High-entropy composites (HECs) were subjected to severe straining by high-pressure torsion (HPT) to evaluate their influence on the evolution of microstructure and deformation behavior. Severe straining leads to a homogeneously strained microstructure and inhomogeneous micro-shear bands in these HECs. Nb addition in HECs varies the microstructure from single phase to eutectic, and the Vickers microhardness in HPT HECs increases to 7.45 GPa. Nb addition up to x = 0.80 in as-cast HECs improves the strength of these materials at the expense of its plasticity. Nevertheless, severe straining provides a better combination of strength and ductility without sacrificing its plasticity. Such improvement in properties is attributed to the evolved microstructural features, formation of “transformation-shear bands (T-SBs)” and “deformation-shear bands (D-SBs)” at severe straining. This assures the homogeneous deformation by shear banding and suggests that shear banding is the dominant deformation mechanism when the lamellar spacing becomes saturated upon severe straining.

Positron annihilation spectroscopy and differential scanning calorimetry were used to evaluate the changes of the atomic configurations in Zr-based metallic glasses (MGs) due to alloying and plastic deformation. The correlation between the atomic configurations of MGs and the amorphous-to-icosahedral phase transition due to heating was investigated. The results indicate that the free volume frozen in the as-cast Zr60Al15Ni25, Zr65Al7.5Ni10Cu17.5, and Zr65Al7.5Ni10Cu17.5Ag5 MGs substantially decreases in sequence. More excess free volume is introduced in Zr65Al7.5Ni10Cu17.5Ag5 MG due to cold rolling and milling. The annihilation of free volume due to alloying considerably stabilizes the icosahedral structure of MGs, which enhances the nucleation and growth of quasicrystals upon heating. However, the nucleation and growth of quasicrystals are considerably suppressed in Zr65Al7.5Ni10Cu17.5Ag5 MG due to cold rolling and milling, during which the more introduced excess free volume results in substantial destruction of short-range order with 5-fold symmetry. The present work further provides direct evidence for the prevalence of icosahedral short-range order in MGs.

The addition of Co to CuZr-based shape memory bulk metallic glass composites stabilizes the high temperature B2-CuZr and decreases its stacking faulty energy, which promotes an increase in ductility caused by an easier twinning formation. A similar effect is expected for TiCu-based alloys. The present work aims to investigate the effect of Co additions on the phase formation, mechanical properties, and thermal stability of rapidly solidified Ti–Cu-based alloys. Rods of six Ti–Cu-based compositions with different amounts of Co were prepared by Cu-mold suction casting and investigated by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, dilatometry, and compression tests. The results show that the addition of Co decreases the glass-forming ability of Ti–Cu-based alloys and stabilizes B2 Ti(Cu,Ni,Co) at room temperature. The Co-added alloys exhibit an almost identical phase formation and microstructure, but their mechanical behavior is completely different nonetheless, which is mainly connected with the different composition of the B2 phase. The addition of Co makes the stress-induced martensitic transformation of this phase more difficult, which is one of the main reasons for the increase of the yield strength when a higher amount of Co is added.

The shear-band propagation in bulk metallic glasses (BMGs) during deformation plays a key role in determining their macroscopic ductility. In this work, the shear band propagation during plastic deformation was investigated in the Cu46Zr46Al8 BMG and its in situ or ex situ prepared BMG composites. Compared with the brittle BMG, both types of ductile BMG composites show a more stable shear banding behavior as revealed by a larger power-law scaling exponent obtained from statistical analysis of serrations recorded in compressive curves. A higher cut-off elastic energy density (δc) linked with the multiplication of shear bands is observed for the in situ prepared BMG composites. However, the ex situ fabricated BMG composites show an almost equivalent or slightly larger δc since the dominant shear band but not multiple shear bands mainly governs their deformation. Such observations imply that the shear banding stability of BMGs during deformation is enhanced not only by inducing multiple shear bands but also by obstructing the movement of the dominant shear band at its driven path.

The Al–50Si alloy, as a kind of potential electronic packaging material, is manufactured by different methods, such as casting and spray deposition. The possible influences of the P refiner on the microstructure of the Al–50Si alloy are investigated at different cooling rates. The refinement mechanism of primary Si phase is discussed in view of the P refiner addition, and the variation of the cooling rates. The thermal conductivity (TC), as a key parameter for electronic materials, is measured. The coupled effects of the cooling rate and the addition of the P refiner during the solidification of the Al–50Si alloy on the TC are elucidated based on structural observations. Furthermore, the porosity in the Al–50Si alloy is treated as a second phase influencing the TC.

