase BCC structure was developed. • The tensile yield strength and elongation of this alloy are 1087 MPa and 11.8%, respectively. • This alloy has higher specific strength (137 MPa⋅g−1⋅cm3) than other RCCAs containing Ta. • The dislocation-dominated deformation provides the strain-hardening capability. A high specific strength (∼137 MPa⋅g−1⋅cm3) Zr 45 Ti 15 Nb 20 Ta 20 refractory complex concentrated alloy (RCCA) with fine grain size (∼20.42 μm) was investigated. The as-cast alloy exhibits a stable BCC structure with a yield strength is ∼1087 MPa and elongation of ∼11.8 %. The activation of multiple slip systems and the deformation dominated by cross-slip make the alloy have excellent plastic deformability. The dislocation-dominated deformation provides strain-hardening capability on the room temperature (RT) tensile deformation. The discovery of this novel alloy provides a new RCCAs design strategy to meet the actual needs of different scenarios. [ABSTRACT FROM AUTHOR]

To improve the fatigue wear resistance of gray cast iron (GCI), GCI samples were modified by a laser to imitate the unique structure of some soil animals alternating between soft and hard phases; the hard phase resists the deformation and the soft phase releases the deformation. Using the self-controlled fatigue wear test method, the fatigue wear behaviors of treated and untreated samples were investigated and compared experimentally. The results show that the bionic non-smooth surface obtains a beneficial effect on improving the fatigue wear resistance of a sample, and the fatigue wear resistance of the bionic sample assembled with reticulate units (60°+0°), whose mass loss was reduced by 62%, was superior to the others. Meanwhile, a finite element (FE) was used to simulate the compression and the distributions of strain and stress on the non-smooth surface was inferred. From these results, we understood that the functions of the bionic unit such as reducing strain and stress, and also obstructing the closure and propagation of cracks were the main reasons for improving the fatigue wear property of GCI. [ABSTRACT FROM AUTHOR]

The tensile properties and deformation behaviors of Zr based metallic glass composites containing different tungsten fiber orientations were investigated. The angles ( θ f ) between tungsten fiber orientation and loading axial direction are 0°, 15°, 30°, 45°, 60°, 75° and 90°, respectively. The results show that the strength and the failure modes vary with θ f . The tensile strength of the composite decreases as the θ f increases. The tensile strength of the composite at θ f =90° is only 253 MPa. The plasticity of all the composites do not be improved. The composites failed approximately 90° normal fault at θ f =0°/15°, while the composites failed along the tungsten fiber when the θ f is bigger than or equal to 30° because of the low axial grain boundary strength of the elongated W grains. [ABSTRACT FROM AUTHOR]

Abstract: The deformed-induced microstructure evolution and phase transformation behavior of Ti-based amorphous alloy composites (AACs) containing ductile dendrites in situ formed during solidification were investigated using ex situ transmission electron microscopy (TEM) and in situ high-energy X-ray diffraction (HE-XRD). In situ synchrotron-based HE-XRD experiments provide clear evidence on the deformation-induced phase transformation from β to α″ martensite initiated already in the linear elastic stage of the macroscopic stress–strain curve. Detailed analyses from the diffraction experiments show that the grains that were aligned with [001]β along the loading direction (LD) were then easily transformed into α″ martensite, whereas the martensitic variants oriented with [100]α″ along LD were preferentially formed under compression. The current study provides quantitative information about changes in various microstresses between the crystal phase and the amorphous matrix during deformation. Enhancement of the macroscopic plasticity of the AACs was mainly attributed to the strain relaxation in the β phase and to the formation of multiple shear bands in the amorphous matrix triggered by the deformation-induced phase transformation inside β, knowledge of which greatly deepens understanding of the complex micromechanical behaviors in advanced AACs. [Copyright &y& Elsevier]

Abstract: The compressive deformation behaviors of Zr-based metallic glass composites containing different tungsten fiber orientations were investigated. The angles (θ f ) between tungsten fiber orientation and loading axial direction are 0°, 15°, 30°, 45°, 60°, 75° and 90°, respectively. The results show that the strength, plasticity and the failure modes vary with θ f . At θ f =0°, the composite possesses the highest strength and the largest plasticity. When θ f are 45° and 90°, the composites show relatively low compressive strength and plasticity. At θ f ≥15°, the composites fail in different shear modes. The composites fail by in-plane sliding at 0°<θ f ≤45°, while the composites fail by out-of-plane sliding at 45°<θ f ≤90°. [Copyright &y& Elsevier]

Abstract: The millimetre scale W balls reinforced Zr-base bulk metallic glass composite was prepared using infiltration technique. The compressive deformation behaviours of the composite at two strain rates of 1×10−4 s−1 and 1×10−2 s−1 were investigated. The enhanced plasticity is attributed to the effect of W balls, which constrain shear bands propagation and promote the formation of multiple shear bands. The properties of the composite depend evidently on the strain rates. The high strain rate leads to the higher strength and larger plasticity. [Copyright &y& Elsevier]

Abstract: New Zr-based metallic glass/porous SiC interpenetrating phase composites were prepared by water quenching after pressure infiltration. Microstructural investigations conducted by scanning electron microscopy and X-ray diffraction show that the voids of the porous SiC preform were filled with the melt which was quenched into an amorphous state during subsequent solidification. Both the metallic glass and the porous SiC exhibit a three-dimensional interconnected net structure. The fracture mode of the composites under quasi-static compression changes from a shear mode to an axial splitting mode with the increase of the SiC volume fraction from 51% to 82%. The significant difference was present in the fracture morphologies of the composites with various volume fractions of the SiC preform. The stresses concentrated in the phase ahead the interface inflections are proposed to be responsible for the transformation of the compressive fracture mode. [Copyright &y& Elsevier]