Compositional and Structural Evolution during Ball Milling of Ti-based Metallic Glass Powder

Densification mechanism of Ti-based metallic glass powders during spark plasma sintering process

In the present study, Cu60Zr30Ti10 metallic glass powders were prepared by mechanical alloying of pure Cu, Zr, and Ti powder mixtures. Cu60Zr30Ti10 metallic glass composite powders were obtained after 5 h of milling as confirmed by X-ray diffraction and transmission electron microscopy. The metallic glass powders were found to exhibit a supercooled liquid region before crystallization. Cu60Zr30Ti10 bulk metallic glass were synthesized by vacuum hot pressing the as-milled Cu60Zr30Ti10 metallic glass powders at 723 K in the pressure range of 0.72 ~ 1.20 GPa. Cu60Zr30Ti10 BMG with nanocrystalline precipitates homogeneously embedded in a highly dense glassy matrix was successfully prepared under applied pressures. It was found that the pressure could enhance the thermal stability and prolong the existence of amorphous phase inside Cu60Zr30Ti10 powders.

Milling amorphous FeSiB ribbons with vibratory ball and disc mills

Mechanical attrition—the mechanical alloying or milling of powders—is a very versatile and potent method of obtaining nanocrystalline or ultrafine grain structures with enhanced properties. This article presents three examples of enhanced properties obtained by materials in which the grain size has been reduced to the nanoscale or ultrafine scale by ball milling and consolidation of powders. Very high strength/hardness—the highest hardness yet reported for crystalline Mg alloys—for a ball milled Mg97Y2Zn1 alloy is due in part to the nanocrystalline grain structure, along with nanoscale precipitates. A ternary Cu-base alloy with a low stacking fault energy was found to have both high strength and good ductility in a nanocrystalline material synthesized by the in situ ball milling consolidation method. This is another example that shows nanocrystalline materials need not be brittle. It is shown that bulk thermoelectric materials with superior properties can be produced by the ball milling and consolidation of powders to provide an ultrafine grain structure.

Ni57Zr22X8Nb8Al5 (X = Ti, Cu) metallic glass (MG) and nanocomposite powders were synthesized by mechanical alloying. Outstanding differences in glass-forming ability (GFA), thermal property, particle size and crystallization behavior were found for the two synthesized alloy powders with different alloying substitutions. The Ti-containing MG powder exhibits better GFA, higher thermal stability, lower enthalpy of crystallization and smaller particle size compared with the Cu-containing nanocomposite powder, respectively. Meanwhile, the crystallization of the Ti-containing MG powder is governed by typical volume diffusion-controlled three-dimensional growth. The better GFA for the Ticontaining alloy system could be explained by appropriate atomic-size mismatch and large negative heat of mixing among main constituent elements. The higher enthalpy of crystallization for the Cu-containing nanocomposite powder leads to the lower thermal stability and larger particle size of the powder than Ti-containing MG powder. [doi:10.2320/matertrans.M2013184]

Intrinsic relationship between crystallization mechanism of metallic glass powder and microstructure of bulk alloys fabricated by powder consolidation and crystallization of amorphous phase

This paper focuses on the optimization of ball milling as a dry mixing method and comparison with the wet method for manufacturing phenolic/multi-wall carbon nanotube (MWCNT) composites. In the ball milling, the effect of milling-time on the properties of composites containing functionalized and pristine MWCNT in two MWCNT concentrations has been investigated. At first in the wet method, polymer was dissolved in acetone and then mixed with MWCNT by sonication method. Also, the effect of functionalization by use of acid nitric refluxing was considered. The material properties were characterized by the DSC, FTIR, Raman, electrical conductivity, SEM, TEM and bending strength analyses. The results of electrical conductivity and bending tests showed that the best time for ball milling is about 2 hrs. In addition, functionalization had a positive effect on bending strength and a negative effect on electrical conductivity. The results of DSC indicated that the composite manufactured by ball milling method resulted in more thermal stability than that manufactured by the wet method. It was also shown that the functionalization increases the thermal stability; however, the increasing MWCNT concentration leads to agglomeration, thereby decreasing the thermal stability.

