Statistical Analysis of the Distribution of the Schmid Factor in As-Built and Annealed Parts Produced by Laser Powder Bed Fusion

Abstract

This study documents a systematic analysis of the global Schmid factor for different deformation mechanisms in α′/α and β-grains in different forms of direct metal laser sintered (DMLS) Ti6Al4V(ELI) based on EBSD data. A novelty of this study is the use of these data to calculate the values of the Schmid factor and the subsequent determination of their distribution and frequency, which, when compared to the slip systems of crystal structures, helps in determining the favourable slip systems in play. Both retained β-grains and reconstructed prior β-grains were considered in this analysis. The reconstruction of the prior β-grains was executed using the Automatic Reconstruction of Parent Grain for EBSD data (ARPGE) program. The distribution of the global Schmid factor for these Ti6Al4V phases was calculated using the MATLAB-based MTEX toolbox program. This analysis of deformation modes in the α′/α-phase was based on a uniaxial load state acting on the x, y, and z axes, while only the load along the build direction (x-direction) was considered in the analysis of deformation mechanisms in the β-phase of the alloy. The results of this study showed that the DMLS build direction influenced the distribution of the global Schmid factor for the basal slip system of α′/α-grains in as-built specimens and those samples that were heat treated below the α→β transformation temperature.

Keywords

• direct metal laser sintering
• Ti6Al4V(ELI)
• EBSD
• Schmid factor
• prior β-grains
• α′/α-grains