Microstructure characterization in cast and 3D printed TiZrNb alloys

TiNbZr alloys exhibit excellent biocompatibility and mechanical properties that makes them good candidates for biomedical applications, particularly in orthopaedics and bone engineering. Manufacturing of metal parts of complex geometry (such as human bones, for example) results in significant material loss during machining of forged or rolled products. Thus, casting or additive manufacturing may be considered as the most promising technological processes. However, absence of deformation during casting and additive manufacturing may adversely affect the final microstructure and mechanical properties, due to low dislocation density, coarse grain structure, and unfavourable distribution of microalloying elements precipitates. This initiates investigation of the microstructure-properties relationship in novel Ti-alloys and its dependence on alloy composition and processing parameters.

This presentation outlines microstructure imaging and microanalysis techniques applied for investigation of cast and additively manufactured TiZrNb alloys. Correlation between optical, scanning electron and transmission electron microscopy allowed thorough characterisation of grain structure, phase balance, precipitation, and dislocation structure in four studied alloys. The single-phase cast alloy exhibited a larger grain size and lower dislocation density than these in a single-phase 3D printed alloys. In contrast, cast 2-phase Ti6Al4V alloy showed a much smaller grain size, 2 times higher dislocation density, and homogenously dispersed nano-sized precipitates. The effect of microstructural parameters on hardness of the tested alloys is discussed.