Synthesis of Mg–Zn–Ca metallic glasses by gas-atomization and their excellent capability in degrading azo dyes

Mechanical alloying characteristic and thermal stability of Al78Fe20Zr2 amorphous powders

Amorphous alloys have emerged as an important class of advanced materials that own a combination of properties, such as mechanical strength, hardness, high elasticity modulus and a very good corrosion resistance. Since the number of amorphous structures alloys increased in the last decades, ways of joining such materials were studied in order to produce complex structures or increase their size. Thus, if this kind of complex products are obtained, it will diversify their applicability in multiple and various domains. For this research two ways of joining amorphous ribbons has been studied: solid state welding and radiant energy welding. For the radiant energy welding process, it was selected electron beam welding (EBW) method and for the solid-state welding process, ultrasonic welding (UW) method was chosen. Seeing that these methods have found applicability in industries, a comparative study was done in order to see which one offers the best outcome. Recently, in the last years, such products were embedded in a polymer matrix, creating thus, composite materials that have improved mechanical properties. This raised curiosity for major industries, such as aero-space, medical and automotive. Amorphous ribbons from Ni-Fe-Cr-Si-B and Al-Ni-Nd-Co alloy families were welded by EBW method, and Cu-Zr-Al amorphous ribbons were welded by the UW method. Microstructure characterization has been performed by SEM, EDX, XRD and DSC analyses.

The outstanding efficiency of Fe‐based metallic glass powders in degrading organic water contaminants is reported. While the glassy alloy contains 24% chemically inactive metalloid elements, the powders are capable to completely decompose the C32H20N6Na4O14S4 azo dye in aqueous solution in short time, about 200 times faster than the conventional Fe powders. The metastable thermodynamic nature and the particle surface topography are the major factors controlling the chemical performance of the metallic glass. Our findings may open a new opportunity for functional applications of metallic glasses.

This study aims to investigate the microstructure and mechanical properties of Ti3SiC2-carbon nanofiber (CNF) composite materials by powder metallurgy (PM). Ti, SiC, graphite and CNF powders were used to produce Ti3SiC2-CNF composite materials. After formulated powders were ground in a ball mill, the milled powders were pressed at 500 MPa pressure and then sintered at 1150 °C, 1300 °C and 1450 °C. SEM-EDS and XRD analysis were used to examine the microstructure and phase formation. Hardness test was carried out with the help of Vickers hardness test apparatus. The densities were measured by Archimedes’ principle. Three-point bending test was performed to determine the transverse rupture strength (TRS) of the samples. SEM images showed that the samples have kink band and nanolaminar structures typical of MAX phase materials. The presence of Ti3SiC2 phase detected by XRD analysis also supports this situation. Depending on the sintering temperature, there were changes in the microstructure, density and mechanical properties of the samples.

The amorphous Cu46Zr42Al7Y5 alloy presents large supercooled liquid region (ΔTX = 100 K), with a viscosity of about 106 N.s/m2 where the material can flow as a liquid, making it possible an easy deformation in this temperature region. The aim of this work was to analyze processing routes to produce bulks of metallic glasses. Two kinds of materials were used: amorphous powders and ribbons, both were consolidated by hot extrusion in temperatures inside the range between Tg and Tx, with a ram speed of 1 mm/min and extrusion ratio of 3 : 1. Analysis of X-Ray Diffratometry (XRD), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM), revealed that the proposed consolidation routes were effective to produce large bulks of amorphous materials, even with the strong decreasing of ΔTX observed after deformation by milling and during extrusion.

The effect of ball-to-powder weight ratio on the fabrication of Nb-base powder via ball milling was studied. The structural evolution and morphology of the powders were investigated using LPSA, XRD and SEM techniques. The results indicate that increasing the BPR leads to decreases in particle size and grain size of powders. For a given milling time of 18 h and rotational speed of 250 rpm, ball milling with BPR of 20:1 produces an ultrafine powder with a mean particle size of about 2 μm and a grain size of about 20 nm. A 30:1 of BPR increases the useless collision frequency during ball milling, leads to a serious fraying of milling balls.

In this paper, a method of ball milling and sieving is proposed for recovery of high-grade copper from waste printed circuit boards (WPCBs). The effects of the milling time on the metals grade and recovery of the Cu, Sn and Pb during mechanical treatment were investigated. The results showed that, after 3 cycles of ball milling and sieving, the content of Cu was enriched to 94.72 wt.% from the initial 74.22 wt.% with a high recovery rate of 86.78%. Moreover, the contents of Sn and Pb were enriched to 28.27 wt.% and 18.86 wt.% from 10.13 wt.% and 6.63 wt.% in the by-products, respectively. However, excessive grinding occurred when the milling time was longer than 3 h and led to a sharp decrease in Cu recovery. The X-ray diffraction (XRD) patterns indicated that the metal phases mainly comprised pure Cu, Sn, Pb in the WPCB particles, while a Cu-Sn alloy was formed during the milling process, and the Cu-Sn alloy was also enriched in the tailings. The results presented here establish that ball milling and sieving is an alternative approach to recovering high-grade copper from WPCBs.