Dislocation activities are crucial in facilitating plastic deformation, even in low stacking-fault energy (SFE) materials that are prone to deformation twinning. The high initial strain-hardening rate commonly observed in low-SFE materials is believed to originate from dislocation slip, as twinning typically occurs at large plastic strains. However, twin boundaries account for a significant proportion of the total boundaries in these materials, and it remains unclear whether twin boundaries can effectively nucleate dislocations. Combining multi-scale and in situ electron microscope characterizations, here we report the discovery of a novel type of prolific dislocation sources, which are nano-sized ridges residing along the borders between different twin variants in low-SFE materials. These sources act as dislocation generators that promote dislocation interaction and accumulation, spreading plastic strain and leading to robust strain hardening at the early stage of plastic deformation. Molecular dynamic simulations indicate that the formation of nano-sized ridge-twin structures is energetically favorable at the junctions between multiple twins, explaining why such structures are ubiquitous in low-SFE materials. Decreasing the SFE can significantly increase the population of ridge-twin boundaries, facilitating dislocation emission and hence strain hardening to sustain the stability of plastic flow. These findings provide new insights into the origin of dislocation plasticity and the high early-stage strain hardening rate in low-SFE materials.

Crystallization kinetics of Cu46Zr40Ti8.5Al5.5 metallic glass is investigated in non-isothermal and isothermal conditions. In non-isothermal condition, the crystallization activation energy is determined using Kissinger's method. Further, activation energy of reported Cu-Zr-Al metallic glasses are compared with Cu46Zr40Ti8.5Al5.5 alloy to understand the effect of Ti addition on crystallization kinetics. Detailed investigation on activation energy through the crystallization process is studied. To understand the influence of nucleation and growth mechanism during the crystallization steps, samples are heated in isothermal conditions at various annealing temperatures in supercooled liquid region to determine the local Avrami's exponent using Johnson-Mehl-Avrami equation. Additionally, small scale mechanical response is noted on metallic glass sample to determine the influence of structure on hardness and elastic modulus. Nanoindentation results showed hardness value of 5.39 +/- 0.09 GPa and Young's modulus of 92.81 +/- 0.52 GPa.

The effect of Si on the martensitic transformation in Ni44Ti50Cu6 and Ni50Ti30Zr20 was investigated in the present study. The martensite transformation temperature of the two alloys decreased with the increase of Si content. In particular, a large decrease was observed for Ni50Ti30Zr20. With the addition of 0.5 at

Herein, we systematically explored how to tailor heterogeneity in the Ni-Nb-(Y, Gd) phase-separated metallic glasses (PSMGs) by carefully constructing a metastable miscibility gap and investigating its effect on the formation of heterogeneous shear band (SB) nucleation sites. The Ni60Nb40-x(Y, Gd)x PSMGs with either Nb-Y or NbGd atomic pair (Delta Hmix=+30 kJ/mol) showed hierarchically phase-separated microstructures at the nanoscale, which can be interpreted based on a metastable miscibility gap. Interestingly, statistical analysis of the initiation of plastic deformation via nanoindentation first pop-in analysis in these PSMGs reveals a unique trimodal distribution, unlike the bimodal distribution in monolithic MGs. This tendency arises from the formation of nanoscale phase boundaries as additional differentiated heterogeneous SB nucleation sites. The homogenously dispersed SB nucleation sites help hinder strain localization and SB propagation. In particular, a PSMG with a nanoscale interconnected structure exhibits homogeneous-like plastic deformation, where neither obvious popins nor distinct surface shear steps are observed in the (nano-)indentation test. We believe this study's results provide an effective guideline for tuning correlative heterogeneity and related mechanical responses in PSMGs, highlighting the importance of tailoring microstructure even in MGs.

Recently, concept for an alloy having both glass forming ability and shape memory characteristics has been newly introduced based on the excellent functional properties of existing NiTi alloys. The physical properties of shape memory alloys (SMAs) fabricated through crystallization of glass precursor can be maximized by suppressing the formation of brittle intermetallic compounds and enabling the formation of nanocrystalline structure. The glass precursor is not only applied to small-sized devices easily, but it is possible to produce products with intricate geometry through thermoplastic forming. In addition, the shape memory effect or superelasticity can be manifested after crystallization. In this paper, typical quaternary NiTi-based SMAs and multicomponent NiTi-based SMAs fabricated using glass precursor are reviewed. Firstly, quaternary doping effects on the physical properties in NiTiCu and NiTiHf-based alloys, such as shape recovery characteristics, martensitic transformation, and mechanical behaviors, are introduced. Secondly, multicomponent SMA systems using glass precursor fabricated via rapid quenching are introduced. Glass forming ability, crystallization behavior and consequent transformation properties are discussed. SMA applications using glass precursors, including the micro/nanoscale manipulating tools which utilizes the unique shape memory properties, and the surface imprinting based on the superplasticity are introduced.

