Ductile Materials Research Articles

Low-cost, soluble, and highly ductile Mg–Bi–Ca alloy prepared by extrusion and annealing

This study investigates the formation of a high-potential Mg2Bi2Ca phase in MgBixCa2.5x (x = 0.15, 0.22, 0.37 at.%). The rate of degradation can be increased by exploiting the electrochemical corrosion formed between this phase and the magnesium matrix, while the presence of this phase also improves the dynamic recrystallization process of the alloy during extrusion-induced deformation, thereby enhancing its plasticity. The MgBi0.15Ca0.37 alloy exhibited the best comprehensive mechanical properties after annealing, with a yield strength and a tensile strength of 170 MPa and 225 MPa, respectively, and an elongation of 32.9%. Moreover, it recorded a higher increase in the rate of degradation, 150%, at 25 °C than the extruded state. We also investigated the mechanism of influence of the content, distribution, and morphology of the Mg2Bi2Ca phase in the alloy on its mechanical and degradation-related properties. The work here provides insights into the development of highly ductile and low-cost candidate materials for fracturing tools.

Comprehensive analysis of the structural, elastic, electronic, optical, and mechanical properties of orthorhombic CS(NH2)2 under pressure: A first-principles approach

This study provides a comprehensive theoretical assessment of the orthorhombic compound CS(NH2)2, examining its properties under varying pressure conditions. Employing the ultrasonic plane wave pseudopotential technique, first-principles calculations were conducted within the density functional theory (DFT) framework using the Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation (GGA) exchange-correlation functional. The study evaluates the compound's structural, elastic, electronic, optical, and mechanical properties. Simulations with hydrostatic pressure up to 20 GPa reveal changes in structural properties, elastic constants, and mechanical properties. The study estimates material brittleness and ductility based on Poisson's ratio and the B/G ratio. Elastic anisotropy is analyzed using various anisotropy indices. The compound exhibits a direct band gap along the (Z - Z) direction up to 2 GPa, transitioning to a direct band gap along the (U - Z) direction under higher pressures. Additionally, the band gap decreases from 3.817 eV to 2.38 eV as pressure increases from 0 GPa to 20 GPa. Optical properties are investigated by calculating dielectric functions, absorption coefficient, conductivity, reflectivity, and refractive indices for photon frequencies up to 40 eV. The HOMO-LUMO energy gap is estimated at approximately 5.548 eV. Hirshfeld surface analysis indicates significant contributions to crystal packing from interactions such as H···S/S···H (48%), H···H (35%), H···N/N···H (7.8%), and C···H/H···C (5.1%). This research presents the first quantitative theoretical prediction of the elastic, electronic, and optical properties of CS(NH2)2, contributing to our understanding of its behavior under pressure. Although experimental confirmation is required, these findings significantly advance the existing knowledge on the compound's properties and behavior under pressure.

Crack tip plastic zone shape for anisotropic material subjected to mode -I loading

This paper discusses the effect of anisotropy in terms of anisotropy ratio on ductile materials subjected to mode-I type of loading. Thin plate with plane stress condition is considered for this work. σ3 is taken as zero. For considering the effect of Poisson’s ratio, σ3 = ν (σ1 + σ2) is considered. Isotropic plane strain and anisotropic plane stress condition is considered to develop mathematical relations for stress triaxiality and plastic zone around the crack tip by using Hill – von Mises’s yield criterion. The effect of poisons ratio, anisotropy ratio and stress triaxiality is shown on the size of plastic zone around the crack tip. The results were generated and are compared in the form of polar plot for plane strain condition at different Poisson’s ratio. In addition to this, the effect of anisotropy ratio on stress triaxiality is also investigated. It was observed that increase in Poisson’s ratio causes significant reduction in the size of plastic zone around the crack tip. The increase in anisotropy ratio also shows the same trend, especially for its higher values. It is observed that anisotropy plane stress problem of fracture is almost equivalent to isotropic fracture in plane strain condition.

