Classification of Defect Types in SLM Ti-6Al-V4 by X-ray Refraction Topography

Abstract

Porosity in additively manufactured materials, such as laser powder bed fusion Ti-Al6-V4, can play an important role in their mechanical performance. Not only the total porosity but also the shape/morphology of the individual pores need to be considered. Therefore, it is necessary to determine the distributions of different defect types (especially fusing defects and keyhole pores) and their dependence on process parameters. We show that synchrotron X-ray refraction radiography allows analysis of large samples (up to several millimeters) without compromising the detectability of submicrometer defects. Correspondingly, a classification tool is introduced that is able to quantitatively distinguish defects such as keyhole pores and binding defects with a confidence level of 94 %, even when the shape cannot be discerned because of limited spatial resolution.

Damage tolerant design of additively manufactured metallic components subjected to cyclic loading: State of the art and challenges

“…An attempt to classify defects has been made by Laquai et al [164] using X-ray refraction techniques (see also [165][166][167]. Such techniques allow for the detection of extremely small defects (above around 1 nm), even below the resolution of synchrotron radiation computed tomography.…”

“…An expression of this point is the development of defect catalogues by ASTM [321] and ISO [322] which include imperfections such as porosity, unmelted material, layer defects, stop-start flaws, inclusions etc. [24,167]. The situation is reminiscent to the development of such catalogues for welds and castings.…”

Evolution of Damage in All‐Oxide Ceramic Matrix Composite After Cyclic Loading

“…As mentioned in the Sections 1 and 2.3, X‐ray refraction techniques are sensitive to defect orientation and can be used to classify such defects. [ 23 ] Figure shows the orientation‐dependent spatial distribution of the relative specific surface values ( C m / μ ) for three different load states (unloaded state, after 520 000, and after 1 020 000 load cycles) as 2D grayscale images (maps). The same sample section is shown in all six images.…”

Synchrotron X-ray refraction detects microstructure and porosity evolution during in-situ heat treatments

“…Some of the studies report on the evolution of defects during in-situ tensile tests [11,12]. Recently, the use of SXRR was extended to categorize the void population in laser powder bed fusion (LPBF) manufactured TiAl6V4 and LPBF IN718 materials [13][14][15].…”