The structural evolution in the undercooled liquid plays an essential role in comprehending the crystal-lization mechanism, which is of benefit to understand the glass-forming ability (GFA), the thermal stability, and the development of glassy alloy (GA) with excellent properties. In this work, Zr61Ti2Cu25Al12 GAs with different undercooled states were obtained by means of electromagnetic levitation. The Zr61Ti2Cu25Al12 GA can achieve an undercooling degree of 226 K, which is larger than previously reported GAs. Calorimetric analysis indicates a more relaxed state occurs in the GA cooled from the larger undercooling. Hardness tests show that deep undercooling can lead to a significant increase in hardness compared to a low undercooling level. It might be attributed to a liquid-liquid transition, bringing out an obvious change in the atomic volume of the glassy phase. In addition, a pronounced ordered structure apparently exists when the system reaches the larger undercooling degree. Our findings provide a new perspective for the study of the un-dercooled liquid, and the solidification kinetics of GAs.(c) 2023 Elsevier B.V. All rights reserved.

Controlling shear band propagation is the key to obtain ductile metallic glasses. Here, we use a residual stress field to vary the direction of shear band propagation. We ascribe this behavior to the effect of the stress field on the activation of shear transformation zones (STZs) along their characteristic direction and we quantify this contribution to the energy of the process. Because of the progressively adverse orientation of the stress field, the energy stored as shear in the STZ decreases to a level where shear band propagation at alternative angles becomes energetically more favorable.

Shape Memory and Superelasticity is pleased to announce that ‘‘Properties of Cu-Based Shape-Memory Alloys Prepared by Selective Laser Melting’’ (Volume 3, Issue 1, March 2017) is the winner of the 2017 Best Paper Award. The winning authors are Mr. Tobias Gustmann, Dr. Uta Kühn, and Dr. Simon Pauly, IFW Dresden, Institute for Complex Materials, Dresden, Germany; Mr. Jonadabe M. dos Santos and Prof. Piter Gargarella, Departamento de Engenharia de Materiais (DEMa), Universidade Federal de São Carlos (UFSCar), São Carlos, Brazil; and Prof. Jan Van Humbeeck, Department of Materials Engineering, KU Leuven, Leuven, Belgium. The paper was chosen by the journal’s associate editors. The award will be presented to the winning authors at the 2019 International Conference on Shape Memory and Superelastic Technologies (SMST), May 13–17, 2019, at The Bodenseeforum in Konstanz, Germany. The Shape Memory and Superelasticity Best Paper Award, in addition to the recognition, includes a plaque and $1000 worth of ASM International products and services. The Associate Editors of the journal believe it is important to evaluate the quality contributions published in Shape Memory and Superelasticity and to provide recognition of excellent work and its publication. Each paper is Tobias Gustmann

This paper presents results about the influence of the selective laser melting (SLM) process parameters on a FeCr4Mo1V1W8C1 (wt%) alloy regarding microstructure and mechanical behavior. Tailored parameter variation studies were performed to obtain crack-free and highly dense SLM parts. The microstructure was studied using scanning electron microscopy, X-ray diffraction, Auger electron spectroscopy, and scanning transmission electron microscopy. Additionally, the mechanical properties were investigated by compression and tensile tests. The obtained microstructure is composed of complex nanoscale carbides, retained austenite, and martensite. Caused by the fast directional cooling during SLM, a completely dendritic solidification aligned in building direction occurs. Non-equilibrium segregation leads to an orderly phase arrangement of complex carbides at the boundary of the dendrites surrounded by retained austenite and martensite in the center of the dendrites. A strong work hardening behavior was observed, based on an austenite-to-martensite phase transformation (TRIP effect). This effect accounts for the outstanding mechanical properties such as compression strength of 6000 MPa, a 0.2% tensile yield strength of 560 MPa, and an ultimate tensile strength of over 1000 MPa. These findings reveal that SLM is advantageous for the processing of ultra-high-strength FeCrMoVWC tool steel.