Computational insight into the fundamental physical properties of ternary ABCl3 chloroperovskites compounds using the DFT approach

In this research, the ternary non-centrosymmetric chloroperovskites compounds of the form ABCl3 (A = Rb and B = Be, Mg) are investigated extensively to predict the structural, mechanical, and optoelectronic properties with DFT incorporated in WIEN2K code. The crystalline structure of interested chloroperovskites is identified to be cubic, non-centrosymmetric, and stable. The elastic constants Cij, bulk modulus, criteria of Pugh ratio, and the Born criteria confirm the ductility and mechanical stability of ternary RbBeCl3 and RbMgCl3 materials. Electronic properties such as the band structures and density of states are examined with the most widely recognized TB-mBJ potential approximation. RbBeCl3 shows semiconducting behaviour with an indirect wide band gap energy of 3.74 eV from R-Γ symmetries points, while RbMgCl3 is assumed to be an insulator that possesses indirect wide band gap energy of 6.28 eV from R-Γ. It is identified that the ABCl3 (A = Rb and B = Be, Mg) non-centrosymmetric compounds change the behavior from wide band gap semiconductors to perfect insulators when the ‘B’ site in ABCl3 varies from ‘Be’ to ‘Mg’ element. In the electromagnetic range from 0 eV to 40 eV of incident photons energy, several parameters in optical properties that includes the dielectric function, refractive index, absorption coefficient, optical conductivity, extinction coefficient, and energy loss function are investigated for the quest of potential applications of interested non-centrosymmetric cubic systems in modern photovoltaic technologies. These outcomes may add inclusive understanding within ultraviolet ranges for photovoltaic applications.

First-principles calculations to investigate structural, electronic, optical and elastic properties of α-Ca3N2

The optoelectronic industry, which has become a cornerstone, requires a semiconductor compound to function as a sustainable and green energy source. In this connection, the present study provides a systematic approach to examine the electronic and optical properties of α-Ca3N2 using the linear combination of atomic orbitals method. The xc-functional BECKE-PBE gives the best results for electronic properties by describing the band gap correctly. The dispersion curve shows that α-Ca3N2 is a semiconductor with an indirect band gap of 1.33 eV along the H-Γ direction. Effective masses of electrons and holes are calculated at the peak of the lowest conduction band and highest valence band, along the Γ- direction. Calculation for optical properties has been performed using coupled-perturbed Hartree-Fock scheme for static values and phonon spectrum calculations are performed for dynamic dielectric functions. Further, frequency dependent electron loss function and reflectivity are determined from the dielectric functions. The elastic constants are estimated and elastic moduli are determined. Bulk modulus of 80.6 GPa and Poisson’s ratio of 0.275 reveals that α-Ca3N2 is a hard and ductile material. The characteristic properties of α-Ca3N2 make it a suitable candidate for optoelectronic applications.

ZK61m magnesium alloy plate thickness effect on the impact characteristics of blunt projectiles experimental and numerical simulation studies

To study the impact resistance of ZK61m magnesium alloy plate, firstly, impact experiments were conducted on magnesium alloy plates of different thicknesses using a one-stage gas gun system to obtain the ballistic limit velocity (BLV) and failure mode of the target plate. In addition, the velocity of the punch plug was analyzed by the squeeze chisel block velocity model. Finally, the corresponding numerical simulations were carried out using the Lode parameter-independent MJC fracture criterion and the Lode parameter-dependent MMC fracture criterion, and the influence mechanism of the Lode parameter on the numerical simulation results was analyzed. The results show that under the impact of the blunt projectile, different thicknesses of target plates mainly occur shear plug failure, the BLV first tends to flatten and then increases sharply with the increase of its thickness. Besides, in the same velocity interval, the plugging velocity decreases with the increase of the target plate thickness; the Lode parameter has an obvious influence on the simulation results, which the MMC fracture criterion is more consistent with the experimental results. However, with the increase of the target plate thickness, both MMC and MJC fracture criteria show the phenomenon of overestimation of the material ductility.