The glass-forming Ti75Zr10Si15 and Ti60Zr10Nb15Si15 alloys composed of nontoxic elements may represent new materials for biomedical applications. For this study, melt-spun alloy samples exhibiting glass–matrix nanocomposite structures were subjected to thermal oxidation treatments in synthetic air to improve their surface characteristics. 550 °C was identified as the most appropriate temperature to carry out oxidative surface modifications while preserving the initial metastable microstructure. The modified surfaces were evaluated considering morphological and structural aspects, and it was found that the oxide films formed at 550 °C are amorphous and consist mainly of TiO2; their thicknesses were estimated to be ∼560 nm for Ti75Zr10Si15 and ∼460 nm for Ti60Zr10Nb15Si15. The thermally treated sample surfaces exhibit not only higher roughnesses and higher hardnesses but also improved wettability compared to the as-spun materials. By immersion of oxidized samples in simulated body fluid Ca- and P-containing coatings exhibiting typical morphologies of apatite are formed.

Al–12Si (80 vol%)–Ti52.4Al42.2Nb4.4Mo0.9B0.06 (at.%) (TNM) composites were successfully produced by the selective laser melting (SLM). Detailed structural and microstructural analysis shows the formation of the Al6MoTi intermetallic phase due to the reaction of the TNM reinforcement with the Al–12Si matrix during SLM. Compression tests reveal that the composites exhibit significantly improved properties (∼140 and ∼160 MPa higher yield and ultimate compressive strengths, respectively) compared with the Al–12Si matrix. However, the samples break at ∼6% total strain under compression, thus showing a reduced plasticity of the composites. Sliding wear tests were carried out for both the Al–12Si matrix and the Al–12Si–TNM composites. The composites perform better under sliding wear conditions and the wear rate increases with increasing loads. At high loads, the wear takes place at three different rates and the wear rate decreases with increasing experiment duration.

Cast-iron (CI) based bulk amorphous alloy with compositions of Fe75.5−xC6.0Si3.3B5.5P8.7Cu1.0Alx (x = 0, 1 at.%) was synthesized by Cu mold casting. As indicated by increased critical diameters (dmax) for the amorphization, the substitution of Al enhanced the glass-forming ability of the alloy. However, the onset temperature of crystallization (Tx) and the range of supercooled liquid region (ΔTx) of the alloy decreased upon Al addition from 500 °C and 28 °C to 475 °C and 25 °C, respectively. It was revealed that the decreased thermal stability of the amorphous phase is related to the enhanced crystallization tendency to form primary α-Fe phase. Upon the nanocrystallization of primary α-Fe phase the Al-added alloy shows enlarged Ms of 176 emu g−1, still keeping a reasonable small Hc value of 0.086 Oe. The present study revealed that the minor Al addition enhances not only the glass-forming ability, but also the nanocrystallization behavior of the CI based bulk amorphous alloy.

Five well-known Zr-based alloys of the systems Zr–Cu–Al–(Ni–Nb, Ni–Ti, Ag) (Cu = 15.4–36 at.%) with the highest glass-forming ability were comparatively analyzed regarding their pitting corrosion resistance and repassivation ability in a chloride-containing solution. Potentiodynamic polarization measurements were conducted in the neutral 0.01 M Na2SO4 + 0.1 M NaCl electrolyte and local corrosion damages were subsequently investigated with high resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive x-ray spectroscopy (EDX). Both pitting and repassivation potential correlate with the Cu concentration, i.e., those potentials decrease with increasing Cu content. Pit morphology is not composition dependent: while initially hemispherical pits then develop an irregular shape and a porous rim. Corrosion products are rich in Cu, O, and often Cl species. A combination of low Cu and high Nb or Ti contents is most beneficial for a high pitting resistance of Zr-based bulk metallic glasses. The bulk glassy Zr57Cu15.4Al10Ni12.6Nb5 (Vit 106) and Zr52.5Cu17.9Al10Ni14.6Ti5 (Vit 105) alloys exhibit the highest pitting resistance.

The magnetic Fe–6.5 wt% Si powder was produced by gas atomization and its microstructure was also investigated. The secondary dendritic arm spacing (SDAS) is related to the droplet size, ${\rm{\lambda }} = 0.29 \cdot {D^{0.5}}$, and the numerical solidification model was applied to the system, giving rise to the correlation of microstructure to the solidification process of the droplet. It is found that the solid fraction at the end of recalescence is strongly dependent on the undercooling achieved before nucleation; the chances for the smaller droplets to form the grain-refined microstructures are less than the larger ones. Furthermore, the SDAS is strongly influenced by the cooling rate of post-recalescence solidification, and the relationship can be expressed as follows, ${\rm{\lambda }} = 74.2 \cdot {\left( {\dot T} \right)^{ - 0.347}}$. Then, the growth of the SDAS is driven by the solute diffusion of the interdendritic liquids, leading to a coarsening phenomenon, shown in a cubic root law of local solidification time, ${\rm{\lambda }} = 10.73 \cdot {\left( {{t_f}} \right)^{0.296}}$.