This study examined into the surface roughness and microhardness of titanium (Ti6Al4V) alloy caused by the abrasive waterjet milling (AWJM) process. Waterjet pressure (WJP), stand-off distance (SOD), and abrasive flow rate (AFR) were studied on surface roughness and microhardness in three distinct regions: the initial damage region (IDR), the smooth cutting region (SCR) and the rough cutting region (RCR). X-Ray Diffraction was used to examine the lattice strain, crystallite size, and phase composition of abrasive waterjet machined samples. WJP is discovered to be a useful factor in reducing surface roughness, increasing striations, and decreasing waviness on the AWJM's surface. The higher hardness is caused by the material's permanent plastic deformation during the AWJM process. The FWHM of AWJ machined samples is reduced, and the presence of TiOxCx increases the crystallite size during the AWJM process. In relation to surface deformation, the AWJM causes severe plastic deformation (SPD), resulting in continuous internal oxide formation.

Additive Fertigungstechnologien, wie das Selektive Laserschmelzen (SLM), haben zahlreiche Vorteile gegenüber konventionellen Fertigungsverfahren, wie nahezu uneingeschränkte geometrische Gestaltungsfreiheit, Funktionsintegration und hohe Materialausnutzung. Daher gewinnt die Technologie in der Bauteilfertigung zunehmend an Interesse, um z. B. maßgeschneiderte Werkzeuge für spezifische Anwendungsbereiche, hoch belastbare Leichtbaustrukturen für die Automobil- oder Luftfahrtindustrie oder Individualteile in der Medizintechnik zu fertigen. Um den stetig wachsenden Beanspruchungen der Bauteile gerecht zu werden, benötigt man maßgeschneiderte Werkstoffe, die für die additive Fertigung geeignet sind.

Two shape-memory alloys with the nominal compositions (in wt.%) Cu–11.85Al–3.2Ni–3Mn and Cu–11.35Al–3.2Ni–3Mn–0.5Zr were prepared by selective laser melting (SLM). The parameters were optimised to identify the process window, in which almost fully dense samples can be obtained. Their microstructures were analysed and correlated with the shape-memory behaviour as well as the mechanical properties. Suction-cast specimens were also produced for comparison. Mainly, β 1 ′ martensite forms in all samples, but 0.5 wt.% of Zr stabilises the Y phase (Cu 2 AlZr), and its morphology depends on the thermal history and cooling rate. After annealing, the Y phase is primarily found at the grain boundaries hampering grain coarsening. Due to the relative high cooling rates applied here, Zr is mostly dissolved in the martensite in the as-prepared samples and it has a grain-refining effect only up to a critical cooling rate. The Zr-containing samples have increased transformation temperatures, and the Y phase seems to be responsible for the jerky martensite-to-austenite transformation. All the samples are relatively ductile because they mostly fracture in a transgranular manner, exhibiting the typical double yielding. Selective laser melting allows the adjustment of the transformation temperatures and the mechanical properties already during processing without the need of a subsequent heat treatment.

Boron refinement is an established method to refine the grain structure of titanium alloys. The effect of boron on microstructure of multicomponent Ti–Nb–Cu–Co–Al–B alloys was studied. These as-cast alloys exhibit a composite-like microstructure consisting of about 92vol% of β-Ti dendrites surrounded by an ultrafine-structured eutectic composed of β-Ti and B2 TiCo. It was found that significant additions (up to 1at%) of boron do not result in a pronounced refinement of microstructure in these alloys. However, noticeable strengthening and stiffening effects are observed for the alloys with increasing boron concentration. In particular, the yield strength of Ti–13.6Nb–6Co–5.1Cu–6.5Al (at%) improves from 1110±30MPa to 1200±30MPa with addition of 1at% of boron. Additionally, increasing boron content affects the morphology of the eutectic structure causing its degradation.