Enhanced strength-ductility synergy of laser powder bed fused Inconel 718 via tailoring grain structure and precipitates

Inconel 718 fabricated by laser-powder bed fusion (L-PBF) exhibits a hierarchical microstructure, rendering traditional standard heat treatment processes not entirely suitable. To enhance the tensile properties, a novel heat treatment strategy to simultaneously tailor the grain structure and precipitates of L-PBFed Inconel 718 is proposed. This study aims to investigate the effects of homogenization time, coupled with water cooling, on grain structure, precipitation, and room-temperature tensile properties. The results demonstrate that increasing the homogenization time from 1 h to 4 h results in a significant improvement of tensile ductility by 33.7%, while maintaining higher tensile strength compared to the wrought counterparts. The utilization of water cooling following homogenization effectively suppresses the formation of undesirable δ phases and promotes the precipitation of γ′′ phases during subsequent aging treatment, leading to exceptional tensile strength. Furthermore, the prolonged homogenization time facilitates recrystallization and promotes uniform deformation between adjacent grains, thereby enhancing the material's ductility. This study provides theoretical guidance for the development of customized heat treatment processes to achieve superior mechanical properties in additive-manufactured metallic materials.

Effects of shear bond on quality of Friction stir additive manufactured copper

This study investigates the influence of the shear bond in friction stir additive manufacturing (FSAM) on the quality of printed copper sample. The shear bond is a mixture of thermo-mechanical affected zone (TMAZ) and re-heat affected zone (RAZ), formed around the ultra-fine grain region during FSAM. The shear bond is plays a crucial role in modifying the microstructure and mechanical properties of the printed layers. It is demonstrated that the presence of the shear layer enhances material strength, ductility, and fracture resistance, leading to improved overall quality of the printed samples. The microstructure size of the shear bond is 67.5% smaller than that of copper. This distinctive layer contributes to a notable 20% enhancement in the FSAM sample's performance.

Harnessing Hydrodynamic Cavitation for Surface Modification and Strengthening

Abstract Hydrodynamic cavitation (HC) shows promise for surface modification and strengthening. While previous research has explored its potential for surface hardening and polishing, the application of cavitation for surface texturing remains relatively unexplored. This paper aims to investigate the feasibility of using hydrodynamic cavitation for surface texturing and hardening, as well as identify the key process parameters that influence the outcomes. Computational fluid dynamics (CFD) simulations are utilized to analyze the behavior of cavitation under various conditions, and experimental validation is conducted. The study examines the influence of different chamber insert geometries on cavitation intensity and energy release. It also investigates the effect of process parameters on surface morphology and hardness. The results demonstrate that hydrodynamic cavitation can effectively strengthen specific regions of interest when the cavitation intensity is controlled. However, the formation of surface texture through plastic deformation may be limited to ductile materials or those with low yield strength. The study highlights the significance of utilizing suitable cavitation generators capable of continuously generating cavitation for consistent and controlled intensity. Preliminary results suggest that innovative vortex-based devices have the potential to deliver controlled cavitation intensity to desired areas.

Strengthening mechanism and plasticity deformation of crystalline/amorphous Cu3Fe/Fe3Cu nanolayered composite

Metallic glasses possess high strength and excellent elastic properties due to their amorphous atomic structure. However, they often display brittleness and suffer catastrophic failure because of shear localization, without exhibiting significant macroscopic plastic deformation under tension. In this paper, an effective method to enhance the strength and ductility of metallic glasses is presented by molecular dynamics simulation. The approach involves controlling the thickness of the crystalline Cu3Fe and amorphous Fe3Cu layers. The results indicate that increasing the thickness of the crystal layer improves the strength of the nanolayered composite. The crystalline/amorphous interface impedes stress propagation in the shear transformation zone, thereby enhancing the yield stress of the composite. Additionally, the presence of Hirth dislocations in the crystal layer strengthens the composite. The generation and annihilation of fixed dislocations in the crystal layer cause stress fluctuations in the composite, which further enhances its ductility. However, a small content of crystalline layer can cause stress concentration towards the shear band, leading to rapid fracture failure and reduced ductility. These findings shed light on the plastic deformation behavior of crystalline/amorphous composites at the nanoscale, providing valuable theoretical guidance for designing high-strength and ductile metallic materials.

