Effect of Sm on thermal and mechanical properties of Cu-Zr-Al bulk metallic glasses (original) (raw)
Related papers
Sm Microalloyed Cu-Zr-Al Bulk Metallic Glasses
2016
The glass forming ability (GFA) and crystallization kinetics of rare earth (Sm) micro-alloyed Cu-Zr-Al based bulk metallic glasses were investigated using differential scanning calorimetry (DSC) under continuous heating conditions, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Under continuous heating conditions, the glass transition and crystallization temperatures were found to increase with increasing the isochronal heating rate. The activation energies for crystallization were calculated as 351.25 and 345.77 kJ/mol by means of Kissinger and Ozawa methods, respectively.
The morphology and mechanical properties of Zr59Nb5Cu18Ni8Al10 metallic glasses
2012
In the present work, the glass formation of Zr59Nb5Cu18Ni8 Al10 alloys of 2 mm diameter were prepared through casting in water cooled copper mould and in a ribbon form by the single roller melt spinning method. This study is primarily devoted to evaluate the results obtained by the two methods. The thermal stability was evaluated by differential scanning calorimetry (DSC) at a heating rate of 10 °C/mn. The glass formation, structural properties and morphology of the bulk metallic glass are presented, including glass transition temperature (Tg) and crystallization temperature (Tx). The microstructure and phases composition of the alloy have been analyzed using X-ray diffraction and indicate that the alloy is fully amorphous. The mechanical properties of bulk Zr59Nb5Cu18Ni8Al10 alloy is obtained by compression tests at room temperature. The fracture and morphologies after compression test are observed by Scanning Electron Microscopy (SEM), revealed the fragile plastic of the alloy. Th...
Glass formation and mechanical properties of (Cu50Zr50)100−xAlx (x=0, 4, 5, 7) bulk metallic glasses
Journal of Alloys and Compounds, 2009
The effect of Al content on the glass formation and mechanical properties was studied for (Cu 50 Zr 50) 100−x Al x (x = 0, 4, 5, 7) bulk metallic glasses. The crystallization temperatures of fully amorphous Cu 50 Zr 50 , Cu 48 Zr 48 Al 4 , Cu 47.5 Zr 47.5 Al 5 and Cu 46.5 Zr 46.5 Al 7 as-cast rods are 724 K, 753 K, 758 K and 782 K, respectively. The mechanical properties were investigated under compression at room temperature. As-cast Cu 46.5 Zr 46.5 Al 7 shows the highest yield strength (1867 MPa), whereas Cu 47.5 Zr 47.5 Al 5 shows the largest fracture strain of 11.2%. The fracture surfaces of the compressed samples were investigated by scanning electron microscopy and their morphology has been correlated with the compressive plasticity.
The crystallization behavior of melt-spun ribbons and bulk samples of the Cu 36 Zr 48 Al 8 Ag 8 glassy alloy on heating is presented here. The crystallization kinetics and structural changes in the Cu 36 Zr 48 Al 8 Ag 8 glassy alloy were studied using x-ray diffraction, transmission electron microscopy, differential scanning, and isothermal calorimetry methods. A clear comparison is made of the differences in the crystallization kinetics of the melt-spun ribbons and the copper-mold-cast bulk rod samples. It was suggested that the kinetics of crystallization in the rod sample, at any given temperature, are somewhat different than in the ribbon samples, probably because of size and free volume effects. Differences in the crystallization behavior of this alloy with other Cu-Zr-Al-Ag alloys have also been discussed.
Glass-Forming Ability and Ductility of Zr-Based and Al-Rich Bulk Metallic Glasses
Advanced Engineering Materials, 2008
The glass-forming ability and mechanical properties in the equivalent Zr-Al-CuNiCo three-component phase diagram was investigated as a function of Al content along the Zr 63-x Al x Cu 24 Ni 10 Co 3 (at.%) with 7 ≤ × ≤ 20 isoconcentration line. With a critical cooling rate of about 250 Ks-1 , the limit of bulk metallic glass formation was obtained at 16 at.% Al. Higher Al concentrations resulted in a composite amorphous/crystalline microstructure with varying crystalline volume fractions until at 21 at.% Al a fully crystalline alloy was obtained. Mechanical properties were investigated by nanoindentation and ultrasonic sound velocity measurements showing an increase in hardness and bulk modulus of the fully amorphous alloys as a function of the Al concentration. The ratio of the shear to the bulk modulus exhibited a pronounced minimum for 13 at.% Al. The mechanical and calorimetric data showed a unique correlation between the elatsic moduli, hardness, and the concentration dependence of the glass-transition temperature. The crystalline phase in the composite microstructure turned out to be brittle and, thus, no improvement in ductility was obtained. The early stages of solid-state amorphization by mechanical alloying of elemental powders of composition Zr 60 Al 10-Cu 18 Ni 9 Co 3 [1] were characterized by the formation of a variety of amorphous phases including some Al-rich compositions. [2] As such, it appeared interesting to find out if these
Comparison of mechanical behavior between bulk and ribbon Cu-based metallic glasses
Materials Science and Engineering: A, 2006
As-cast bulk and as-spun ribbon Cu 60 Zr 30 Ti 10 metallic glasses were characterized using differential-scanning calorimetry and instrumented nanoindentation. Two alloys show a significant difference in the amount of free volume, which is attributed to the difference in a cooling rate, while exhibiting a similar serrated plastic flow. Atomic-force-microscopy observations demonstrate the pile-ups containing shear bands around the indents in both alloys. The as-cast bulk alloy has higher hardness and elastic modulus than the as-spun ribbon alloy. The difference in the strengths of two alloys may be related to the different amount of free volume. The strength seems to be more sensitive to a cooling rate during solidification than the plastic-flow behavior in the Cu 60 Zr 30 Ti 10 .
