Novel Fabrication Routes of Metallic Micromembranes for In Situ Mechanical Testing

Abstract

A methodology to miniaturize mechanical tests of metal alloys based on membrane deformation was developed in this investigation. The buildup of this new path for miniaturization tests requires small amounts of material for testing. This is of particular interest for irradiated structural nuclear materials. Micrometric metallic circular membranes were fabricated starting from thin alloy foils and using two different paths. Serial fabrication of microspecimens was performed by means of successive focused ion beam (FIB) steps. On the other hand, high-throughput parallel fabrication was achieved by differential sputtering (DS) based on reactive ion etching followed by a final fine FIB polishing to flatten the membranes and straighten the mechanical response. Micro-punch tests were performed using spherical tips and the in situ load–displacement curves were recorded while monitoring the test in a scanning electron microscope. The values reached after testing of the DS membranes were more reliable than those of FIB samples, showing a large stretching section and higher values of maximum force (64 mN) and displacement (22.2 μm). The micro-punch testing methodology developed in this work combines the advantage of facilitating the interpretation of the mechanical response, by producing a bi-axial stress distribution during membrane stretching, while being amenable to high-throughput microspecimen fabrication.

Keywords

• microfabrication
• membranes
• focused ion beam
• differential sputtering
• micro-punch test