OM data 2020

Here, we are using three different EB PBF scan strategies: linear scan (LS), ordered spot scan (OS), and random spots scan (RS) to fuse the widely used Ti-6Al-4V powder (Ti64). The change in scan strategies and therefore the thermal gradients create variation in the defects within the microstructure of the material. Such variations can be analyzed using optical microscopy (OM).

After standard metallography sample preparation, imaging was performed using an Olympus DSX510 optical microscope on 5x magnification to characterize the entire surface of each sample with sufficiently high image resolution. High magnification images of the entire surface with smaller field-of-view were first taken step-by-step and subsequently stitched together. Samples were then etched to reveal the underlying microstructure to compare to existing EBSD scans to compare the grain structure exhibited from using different techniques.

Using image processing (MIPAR) software, AM build defects were identified, quantified, and exported to a coding language for further data analysis. The code translates the provided quantitative data and generates histograms for eccentricity (roundness of defects), orientation (with respect to the positive x-axis), and caliper diameter (size), site-specifically. This allows to analysis the spatial distribution of defects, e.g., difference between defects in the center of the build vs. edge defects in each sample.