Active Slip Mode Analysis of an Additively Manufactured Ti-6Al-4V Alloy via In-Grain Misorientation Axis Distribution

Abstract

Selective laser-melted (SLM) Ti-6Al-4V alloy was quasi-statically compressed in the transverse and longitudinal directions at a strain rate of 1 × 10−3 s−1 at room temperature. The twinning, in-grain misorientation axis (IGMA) distribution and active slip modes of individual grains in the deformed SLM Ti-6Al-4V alloy were studied in detail via transmission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM). The α’/α phase was textured with the c-axis oriented either at ~45° or perpendicular to the building direction (BD). A combined analysis of the IGMA distribution and Schmid factor revealed that the prismatic slip or pyramidal slip was easily activated in the soft grains with their c-axes perpendicular to the BD (or the loading direction) in the longitudinal compressed sample, while slip was hardly activated in the transverse compressed sample due to the lack of soft grains. Prismatic slip with IGMA around Taylor axis also occurred in {10–11} twins. The observations revealed that the prismatic slip played a key role in accommodating the external strain and, thus, well explained the anisotropy of mechanical properties in the SLM Ti-6Al-4V alloy.

Keywords

• Ti-6Al-4V alloy
• additive manufacturing
• selective laser melted (SLM)
• in-grain misorientation axis (IGMA)
• anisotropy
• transmission Kikuchi diffraction (TKD)