| Two Ni-Ti-Zr -based amorphous ribbons of compositions Ni56Cu2Zr18Ti16Al3Si5 and Ni36Cu23Zr18Ti14Al5Si4 were prepared by melt-spun techniques. Such pieces of ribbons were consolidated under the same conditions on Bridgman anvils using a pressure of 6 GPa at room temperature. Samples in the form of discs, 6.7 times thicker than the ribbons and about 10 mm in diameter, were produced by this high pressure torsion (HTP) process. XRD and TEM showed that the microstructure of the samples was dependent on the composition. The sample with the low Cu content revealed higher glass forming ability, thermal stability, tensile strength, Young's modulus, and hardness but partially crystallized during cold consolidation, while the sample with the high Cu content preserved the amorphous state. These results suggest that the thermal stability is not an indicator for retaining the amorphous phase in the HPT process. |
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