Ti-6Al-4V is an established material in laser-based powder bed fusion (LPBF) and shows a great importance in aerospace, medical and lightweight applications due to its high specific strength. Even many scientific publications are available, some relevant aspects of the microstructure-property relationship are still not explored and object of current investigations.

Due to its metallurgical nature and the high cooling rates during LPBF the microstructure of Ti-6Al-4V is typically composed of so called α’-martensite directly after manufacturing. Low elongation at break and weak performance under cyclic loading makes this microstructure not desired for application. Therefore, a further thermal post-processing is necessary to generate a favorable fine α/β-dualphase microstructure. The typical temperatures of this post-processing are in the range of the α/β-Transus temperature or even higher.

We present in our contribution a detailed microstructural analysis of easy-to-measure features in Ti-6Al-4V parts, which were produced by LPBF and subsequently heat treated at different temperatures including low temperature heat treatment (550°C), high temperature heat treatment (843°C) and hot isostatic pressing (920°C). The decomposition of α’-martensite during the precipitation reaction of β-Ti is studied and the microstructural features of the precipitation process – such as volume content, size and shape – are analyzed and linked to the resulting mechanical properties.

Furthermore, the microstructural differences for comparable treatments, which also result in remarkably different mechanical properties, are discussed by multi-variante statistical analysis for microstructural classification using different microstructural features (mean value) as well as their distribution characteristics (median value and standard deviation).

The presented results are part of the AMTwin project, which is funded by the Free State of Saxony, Germany.