Influence of Crack Tip Plasticity on the Microstructure and Corrosion Behavior of CA6NM Stainless Steel Measured Using Scanning Electrochemical Cell Microscopy (SECCM)

The existence of cracks within ductile materials such as stainless steel induces local plasticity around the crack tip that may cause local changes in the microstructure. Although the plastic deformation and microstructural heterogeneities are expected to influence the electrochemistry of the area around the crack tip, few are the studies that correlate the factors- strain and corrosion- together.In this work, we analyze the corrosion behavior of pre-cracked CA6NM compact tension stainless steel samples taking into consideration the variations in the microstructure resulting from the local plasticity at the tip of a crack. Multiple surface microstructure analysis are obtained to characterize the surface properties of the plastic zone. The localized corrosion behavior around the crack tip is studied using the scanning electrochemical cell microscopy (SECCM) technique. The acquired micro open circuit potential (OCP) and micro potentiodynamic polarization (PDP) curves were used to generate corrosion potential and corrosion current maps of the scanned area. The electrochemical behavior of the crack tip was compared with that in the un-deformed area of the same sample.The ability to conduct direct electrochemical measurements at microscopic scale through SECCM allows to correlate the localized corrosion behavior to the microstructure analysis obtained before. This work paves the avenue to studying the synergistic effect of fatigue damage on the local corrosion behavior through monitoring both simultaneously.

SUBSTANTIATION OF INDUCTION HEATING DURING FLANGING OF TUBULAR WORKPIECES BY ROLLING FORMING

Rolling forming (RF) processes are among the most efficient methods of metal forming. The required profile of the workpiece in rolling processes is formed by local deformation with conical or cylindrical rolls using sound technological schemes. When roll forming pipe billets with a ratio of the height of the initial deformed part to the wall thickness of more than 2.5, the flange seating process is made impossible by the loss of billet stability with subsequent fold formation. This phenomenon makes it impossible to produce wide flanges by drawing. To form workpieces with particularly wide flanges, we have developed a flanging method by rolling stamping. The essence of the flanging method is that at the initial stages of rolling, the top of the conical roll is shifted in the direction of the contact patch. At intermediate stages, to prevent the workpiece wall from turning inside out, the top of the roll is shifted in the opposite direction (along the workpiece axis). The main technological constraints are imposed by the insufficient ductility of the billet material, which can cause fracture. To develop the flanging processes in a reasonable manner, we studied the mechanics of outer flange deformation and methods of controlling material flow. The stress-strain state (SSS) of the material was analyzed using the hardness measurement method and the mesh method. The nature of the change in the stress-strain state in the most dangerous zones of the workpiece was determined, depending on the ratio of the flange diameter to the initial workpiece. Based on the experimental results, a mathematical model of the deformation trajectory of material particles of the outer surface of the flange in the coordinates of deformation intensity - an indicator of the stress state - was constructed. To assess the deformability of the material, a damage summation model with a power law approximation of the damage function was used. The model allows us to determine the ultimate fracture dimensions of the flange, as well as the plasticity resource used at intermediate stages. The condition for the suitability of metals for flanging by rolling stamping for engineering calculations is obtained. The necessity of applying induction heating in the processes of culling by rolling stamping is substantiated. This makes it possible to expand the technological capabilities of flanging processes by developing and using induction heating of workpieces, due to an increase in the plasticity characteristics and a decrease in the strength characteristics of metals in the process of deformation.

3D Printing of Ceramics with Controllable Green‐Body Configuration Assisted by the Polyvinyl Alcohol‐Based Physical Gels