Confining light metal hydrides in micro- or mesoporous scaffolds is considered to be a promising way to overcome the existing challenges for these materials, e.g. their application in hydrogen storage. Different techniques exist which allow us to homogeneously fill pores of a host matrix with the respective hydride, thus yielding well defined composite materials. For this report, the ordered mesoporous carbon CMK-3 was taken as a support for LiAlH4 realized by a solution impregnation method to improve the hydrogen desorption behavior of LiAlH4 by nanoconfinement effects. It is shown that upon heating, LiAlH4 is unusually oxidized by coordinated tetrahydrofuran solvent molecules. The important result of the herein described work is the finding of a final composite containing nanoscale aluminum oxide inside the pores of the CMK-3 carbon host instead of a metal or alloy. This newly observed unusual oxidation behavior has major implications when applying these compounds for the targeted synthesis of homogeneous metal–carbon composite materials.

Among the different porous materials, bulk metallic glass (BMG) foams are of special interest due to their high strength combined with large elastic limit. Large surface areas and, therefore, high reactivity in chemical applications can be achieved by properly adjusting the pore characteristics. Pore size and pore size distribution are the key factors for determining the overall performance of open-cell porous materials used for functional applications, such as filtration or catalysis. As a result, the control of these factors is a necessary requirement for material design and application. In this work, BMG foams are produced by powder metallurgy through the selective dissolution of a fugitive phase. The work is focused on the manufacturing processes needed to properly control pore size and pore size distribution. The results reveal that customized hybrid BMG porous structures can be produced through the controlled milling of the BMG-composite powders.

In this work, composites consisting of the Al 2024 matrix reinforced with β-Al3Mg2 particles have been produced by powder metallurgy with the aim of increasing the strength of the matrix and, at the same time, reducing the density of the material. The β-Al3Mg2 phase represents an ideal candidate as reinforcement in lightweight composites due to its low density and high-temperature strength. The β-Al3Mg2 reinforcement remarkably improves the mechanical properties of the 2024 matrix. In particular, the composite with 20 vol.% reinforcement display yield and compressive strengths exceeding that of the unreinforced matrix by about 120 and 180 MPa, while retaining appreciable plastic deformation of about 30 %. The strength of the material is further increased for the samples with 30 and 40 vol.% of β-Al3Mg2 phase, however, the composites show reduced plastic deformation of 11 and 4.5 %. Furthermore, the addition of the low-density β-Al3Mg2 particles decreases the density of the materials below that of the unreinforced 2024 matrix, considerably increasing the specific strength of the composites.

A new technique for micropatterning Fe-based bulk metallic glass surfaces is reported. The transpassive dissolution process is utilized for a defined localized material removal when using a pulsed electrochemical micromachining process. By applying submicrosecond pulses between a work piece and a tool electrode, microholes of high aspect ratio and depth of up to 100 μm can be machined into the bulk glassy Fe65.5Cr4Mo4Ga4P12C5B5.5 alloy. Two potential electrolytes are identified for the machining process. For these electrolytes, different reaction mechanisms are discussed. The possibility of machining more complex structures is demonstrated for the most promising electrolyte, a methanolic H2SO4solution. The impact of the process parameters, pulse length and pulse voltage, on the machining gap and the surface quality of the machined structures is evaluated.

The oxidation behavior of Cu50Zr50 and Cu46Zr46Al8 glasses during continuous heating up to 1073 K has been investigated, with special emphasis on the oxidation resistance in the supercooled liquid (SCL) state. For Cu50Zr50, the oxide layer mostly consists of monoclinic ZrO2 (m-ZrO2), while for Cu46Zr46Al8, the oxide layer consists of two different layers: an outer layer consisting of tetragonal ZrO2 (t-ZrO2) + Al2O3 + metallic Cu (oxidation product from the SCL state of the glass matrix) and inner layer comprised of m-ZrO2 + metallic Cu islands (oxidation product from the crystallized matrix). Cu-enriched regions consisting of Cu51Zr14 (in Cu50Zr50) or AlCu2Zr + Cu70Zr15Al15 + Cu51Zr14 (in Cu46Zr46Al8) are present below the oxide layer. The present study shows that the addition of Al (8 at.%) in Cu50Zr50 results in a significant deterioration of the oxidation resistance in the SCL state since the solutionizing of Al in t-ZrO2 leads to a higher oxygen ion vacancy concentration, thus providing a higher activity of oxygen ions.

Improved room temperature plasticity was achieved by microalloying Cu in a series of (Fe71Nb6B23)100−xCux (x = 0, 0.25, 0.5, 0.75, and 1) glass matrix alloys with tunable size and volume fraction of precipitates composed of α-Fe and Fe23B6 phases. When ∼10-nm-sized nano-scale precipitates are formed with a size comparable to the shear bandwidth by controlling the added content of Cu, the (Fe71Nb6B23)99.5Cu0.5 alloy exhibits a maximum plastic strain of 4.3 ± 0.8% with pronounced multiple shear banding. A further increase in the size of the precipitates up to micrometer scale results in catastrophic fracture accompanied with irregular cracks, revealing that the fracture mechanism of the different alloys is controlled by the precipitate size.