The effect of annealing on the tribological and corrosion properties of Al–12Si samples produced by selective laser melting (SLM) is evaluated via sliding and fretting wear tests and weight loss experiments and compared to the corresponding material processed by conventional casting. Sliding wear shows that the as-prepared SLM material has the least wear rate compared to the cast and heat-treated SLM samples with abrasive wear as the major wear mechanism along with oxidation. Similar trend has also been observed for the fretting wear experiments, where the as-prepared SLM sample displays the minimum wear loss. On the other hand, the acidic corrosion behavior of the as-prepared SLM material as well as of the cast samples is similar and the corrosion rate is accelerated by increasing the heat treatment temperature. This behavior is due to the microstructural changes induced by the heat treatment, where the continuous network of Si characterizing the as-prepared SLM sample transforms to isolated Si particles in the heat-treated SLM specimens. This shows that both the wear and corrosion behaviors are strongly associated with the change in microstructure of the SLM samples due to the heat-treatment process, where the size of the hard Si particles increases, and their density decreases with increasing annealing temperature.

•Nanoindentation studies are carried out to capture shear banding initiation.•A wedge indentation experiment is developed to observe shear band evolution.•A finite element model is developed to characterise the location of shear bands.

The effect of pre-existing shear bands induced by cold-rolling on the crystallization behavior was investigated in the Cu46Zr46Al8 bulk metallic glass. It was found that with increasing degree of pre-deformation, more shear bands are created resulting in the decrease of the crystallization activation energy for the alloy. Our experimental results demonstrate that pre-existing shear bands can promote the nucleation of crystals, which is discussed in terms of nucleation thermodynamics and kinetics aspects.

This study describes the correlation between microstructure and mechanical properties of an ultra-high-strength Fe 86.7 Cr 4.4 Mo 0.6 V 1.1 W 2.5 C 4.7 (at.%) alloy manufactured under high cooling rates and pure conditions. The applied preparation conditions promote the formation of non-equilibrium phases such as martensite, retained austenite and special carbides already in the as-cast state. The carbides form a 3-dimensional skeleton-like structure between the retained austenite and the martensite. This hard and finely ramified carbide network distributed throughout the entire ingot is a specific characteristic of this alloy and important for its excellent mechanical properties. The material exhibits extremely high engineering compression strength of almost 5500 MPa combined with a large compression strain of about 23% due to deformation-induced martensite formation. Furthermore, the alloy possesses a high hardness and tensile strength in the as-cast condition. This combination of mechanical properties leads to an outstanding engineering material for a variety of structural applications in the automotive and tool manufacturing industry.

Multi-methodological approaches combining quantum-mechanical and/or atomistic simulations with continuum methods have become increasingly important when addressing multi-scale phenomena in computational materials science. A crucial aspect when applying these strategies is to carefully check, and if possible to control, a variety of intrinsic errors and their propagation through a particular multi-methodological scheme. The first part of our paper critically reviews a few selected sources of errors frequently occurring in quantum-mechanical approaches to materials science and their multi-scale propagation when describing properties of multi-component and multi-phase polycrystalline metallic alloys. Our analysis is illustrated in particular on the determination of i) thermodynamic materials properties at finite temperatures and ii) integral elastic responses. The second part addresses methodological challenges emerging at interfaces between electronic structure and/or atomistic modeling on the one side and selected continuum methods, such as crystal elasticity and crystal plasticity finite element method (CEFEM and CPFEM), new fast Fourier transforms (FFT) approach, and phase-field modeling, on the other side.

Bulk metallic glasses (BMGs) generally fail in a brittle manner under uniaxial, quasistatic loading at room temperature. The lack of plastic strain is a consequence of shear softening, a phenomenon that originates from shear-induced dilation that causes plastic strain to be highly localized in shear bands. So far, significant tensile ductility has been reported only for microscopic samples of around 100 nm (ref. 4) as well as for high strain rates, and so far no mechanisms are known, which could lead to work hardening and ductility in quasistatic tension in macroscopic BMG samples. In the present work we developed CuZr-based BMGs, which polymorphically precipitate nanocrystals during tensile deformation and subsequently these nanocrystals undergo twinning. The formation of such structural heterogeneities hampers shear band generation and results in macroscopically detectable plastic strain and work hardening. The precipitation of nanocrystals and their subsequent twinning can be understood in terms of a deformation-induced softening of the instantaneous shear modulus. This unique deformation mechanism is believed to be not just limited to CuZr-based BMGs but also to promote ductility in other BMGs.