Additive manufacturing of ceramics has received intense attention. In particular, 3D‐printed ceramics with customized shapes are highly desirable in the chemical industry, aerospace, and biomedical engineering. Nevertheless, developing a simple and cost‐effective process that shapes dense ceramics to complex geometries remains challenging because of the high hardness and low ductility of ceramic materials. Extrusion‐based printing, such as direct ink writing (DIW), often requires supporting materials that pose additional difficulties during printing. Herein, a simple approach is developed to produce stretchable ceramic green bodies of zirconia and alumina for DIW. The ink is composed of polyvinyl alcohol (PVA) and an aqueous suspension of ceramic powders. Besides the colloidal network formed by the ceramic particles, PVA plays an important role in tuning the printability of the aqueous ink. Through a freeze‐thaw process, PVA crystallizes to form physical networks. This strategy provides highly stretchable hydrogel green bodies that can be reprogrammed to complex geometries difficult for common DIW printing. The subsequent drying, debinding, and sintering processes produce ceramics with dense structures and fine mechanical properties. In short, this work demonstrates an efficient method for the DIW of ceramic parts that can be reprogrammed to complex geometries.

Influence of flaw distribution on tensile behavior of Engineered Cementitious Composites (ECC) based on flaw probability model

The high ductility of Engineered Cementitious Composites (ECC) is attributed to the internal fibers’ bridging effect during matrix cracking, where the distribution of strength in components is crucial for ductility design. Starting from fracture mechanics, this paper proposes a method based on the bridging model to convert flaw sizes into fracture strength in an ECC system. The distribution of flaws in the components is implemented using the Weibull function. By incorporating a crack tracing algorithm, the tensile behavior of components under different flaw distributions is calculated. The effectiveness of the proposed model, which considers flaw distribution, is verified through the comparison between the simulated and experimental data. Furthermore, the simulation results indicate that moderate adjustment on the flaw distribution in components can greatly improve the corresponding tensile ductility without compromising the strength. The research outcomes benefit to provide technical supports for the optimization design of material ductility.

Variational sensitivity analysis and shape optimisation applied to a non-local, ductile damage model

AbstractShape optimisation is applied to an elasto-plastic material model with non-local, regularised damage. Geometries of the same volume are generated which behave better under the aspect of damage accumulation. The underlying material model is taken from published literature and enhanced to derive the sensitivities w.r.t the initial reference geometry. A variational approach, together with an enhanced kinematic concept to decouple geometrical and physical quantities, is utilised to derive these sensitivities. With the inclusion of plastic and damaging effects, the load history of the problem has to be taken into account as well. This introduces additional terms for the sensitivity analysis and requires certain adjustments within the numerical treatment. These gradient information can finally be applied in gradient-based optimisation techniques to efficiently solve the stated optimisation problem. The two discussed examples highlight the benefit of damage optimisation. In the first example, a geometry is reshaped to directly reduce the damage accumulation under certain load. In a second example, the results of a compliance based optimisation with the ductile damage material behaviour are compared to shapes resulting from optimisation problems considering elastic and elasto-plastic material behaviour.

Enhanced strength-ductility synergy in high-entropy alloys via architecting three-level gradient hierarchical nanostructure

Gradient microstructural design represents a new strategy for enhancing strength-ductility synergy of high/medium entropy alloys (H/MEAs). However, most of the reported gradient H/MEAs have only one type of gradient microstructure, which has limited ability to realize the full potential of gradient structure. Here, we report a three-level gradient hierarchical nanostructure (GHN) in a Al0.3CoCrFeNi HEA by ultrasonic surface rolling processing (USRP) followed by aging treatment that can result in a six-fold enhancement in yield strength with almost no loss in ductility compared to the coarse structured counterpart. The proposed three-level GHN is characterized with gradient variations in grain size, nano-twin and dislocation density, B2 and σ precipitates content. Systematic experiments indicate that strong hetero-deformation-induced (HDI) hardening associated with the activation of deformation twinning, are responsible for this exceptional strength-ductility synergy. This three-level GHN engineering strategy in this work can also be feasibly applied to many other H/MEAs, and offers an available pathway to develop high strong and ductile metallic materials.

