The microscale drilling performance of a Zr-based bulk metallic glass (BMG) is investigated in this paper. Crystallization, drill temperature, axial force, spindle load (SL), acoustic emissions (AE), chip morphology, hole diameter, and entry burr height are measured and analyzed with varying cutting speed and chip load. The progression of tool wear is assessed using stereo-microscopy techniques. At small chip loads, minimum chip thickness (MCT) is observed to shift cutting mechanics from a shear-dominated to a ploughing-dominated regime. Consequently, evidence of drill instability and larger burr height are observed. As drilling temperatures rise above the glass transition temperature, the BMG thermally softens due to the transition to a super-cooled liquid state and begins to exhibit viscous characteristics. In the tool wear study using tungsten carbide microdrills, rake wear is found to dominate compared to flank wear. This is attributed to a combination of a high rate of diffusion wear on the rake face as well as lower abrasion on the flank due to the decreased hardness from thermal softening-induced viscous flow of BMG.
Microscale Drilling of Bulk Metallic Glass
Mechanical Science and Engineering,
Department of Mechanical
Science and Engineering,
University of Illinois: Urbana-Champaign,
Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF Micro- AND Nano-Manufacturing. Manuscript received June 14, 2013; final manuscript received September 19, 2013; published online November 13, 2013. Assoc. Editor: Stefan Dimov.
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Zhu, J., Kim, H. J., and Kapoor, S. G. (November 13, 2013). "Microscale Drilling of Bulk Metallic Glass." ASME. J. Micro Nano-Manuf. December 2013; 1(4): 041004. https://doi.org/10.1115/1.4025538
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