Failure behavior of Cu–Ti–Zr-based bulk metallic glass alloys
Journal of Materials Science, 2009
Microstructure fracture and mechanical properties of Cu-based bulk metallic glass alloys were investigated. Centrifugal casting into copper molds were used to manufacture basic Cu47Ti33Zr11Ni9, and modified Cu47Ti33Zr11Ni7Si1Sn1 alloys. Although the alloys show an amorphous structure, TEM images revealed the formation of nanoparticles. At room temperature compression tests reveal fracture strength of 2000 MPa, elastic modulus of 127 GPa, and 1.8% fracture strain for the unmodified basic alloy. Whereas the modified alloy exhibits a fracture strength of 2179 MPa, elastic modulus reaches 123 GPa, and 2.4% fracture strain. So, with the addition of 1 at.% Si and Sn, the fracture strength improves by 9% and the fracture strain improves by 25%, but the fracture behavior under compression conditions exhibits a conical shape similar to that produced by tensile testing of ductile alloys. A proposed fracture mechanism explaining the formation of the conical fracture surface was adopted. The formation of homogeneously distributed nano-size (2–5 nm) precipitates changes the mode of fracture of the metallic glass from single to multiple shear plane modes leading to the conical shape fracture surface morphology.
Synthesis and mechanical properties of an amorphous Zr–Ni–Al–Cu alloy
Journal of Alloys and Compounds - J ALLOYS COMPOUNDS, 2006
Synthesis of bulk metallic glasses (BMGs) has been one of the hottest topics of research in materials science during this decade due to their very attractive physical and mechanical properties. In the present study, Zr64.5Ni15.5Al11.5Cu8.5 alloy has been synthesized from pure elements using Cu mold-casting technique. The alloy was designed to have e/a ratio = 1.3975 and average atomic size Ra = 0.1500 nm. Thermal properties were measured by performing DSC and supercooled liquid region ΔTx was found to be 94.9 K. Mechanical properties like microhardness, nanohardness, elastic modulus and fracture strength were measured. The fracture strength was found to be ∼1988 MPa. SEM examination shows vein-like patterns in the fractured compression-tested samples. Shear bands were observed and shear angle was found to be ∼36 ± 1° which is 6° less than that for most of the bulk metallic glasses to date without addition of fifth element.
Journal of Materials Research, 2006
Cu 46 Zr 47 Al 7 bulk metallic glass (BMG) and its composites in plate with different thicknesses up to 6 mm were prepared by copper mold casting. Primary crystallizing phases with different microstructures and volume fractions could be obtained under different cooling rates, forming some composites with different mechanical properties. Under compression tests, the 2-mm-thick monolithic BMG has a yield strength of 1894 MPa and a high fracture strength of up to 2250 MPa at plastic strain up to 6%, exhibiting apparent "work-hardening" behavior. The 4-mm-thick Cu 46 Zr 47 Al 7 BMG composite containing martensite phase yields at 1733 MPa and finally fails at 1964 MPa with a plastic strain of 3.7%.
MATERIALS TRANSACTIONS, 2007
A group of (Cu 47 Ti 34 Zr 11 Ni 8) 100Àx Si x (x ¼ 0; 1; 2; 3) bulk metallic glass forming alloys with diameter of 3 mm were prepared by watercooled copper mould cast. Microstructural investigations reveal that with increasing Si content the precipitated phases exhibit quite different morphologies, which varies from earthworm-like phase for alloys with x ¼ 1 to small-sized dendrite phase for alloys with x ¼ 2, and finally to developed dendritic phase for alloys with x ¼ 3. Room temperature compression tests reveal that a transformation from shear fracture to distensile fracture mechanism occurs for the samples with Si content over a critical value. For the alloys with x ¼ 0 and 1, fracture occurs in a shear mode with very high ultimate fracture strength. In contrast, the alloys with x ¼ 2 and 3 seem to fracture by a distensile mode with ultimate fracture strength greatly decreased. The fracture behavior of the as-cast alloys were investigated and discussed.