Microstructure, mechanical properties, and fracture mechanism of As-cast (Ti0.5Cu0.25Ni0.15Sn0.05Zr0.05)100?x
Mo
x
composites |
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Authors: | G He W Löser L Schultz J Eckert |
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Affiliation: | (1) the Light Materials Group, National Institute for Materials Science, 305-0047 Ibaraki, Japan;(2) the Institut für Metallische Werkstoffe, IFW Dresden, D-01171, D-64287 Dresden, Germany;(3) the FG Physikalische Metallkunde, Technische Universitat, Darmstadt, Germany |
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Abstract: | Copper mold cast cylinders of (Ti0.5Cu0.25Ni0.15Sn0.05Zr0.05)100−x
Mo
x
composites are prepared. Addition of Mo in the bulk glass-forming alloy induces the formation of a dendrite/matrix composite.
For 3-mm-diameter cylinders, the matrix exhibits a homogenous ultrafine microstructure for Mo content of 2.5 at. pct, and
a fine eutectic microstructure for 5 at. pct Mo. For 5-mm-diameter cylinders, the matrix exhibits a dendritic microstructure
for 2.5 at. pct Mo, and exhibits a coarser eutectic microstructure for 5 at. pct Mo. Despite the formation of a dendrite/nanostructured
matrix composite in the cylinders, the quenched surface layer with a nanoscale grain size dominates the deformation and fracture
of the 3-mm-diameter cylinders. More than 56 vol pct quenched layer leads to a distensile fracture mode and the samples exhibit
high fracture strength and high Young’s modulus but low ductility. For 5-mm-diameter cylinders, the composite microstructure
becomes dominant due to its more than 64 vol pct volume fraction leading to a cone-shaped fracture surface. The samples exhibit
lower yield strength and lower Young’s modulus but better ductility compared to the 3-mm-diameter cylinders. The mechanical
behavior of the Mo-bearing composites strongly depends on the microstructural homogeneity and casting defects formed upon
solidification. |
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Keywords: | |
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