CAREER: Surface Texturing of Bulk Metallic Glasses for Fabrication of Complex Micro Optics

Oklahoma State University, Stillwater OK

Investigators

Abstract

This Faculty Early Career Development (CAREER) grant will provide fundamental understanding of a novel technique to fabricate complex micro optics through generating surface textures on bulk metallic glasses. Micro optics with surface textures play a significant role in broad applications, such as automotive illumination systems, high-resolution display panels, diffraction gratings for laser systems, and reflective mirrors for traffic safety. Bulk metallic glasses have been increasingly used in fabricating micro optics due to high hardness, high corrosion resistance and no surface defects. However, micro optics produced with existing techniques using bulk metallic glasses usually have high fabrication cost, limited geometric accuracy and surface quality due to thermal deformations of the material. This Faculty Early Career Development (CAREER) award supports fundamental research of a novel technique to fabricate complex micro optics through generating surface textures on bulk metallic glasses by diamond machining with applied vibrations. The new technique will significantly reduce production cost, and improve component quality (both geometric accuracy and surface roughness). The award also supports activities to integrate research results into education, expose the public to precision manufacturing and optics engineering, and prepare next-generation engineers in advanced manufacturing areas. In the new technique, the planar vibration of the workpiece causes intermittent tool-workpiece contact, resulting in high-frequency variations of temperature and stress in material removal region. The first research objective is to uncover the relationship between amorphous-crystalline transition of bulk metallic glasses and temperature variation. It will be achieved by finite element modeling of the texturing process to predict temperature and amorphous-crystalline transition. The simulation results will be verified by measuring spatial-temporal temperature using a novel system combining a pyrometer and an infrared camera, and characterizing crystallization of the original amorphous microstructure through X-ray diffraction. The second objective is to determine the influences of stress variation in texturing process on deformation mode (inhomogeneous and homogeneous) of bulk metallic glasses. To achieve this objective, stress variation will be simulated through finite element method, and material deformation mode will be measured in-situ using acoustic emission signals. The third objective is to determine the effects of process parameters (tool geometry, texturing conditions, and vibration assistance parameters) on geometric accuracy of surface textures. The process dynamics including forced vibrations of tool and assisted vibrations of workpiece will be analytically modeled, and the simulated texture geometry will be experimentally verified using surface profilometer. Modeling and experiments for the three objectives will be conducted under various process parameters.