(567f) Characterization of Spatial Variability in Material Properties in Echogenically-Segmented Metal Components Fabricated By Additive Manufacturing

The difference in thermal history during layer-by-layer manufacturing of metal components by selective laser melting (SLM) and related additive techniques may result in microstructural anisotropy and spatial variability in strength, density, porosity, and other material properties. The difference is particularly significant between interior and surface regions and in the build direction. While the microstructural variation may be characterized noninvasively by X-ray computed tomography, the options for nondestructive assessment of spatial heterogeneity in end-use material properties are lacking. This paper describes our progress towards the development of a novel approach to the ultrasonic characterization of spatially varying material properties and its application in additive manufacturing.

Statement of Contribution/Method

The traditional nondestructive ultrasonic evaluation gives an aggregate characterization of mechanical properties of solids and is insensitive to their spatial variabilities. This paper adapts the previously developed method for the ultrasonic measurements of segmental temperature distributions in solids [1–2] to estimate the spatial variability of mechanical properties in SLM-manufactured parts. We build upon the earlier report on assessing heterogeneity in additively manufactured aluminum parts [3] and describe our progress in designing echogenic features segmenting 3D printed parts without interfering with end-use functionality while improving the accuracy in segmental characterization.

Results

The application of the developed approach is demonstrated by characterizing segmental variability in the titanium-alloy and stainless-steel parts fabricated by SLM. Three echogenic features incorporated during the fabrication produce the train of echoes, the time-of-flight of which provides information which we use to assess the segmental variability in material properties. The ultrasonic results were found to correlate with the destructive characterization of mechanical properties. Overall, the experimental results indicate the feasibility of detecting heterogeneity of the material properties in 3D-printed parts following the developed approach.

[1] Y. Jia & M. Skliar, Energy & Fuels, 2016. [2] Y. Jia et al., Ultrasonics, 2016. [3] M. Roy, et. al., 2018 IEEE IUS, Kobe, Japan.