Microcompression of Bulk Metallic Glass and Tungsten - Bulk Metallic Glass Composites

摘要

Recently, there has been tremendous interest in the size-dependent mechanical properties of materials, in particular, using various applications of the micrometer-scale uniaxial compression technique. In this technique, site- specific focused ion beam (FIB) milling is employed to fabricate micrometer sized compression specimens (micro-posts) from otherwise bulk material. These micro-posts are then tested in uniaxial compression using a flat punch indenter in a conventional nanoindenter. We apply this technique to examine the mechanical properties of bulk metallic glass (BMG) systems from two perspectives; micro-electro-mechanical systems, and tungsten (W)-BMG composite kinetic energy penetrators (KEP). The mechanical properties of Pd40Ni40P20 are found to be relatively free from scale effects approaching the micron size scale. There are, however, moderate increases in strength for micrometer sized, likely resulting from extrinsic factors such as local heterogeneities, pores, and/or other defects are able to act as points of stress concentrations. While the mechanical properties of monolithic amorphous alloys are well understood, local heterogeneities in W-BMG composites may affect the response of the composite. With this motivation, the micro-posts of the BMG are machined from the composite material using site-specific FIB milling. The mechanical properties of the BMG matrix are examined, and thus microcompression is used as a tool to relate local mechanical properties to the expected bulk response in these composites.