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NSYSU

1. Lai, Yen-Huei. Effects of Sample Size on Various Metallic Glass Micropillars in Microcompression.

Degree: PhD, Materials and Optoelectronic Science, 2009, NSYSU

Over the past decades, bulk metallic glasses (BMGs) have attracted extensive interests because of their unique properties such as good corrosion resistance, large elastic limit, as well as high strength and hardness. However, with the advent of micro-electro-mechanical systems (MEMS) and other microscaled devices, the fundamental properties of micrometer-sized BMGs have become increasingly more important. Thus, in this study, a methodology for performing uniaxial compression tests on BMGs having micron-sized dimensions is presented. Micropillar with diameters of 3.8, 1 and 0.7 μm are fabricated successfully from the Mg65Cu25Gd10 and Zr63.8Ni16.2Cu15Al5 BMGs using focus ion beam, and then tested in microcompression at room temperature and strain rates from 1 x 10-4 to 1 x 10-2 s-1. Microcompression tests on the Mg- and Zr-based BMG pillar samples have shown an obvious sample size effect, with the yield strength increasing with decreasing sample diameter. The strength increase can be rationalized by the Weibull statistics for brittle materials, and the Weibull moduli of the Mg- and Zr-based BMGs are estimated to be about 35 and 60, respectively. The higher Weibull modulus of the Zr-based BMG is consistent with the more ductile nature of this system. In additions, high temperature microcompression tests are performed to investigate the deformation behavior of micron-sized Au49Ag5.5Pd2.3Cu26.9Si16.3 BMG pillar samples from room to their glass transition temperature (~400 K). For the 1 μm Au-based BMG pillars, a transition from inhomogeneous flow to homogeneous flow is clearly observed at or near the glass transition temperature. Specifically, the flow transition temperature is about 393 K atthe strain rate of 1 x 10-2 s-1. For the 3.8 μm Au-based BMG pillars, in order to investigate the homogeneous deformation behavior, microcompression tests are performed at 395.9-401.2 K. The strength is observed to decrease with increasing temperature and decreasing strain rate. Plastic flow behavior can be described by a shear transition zone model. The activation energy and the size of the basic flow unit are deduced and compared favorably with the theory. Advisors/Committee Members: Liu-Win Chang (chair), Shian-Ching Jang (chair), New-Jin Ho (chair), Chih-Ching Huang (committee member), Jinn-P. Chu (chair).

Subjects/Keywords: microcompression tests; sample size effect; metallic glass

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Lai, Y. (2009). Effects of Sample Size on Various Metallic Glass Micropillars in Microcompression. (Doctoral Dissertation). NSYSU. Retrieved from http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1116109-202132

Chicago Manual of Style (16th Edition):

Lai, Yen-Huei. “Effects of Sample Size on Various Metallic Glass Micropillars in Microcompression.” 2009. Doctoral Dissertation, NSYSU. Accessed February 23, 2019. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1116109-202132.

MLA Handbook (7th Edition):

Lai, Yen-Huei. “Effects of Sample Size on Various Metallic Glass Micropillars in Microcompression.” 2009. Web. 23 Feb 2019.

Vancouver:

Lai Y. Effects of Sample Size on Various Metallic Glass Micropillars in Microcompression. [Internet] [Doctoral dissertation]. NSYSU; 2009. [cited 2019 Feb 23]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1116109-202132.

Council of Science Editors:

Lai Y. Effects of Sample Size on Various Metallic Glass Micropillars in Microcompression. [Doctoral Dissertation]. NSYSU; 2009. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1116109-202132

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