| Summary: | 碩士 === 國立中山大學 === 材料科學研究所 === 96 === The mechanical properties and micro-forming of the Au-based bulk metallic glasses are reported in this thesis. The original ingots were prepared by arc melting and induction melting. The Au49Ag5.5Pd2.3Cu26.9Si16.3 bulk metallic glasses with different diameters 2 and 3 mm were successfully fabricated by conventional copper mold casting in an inert atmosphere. By the observation of transmission electron microscopy diffraction pattern, there are crystalline phases among the amorphous matrix phase.
The Au49Ag5.5Pd2.3Cu26.9Si16.3 bulk metallic glass shows the high glass forming ability and good thermal stability. By the Differential scanning calorimetry (DSC) results, the values ofΔΤx and ΔΤm are 50 and 21 K. And Trg, γ, and γm values for the Au49Ag5.5Pd2.3Cu26.9Si16.3
bulk metallic glass (BMG) at the heating rate of 0.67 K/s are 0.619, 0.430 and 0.774,
respectively.
The mechanical properties of Au49Ag5.5Pd2.3Cu26.9Si16.3 in terms of compression testing
are examined using an Instron 5582 universal testing machine. Room temperature
compression tests are conducted on specimens with various strain rates. To know the size
effect, the micro-pillars were made by using a focus ion beam (FIB) technique. The
micro-pillars were under the tests of compression at different strain rates, compared with
macro-scale 2 mm rod specimens. In contrast to the brittle fracture in a bulk sample, these
micro-pillar specimens show significant plasticity. The morphology of compressed pillar
samples indicates that the number of shear bands increased with the sample size and strain rates.
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