A shortened process of tri-modal microstructure developing in Ti-6Al-4V alloy via electropulsing-induces grain spheroidization

A shortened process combining electropulsing treatment (EPT) and conventional heat treatment (HT) has been applied to develop a tri-modal microstructure in Ti-6Al-4V alloy. The tri-modal microstructure produced by this process has good overall mechanical properties (tensile strength ∼1110 MPa, elongation ∼22.7%). The rapid development of the tri-modal microstructure is attributed to the EPT production of low aspect ratio (LAR) V-poor martensite, which results from the EPT limiting the growth of high-temperature β grains and the diffusion of elements. The α grains decomposed from LAR martensite during the HT process retain a low aspect ratio morphology which can be easily spheroidized. LAR α grains do not undergo phase transformation at two-phase temperature (950 °C) but follow the cylinderization mechanism of spheroidization that relies more on the geometry of the grains than on the high density of dislocation substructures. In this study, the effects of the three types of grains on material strength and ductility are analyzed in detail.

On the impact toughness of amorphous/crystalline metallic laminates

The creation of amorphous/crystalline (A/C) laminated structures offers a promising approach towards the production of damage-tolerant A/C metallic materials. However, constraints in fabrication techniques have resulted in limited explorations into the toughening behavior of bulk A/C laminates. This study scrutinizes the impact toughness of macroscale A/C Ni–P/Ni laminates through instrumented Charpy impact testing. The findings reveal that the thickness of the amorphous Ni–P layer significantly influences the impact toughness of A/C Ni–P/Ni laminates. A/C Ni–P/Ni laminates possessing thin Ni–P layers (1 or 4 μm) demonstrated high impact energy, which was comparable to the monolithic coarse-grained (CG) structure; however, the impact energy decreased with the increasing Ni–P layers thickness. Microstructural characterization of the crack-path profile disclosed that the desired impact toughness in the A/C Ni–P/Ni laminate with a thin Ni–P layer is primarily due to intrinsic toughening induced by plastic deformation ahead of the crack tip, and extrinsic toughening afforded by interface delamination. As the Ni–P layer thickens, brittle interface delamination emerges as the dominant extrinsic toughening source to resist fracture, thereby rendering the A/C Ni–P/Ni laminate vulnerable to impact loading. This work not only elucidates the dependence of toughening mechanism on the Ni–P layer thickness in A/C Ni–P/Ni laminates but also proposes an effective strategy for designing damage-tolerant metallic materials subject to impact loading by incorporating thin, brittle amorphous and thick, ductile crystalline materials to create laminated structures.

Research on bionic flower interaction technology based on linkage mechanism

In this paper we have designed an interactive device of bionic flower based on linkage mechanism by studying the shape and structure of flowers. Firstly, in order to solve the problem of variable morphology of the bionic flower, we have built the internal skeletal structure of the bionic flower in accordance with the working principle of the hinge linkage mechanism; secondly, based on the internal skeletal structure, we have tested a variety of ductile materials, and identified the multifunctional paper material that can be shape-shifting and color-changing; thirdly, we have used the key technology of Arduino to build the intelligent sensors and hardware, and solved the opening and closing sequence and response range of multiplecluster interactive objects. This article research provides new ideas for the display of flower and plant science to the public from the perspective of bionics, and gives new application areas and cultural values to the interactive bionic design of plants and flowers.

Relations of Microstructural Attributes and Strength-Ductility of Zirconium Alloys with Hydrides

As the first safety barrier of nuclear reactors, zirconium alloy cladding tubes have attracted extensive attention because of its good mechanical properties. The strength and ductility of zirconium alloy are of great significance to the service process of cladding tubes, while brittle hydrides precipitate and thus deteriorate the overall performance. Based on the cohesive finite element method, the effects of cohesive strength, interfacial characteristics, and hydrides geometric characteristics on the strength and ductility of two-phase material (zirconium alloy with hydrides) are numerically simulated. The results show that the fracture behavior is significantly affected by the cohesive strength and that the overall strength and ductility are sensitive to the cohesive strength of the zirconium alloy. Furthermore, the interface is revealed to have prominent effects on the overall fracture behavior. When the cohesive strength and fracture energy of the interface are higher than those of the hydride phase, fracture initiates in the hydrides, which is consistent with the experimental phenomena. In addition, it is found that the number density and arrangement of hydrides play important roles in the overall strength and ductility. Our simulation provides theoretical support for the performance analysis of hydrogenated zirconium alloys during nuclear reactor operation.