Fabrication of metastable crystalline nanocomposites by flash annealing of Cu47.5Zr47.5Al5 metallic glass using joule heating

Flash Joule-heating was applied to the Cu47.5Zr47.5Al5 metallic glass for designing fully crystalline metastable nanocomposites consisting of the metastable B2 CuZr and low-temperature equilibrium Cu10Zr7 phases. The onset of crystallization was in situ controlled by monitoring resistivity changes in the samples. The effect of heating rate and annealing time on the volume fraction of the crystalline phases and mechanical properties of the nanocomposites was studied in detail. Particularly, an increase of the heating rate and a decrease of the annealing time lead to a lower number of equilibrium Cu10Zr7 precipitates and an increase of tensile ductility. Tailoring of these non-equilibrium microstructures and mechanical properties may not be possible unless one starts with a fully glassy material that opens new perspectives for designing metastable nanomaterials with unique physical properties. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.EC 111/26-1, MA 3333/13-105K2012European Research Council, ERC: ERC-2013-ADG-340025Funding: This research was funded by the German Federal Ministry of Education and Science BMBF, grant number 05K2012, the German Science Foundation under the Leibniz Program, grant numbers EC 111/26-1 and MA 3333/13-1, and the European Research Council (ERC) under the ERC Advanced Grant INTELHYB, grant number ERC-2013-ADG-340025

Fabrication of metastable crystalline nanocomposites by flash annealing of Cu47.5Zr47.5Al5 metallic glass using joule heating

Flash Joule-heating was applied to the Cu47.5Zr47.5Al5 metallic glass for designing fully crystalline metastable nanocomposites consisting of the metastable B2 CuZr and low-temperature equilibrium Cu10Zr7 phases. The onset of crystallization was in situ controlled by monitoring resistivity changes in the samples. The effect of heating rate and annealing time on the volume fraction of the crystalline phases and mechanical properties of the nanocomposites was studied in detail. Particularly, an increase of the heating rate and a decrease of the annealing time lead to a lower number of equilibrium Cu10Zr7 precipitates and an increase of tensile ductility. Tailoring of these non-equilibrium microstructures and mechanical properties may not be possible unless one starts with a fully glassy material that opens new perspectives for designing metastable nanomaterials with unique physical properties

New-generation biocompatible Ti-based metallic glass ribbons for flexible implants

We introduce five new biocompatible Ti-based metallic glass (MG) compositions with different metalloid and soft metal content for a synergistic improvement in corrosion properties. Without any potentially harmful elements such as Cu, Ni or Be, these novel alloys can eliminate the risk of inflammatory reaction when utilized for permanent medical implants. Excluding Cu, Ni or Be, which are essential for Ti-based bulk MG production, on the other hand, confines the glass-forming ability of novel alloys to a moderate level. In this study, toxic-element free MG alloys with significant metalloid (Si–Ge–B, 15–18 at.%) and minor soft element (Sn, 2–5 at.%) additions are produced in ribbon form using conventional single-roller melt spinning technique. Their glass-forming abilities and their structural and thermal properties are comparatively investigated using X-ray diffraction (XRD), synchrotron XRD and differential scanning calorimetry. Their corrosion resistance is ascertained in a biological solution to analyze their biocorrosion properties and compare them with other Ti-based bulk MGs along with energy dispersive X-ray. Ti60Zr20Si8Ge7B3Sn2 and Ti50Zr30Si8Ge7B3Sn2 MG ribbons present a higher pitting potential and passivation domain compared with other Ti-based MG alloys tested in similar conditions. Human mesenchymal stem cell metabolic activity and cytocompatibility tests confirm their outstanding cytocompatibility, outperforming Ti-Al6-V4

X-ray Diffraction Study of iPP/clay and iPP/TiO2 Composites Relating to Micromechanical Properties

Composites of isotactic polypropylene with various contents of white clay or titanium dioxide TiO2 were prepared by extrusion molding. The extruded composites were melt-pressed at two different temperatures, and,thereafter, either slowly cooled, or quenched to room temperatures. It is shown that the structure of all the samples, as revealed by wide-angle X-ray scattering and small-angle X-ray scattering (SAXS), depends on the processing conditions. The lack of SAXS maxima in the composites suggests that the presence of the microadditives hinders the stacking of iPP lamellae. Furthermore, the microindentation hardness H in the slowly cooled composites is influenced by the type and amount of the filler used. However, in the quenched samples H depends only on the amount of the filler used, and not on its type. In case of the quenched iPP/clay composites, the relationship between H and the Young’s modulus E is found to be H/E approx. equal to 0.12, in good agreement with Struik’s theoretical predictions of sigma e approx. equal to E/30, in consonance with results previously obtained for a series of polyethylene samples with different morphology.Peer reviewe

Crystalline plasticity in isotactic polypropylene below and above the glass transition temperature

In-situ X-ray diffraction was applied to isotactic polypropylene with a high volume fraction of α-phase (α-iPP) while it has been compressed at temperatures below and above its glass transition temperature Tg. The diffraction patterns were evaluated by the Multi-reflection X-ray Profile Analysis (MXPA) method, revealing microstructural parameters such as the density of dislocations and the size of coherently scattering domains (CSD-size). A significant difference in the development of the dislocation density was found compared to compression at temperatures above Tg, pointing at a different plastic deformation mechanism at these temperatures. Based on the individual evolutions of the dislocation density and CSD-size observed as a function of compressive strain, suggestions for the deformation mechanisms occurring below and above Tg are made

Milch und Käse

n/