Evaluation of microstructural development in electron beam melted Ti-6Al-4V

In the current work an investigation of the microstructures of EBM built Ti-6Al-4V test bars has been performed using OM, SEM, TEM and XRD. It has been found that the prior beta phase, that formed during the initial solidification, possesses a column shaped morphology with growing direction parallel to built direction. Typical (alpha+beta) structures namely Widmanstatten alpha platelets with rod-like beta phase formed on the interfaces of the fine alpha grains, have been observed in the columnar prior beta grains. Grain boundary alpha phase was found to be formed around the boundaries of the columnar prior beta grains. Different phases present in the parts, especially the BCC beta phases have been characterized. The TEWEDX results indicate very high V composition in the beta phase. Results of TEWSAED and XRD also revealed that a superlattice structure could be present in the beta phase. Phase transformation sequence is discussed according to the processing history and the microstructures observed. (C) 2011 Elsevier Inc. All rights reserved.