Laser Polarimeter for Mapping and Assessment of Microtextures in Titanium Alloys

Advanced Optical Technologies, Inc. (AOT) will build a new type of optical crystallographic NDT sensor under a Phase II SBIR contract with the AFRL Materials & Manufacturing Directorate, WPAFB, OH. The new sensor, a laser polarimeter implementing AOT's patented polarization-classification imaging (PCI) techniques, will be the first to allow affordable quantitative grain-orientation imaging over large areas of titanium alloys at practical working distances in air. PCI is an extension of conventional polarized-light microscopy that provides crystallographic orientation. The sensor's parallel architecture enables large FOV and high speed compared to scanning sensors like electron backscattering diffraction (EBSD) and spatially-resolved acoustic spectroscopy (SRAS), which are more expensive than AOT's sensor. The AOT sensor would extend crystallographic NDT to more stages of titanium production and manufacturing, particularly for high-performance aerospace parts. The current standard for quantitative crystallography, EBSD, requires sectioning parts into small pieces to fit into a vacuum chamber and many hours of polishing to obtain orientation images in a microscope. AOT's sensor would alleviate the need to cut/destroy the test part and reduce the amount of polishing required; a collaborative study with EBSD experts at Sandia National Labs showed that PCI can obtain orientation images on samples too rough for EBSD.