In the present work, we propose a thermodynamic approach to identify glass-forming composition in a biodegradable Mg-Ca-Zn system by optimizing chemical enthalpy (∆ H chem ) and atomic mismatch entropy (∆ S σ / k B ) in the statistically designed configurational entropy (∆ S conf / R ) range. Metallic glass composition obtained is fabricated by using melt spinning technique. Glassy nature of the alloy is confirmed by XRD, DSC and TEM analysis. Furthermore, thermodynamic effects of Zn addition in a Mg-Ca-Zn system on glass-forming ability is systematically investigated. Additionally, localized mechanical behavior of metallic glass is analyzed by nanoindentation test. Compared to reported metallic glasses in the Mg-Ca-Zn system, Mg 50 Ca 7.5 Zn 42.5 exhibits improved hardness and hardness to modulus ( H / E ) ratio.

Zr-Co-Cu-Al based metallic glasses (MGs) are potential material for making surgical equipment due to their ultra-high strength. However, presence of elemental Al in these alloys is not desirable due to biotoxicity. To counter this problem the present study is undertaken to design metallic glass forming composition by replacing Al with Ti. Design strategy adopted is based on thermodynamic modelling by rationalizing the effect of chemical enthalpy and atomic mismatch entropy along with statistically controlled atomic arrangement through configurational entropy. The rapid solidification technique was used to synthesize MG in melt spun ribbon form. The structural nature and glass stability of the ribbon are confirmed by X-Ray diffraction, transmission electron microscopy and differential scanning calorimetry. Corrosion response of the MG is thoroughly investigated using potentiodynamic polarization and electrochemical impedance spectroscopy in a simulated body fluid (SBF) environment. The mechanical property of MG is evaluated using microindentation technique. Improvement in corrosion resistance is observed in all the SBF solutions along with in vitro biocompatibility study using MG-63 cell viability experiment.

Molybdenum (Mo) is used to form a barrier layer for metal wiring in displays or semiconductor devices. Recently, researches have been continuously attempted to fabricate Mo sputtering targets through additive manufacturing. In this study, spherical Mo powders with an average particle size of about 37 um were manufactured by electrode induction melting gas atomization. Subsequently, Mo layer with a thickness of 0.25 mm was formed by direct energy deposition in which the scan speed was set as a variable. According to the change of the scan speed, pores or cracks were found in the Mo deposition layer. Mo layer deposited with scan speed of 600 mm/min has the hardness value of 324 Hv with a porosity of approximately 2%. We demonstrated that Mo layers with higher relative density and hardness can be formed with less effort through direct energy deposition compared to the conventional powder metallurgy.

Background: Exercise is recommended for type 2 diabetes mellitus (T2DM) patients to prevent cardiovascular disease. However, the effects of physical activity (PA) for reducing the risk of heart failure (HF) has yet to be elucidated. We aimed to assess the effect of changes in patterns of PA on incident HF, especially in newly diagnosed diabetic patients. Methods: We examined health examination data and claims records of 294,528 participants from the Korean National Health In-surance Service who underwent health examinations between 2009 and 2012 and were newly diagnosed with T2DM. Partici-pants were classified into the four groups according to changes in PA between before and after the diagnosis of T2DM: continu-ously inactive, inactive to active, active to inactive, and continuously active. The development of HF was analyzed until 2017. Results: As compared with those who were continuously inactive, those who became physically active after diagnosis showed a reduced risk for HF (adjusted hazard ratio [aHR], 0.79; 95% confidence interval [CI], 0.66 to 0.93). Those who were continuously active had the lowest risk for HF (aHR, 0.77; 95% CI, 0.62 to 0.96). As compared with those who were inactive, those who exer-cised regularly, either performing vigorous or moderate PA, had a lower HF risk (aHR, 0.79; 95% CI, 0.69 to 0.91). Conclusion: Among individuals with newly diagnosed T2DM, the risk of HF was reduced in those with higher levels of PA after diagnosis was made. Our results suggest either increasing or maintaining the frequency of PA after the diagnosis of T2DM may lower the risk of HF.

The present study demonstrates a simple and robust strategy for fabricating nanocomposite thin films with high quality using a multi-component ZrCuSi single target. The ZrCuSi target was produced by using computer numerical control (CNC) based direct energy deposition (i.e., 3D printing). The influence of the energy density on morphological features and porosity of the ZrCuSi target surface was closely examined at a certain range of the energy density (75-225 J/mm3). X-ray diffractometer (XRD) and scanning electron microscopy (SEM) were applied for confirming the presence of the preferable crystallographic orientation and elucidating the morphological features of the nanocomposite target. In addition, functional nanocomposite thin films deposited from the ZrCuSi target presented in the current study were characterized. A scratch test and field-emission SEM (FE-SEM) revealed the adhesion properties and the morphological features of the nanocomposite coatings. Therefore, this work is highly expected to provide a facile and robust way to fabrication of e multi-component functional targets based ZrN, thereby envisioning usefulness of the nanocomposite coatings for automotive engine parts and various other wear protection applications.