Two crystalline Fe-Cr-Mo-Ga-Si alloys were prepared by copper mold casting using various types of crucible materials. The materials were derived from a bulk metallic glass-forming composition with the aim to enhance the ductility of this high-strength alloy. The rods obtained under different conditions show significantly varying microstructures and mechanical properties. The best mechanical characteristics were found for samples, which essentially consist of ductile Ga-rich dendrites dispersed in high-strength Cr- and Mo-rich interdendritic phase(s). The combination of the soft and hard phases results in a composite material with high fracture strength (about 3 GPa) connected with very good plasticity (up to 13%). The discovery of new high-strength Fe-based materials with a good deformability is an important step ahead for the further development of Fe-based alloys as engineering materials.

Bismuth telluride samples are compared with respect to the evolution of their thermoelectric material parameters like thermal and electrical conductivity. The Seebeck coefficient is discussed in dependence on the melt spinning fabrication technique. The melt spinner used is only able to produce small thin ribbon shaped specimens, some as thin as 10 mu m. This limits melt spinning to mainly production of research specimens for alloys with high critical cooling rate, which are difficult to fabricate with other techniques. Additional parameters are alloying or doping of the base material by comparing the properties as prepared to different annealing conditions. The intrinsic p- and n-doped material was alloyed with up to 0.5% lead telluride by rapidly cooling the bulk material to improve the thermoelectric properties analysed from RT up to about 600 K. A Seebeck coefficient of well above 200 mu V/K could be obtained for p- and n-type materials. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zr-based bulk metallic glasses (BMG) like, Zr59Ti3Cu20Al10Ni8, Zr58.5Nb2.8Cu15.6 Al10.3Ni12.8, Zr57Nb5Cu15.4Al10Ni12.6, Zr60Ti4 Nb4Cu14Al9Ni9, Zr64Ti5Nb3Cu14.7Al7.4Ni5.9, Zr60Ti2Nb6Cu14Al9Ni9 and Zr60Pd5Cu15Al10Ni10 were investigated for corrosion behaviour in acid solutions of 1 N H2SO4 and 1 N HNO3, and acidic chloride solutions of 1 N H2SO4 containing 0.02, 0.2 and 0.5 M NaCl, in order to understand their passivation characteristics and pitting corrosion resistance, respectively. The results of the present investigation revealed (i) corrosion resistance of Zr-based bulk metallic glasses is good in both H2SO4 and HNO3 acidic medium, (ii) pitting corrosion resistance depends on the composition and structure of the alloys investigated; in general, addition of Ti and Nb enhanced the pitting corrosion resistance, (iii) amorphous and quasicrystalline structures exhibit better corrosion resistance than crystalline structure in both acidic and acidic chloride media, and (iv) copper-enriched layer below the ZrO2 passive film deteriorate the pitting resistance by dissolution to cupric ions and forming cupric chloride interacting with chloride ions. The study recommends reduction or replacement of copper with alternate alloying elements in order to enhance the corrosion resistance of BMG for structural applications.

High-strength Ti–Nb–Cu–Ni–Al in situ cast composites were prepared via arc-melting and injection casting into a copper mold. The microstructure of the Ti-based alloys consists of a bcc β-Ti type main phase and minor amounts of several nanocrystalline interdendritic phases. The optimization of the Ti-based alloy composition is performed to achieve both high strength and high ductility. The best combination of strength and ductility was found for a copper mold cast (TiNb)79(CuNiAl)21 alloy, which exhibits a fracture strength of more than 2000 MPa coupled with a plastic strain of 30%. Also the arc-melted ingot of this alloy exhibits similar mechanical properties compared to its mold cast counterpart. These features significantly improve the mechanical behavior of such composites and open the possibility of obtaining tailored mechanical properties by controlling composition and solidification conditions.