| Summary: | 碩士 === 國立中央大學 === 材料科學與工程研究所 === 99 === Zr-based amorphous alloys have several attractive properties such as high strength, high hardness, good glass forming ability, and excellent ability of superplastic formation , so there is a development potential in MEMS and nanotechology. However the monolithic Zr-based amorphous alloys displays limited plasticity(0-0.5%) .
In this study, the plasticity of (Zr48Cu32Al8Ag8Ta4)99.25Sio.75 based bulk metallic glass composite (BMGc) of 4 at% in-situ Ta and 9 vol% ex-situ Ta increases up to 34%. The viscosity and hot plastic deformation in supercooling liquid region were done by thermal mechanical analysis (TMA) and hot compression test. According to the TMA results, the viscosity of the bulk metallic glass composite (BMGc) decreases with temperature increase, and there is a stable viscous flow occurs at 733 K. The results of hot compression test under different temperatures and strain rates shows the lowest flow stress was obtained in the lowest strain rate(5×10-2s-1) under 764 K . Analyze micro structure of the specimens after hot compression test by XRD and TEM to check the amorphous state. All results reveal their amorphous state even under the highest temperature and the lowest strain rate which are 764 K and 5×10-2 s-1 respectively.
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