Amorphous alloy thin films are promising materials for next-generation flexible electrode applications because of their large elastic strain limit, high strength, and high oxidation resistance. Here, we propose an Al-based amorphous thin film as a new transparent electrode material that exhibits excellent optical and electrical properties as well as bending durability. Furthermore, the good heat and corrosion resistivity of these Al-based amorphous thin films makes them extremely promising as next-generation flexible transparent electrodes used under various environment.

Numerical finite element method (FEM) calculation results reveal that the effective strain differs between the ductile Zr-based bulk metallic glass and brittle Hf-based bulk metallic glass (BMG) during rolling at room temperature. The current results demonstrated that the deformation mechanism of ductile Zr-based bulk metallic glass can be explained by perceptibility of multiple shear bands formation, however, the deformation mechanism of brittle Hf-based bulk metallic glass is represented by uniformly distribution of effective strain through overall specimen rather than localized into shear band. The variation of stress and the distribution of effective strain change significantly near the surface region of a Hf-based bulk metallic glass plate with increasing number of rolling passes. Under elasto-plastic deformation by cold rolling, the brittle Hf-based BMG has a thickness strain (εt) of −0.012, and the neutral effective strain (εeff) is 0.011 at the thickness direction, respectively. We present experimental confirmation that when the applied effective strain can be adjusted to below 1.1% during elasto-plastic deformation then even the brittle as-cast Hf-based BMG can be deformed up to 44% thickness reduction and 23% width expansion after multi-pass cold rolling without fracture by localization of shear stress.

Self-piercing riveting (SPR) is a high-speed fastening process that can join similar and dissimilar sheet materials without the need for pre-processing such as drilling or punching. During SPR processes, two overlapping sheets are joined by a rivet. The upper sheet is punched first by the rivet and then the lower sheet is deformed between the rivet and the die, creating a mechanical interlock. In this study, self-piercing riveting of aluminum alloy and carbon fiber reinforced polymer composites (CFRP) sheets was analysed using finite element simulations. For the finite element simulation of SPR processes, the orthogonal elasticity, the fracture model, and the cohesive zone model were used for describing the behaviour of CFRP. For validation of the composite material model, the punching process of CFRP was performed and the results were compared with FE predictions. The SPR process of the aluminum alloy and CFRP was simulated numerically and the performance of the joint was evaluated.

Property-targeted alloys were designed by exploring the phase stability and mechanical behaviors of a series of AlCoCrFeNi-based multicomponent alloy films fabricated via grain boundary diffusion-assisted solid-state alloying from their multilayer films. For phase identification and hardness evaluation for the multicomponent alloy films, compositional-dependent property contour maps were constructed, and their deformation behaviors were investigated. The results indicate that the alloys revealed a solid solution phase with an FCC structure, whereas Sigma phase was also formed in alloys with a high concentration of Cr. Moreover, the concentration ratio of Co To Ni was dominant to improve solid-solution strengthening, as expected by atomic-level complexity related to the electronegativity difference, and to activate metastable deformation behaviors by reducing the stacking fault energy. Based on the screening results of the compositional-dependent behaviors in the films, consequently, we developed novel metastable CoCrFeNi-based high-entropy alloys with the outstanding tensile properties of 234 MPa in yield strength, 720 MPa in ultimate tensile strength, and 80 % in fracture strain through compositional tailoring the concentration ratio of Co to Ni. This approach shows prospects of property customization of multicomponent alloys

Zr-based metallic glasses are prepared by quenching supercooled liquid under pressure. These glasses are stable in ambient conditions after decompression. The High Pressure Quenched glasses have a distinct structure and properties. The pair distribution function shows redistribution of the Zr-Zr interatomic distances and their shift towards smaller values. These glasses exhibit higher density, hardness, elastic modulus, and yield stress. Upon heating at ambient pressure, they show volume expansion and distinct relaxation behavior, reaching an equilibrated state above the glass transition. These experimental results are consistent with an idea of pressure-induced low to high density liquid transition in the supercooled melt.

In the present work, a novel Cu46Zr40Ti8.5Al5.5 metallic glass is synthesized by melt spun technique and investigated for corrosion behavior at various molar concentrations in acidic, neutral and alkaline solutions (at different pH levels), using potentiodynamic polarization experiment and electrochemical impedance spectroscopy (EIS). Surface morphology and composition analysis after corrosion test were carried out by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Results indicate that corrosion resistance decreases with increase in chloride ion concentration in case of acidic and neutral media. However, in case of alkaline solution, corrosion resistance is found to be similar for pH 8 and pH 10, but is observed to decrease at pH 12. Melt spun sample was highly susceptible to pitting corrosion at higher molarity in acidic and neutral solution as observed from SEM analysis. EDS results indicate depletion of galvanically active metals (Al > Ti > Zr) from pit interior. Furthermore, an attempt has been made to study the influence of Al in corrosion behavior of the sample.