Subsurface Residual Stress Analysis in Ti-6Al-4V Additive Manufactured Parts by Synchrotron X-ray Diffraction

Speaker:
Mishurova, Tatiana; BAM Bundesanstalt fur Materialforschung und -prufung; Germany

Authors:
Mishurova, T.; Federal Institute for Materials Research and Testing (BAM); Germany
Artzt, K.; Institute of Materials Research, German Aerospace Center; Germany
Cabeza, S.; Institut Laue-Langevin; France
Requena, G.; Institute of Materials Research, German Aerospace Center; Germany
Bruno, G.; Federal Institute for Materials Research and Testing (BAM); Germany
Haubrich, J.; Institute of Materials Research, German Aerospace Center; Germany

ID: ECNDT-0213-2018
Download: PDF
Session: Additive Manufacturing – characterisation
Room: H1
Date: 2018-06-11
Time: 15:40 - 16:00

Synchrotron X-ray diffraction is a powerful non-destructive technique for the analysis of the material stress-state. High cooling rates and heterogeneous temperature distributions during additive manufacturing lead to high residual stresses. These high residual stresses play a crucial role in the ability to achieve complex geometries with accuracy and avoid distortion of parts during manufacturing. Furthermore, residual stresses are critical for the mechanical performance of parts in terms of durability and safety.
In the present study, Ti-6Al-4V bridge-like specimens were manufactured additively by selective laser melting (SLM) under different laser scanning speed conditions in order to compare the effect of process energy density on the residual stress state. Subsurface residual stress analysis was conducted by means of synchrotron diffraction in energy dispersive mode for three conditions: as-built on base plate, released from base plate, and after heat treatment on the base plate. The quantitative residual stress characterization shows a correlation with the qualitative bridge curvature method. Computed tomography (CT) was carried out to ensure that no stress relief took place owing to the presence of porosity. CT allows obtaining spatial and size pores distribution which helps in optimization of the SLM process.
High tensile residual stresses were found at the lateral surface for samples in the as-built conditions. We observed that higher laser energy density during fabrication leads to lower residual stresses. Samples in released condition showed redistribution of the stresses due to distortion.