Five-parameter characterization of intervariant boundaries in additively manufactured Ti-6Al-4V

Additive manufacturing has emerged as a promising route to fabricate complex-shaped Ti-6Al-4V parts. The microstructural evolution and variant selection across builds in response to different printing strategies processed by electron beam powder bed fusion has been previously clarified. However, a detailed knowledge of the grain boundary plane characteristics of the alpha-alpha intervariant interfaces is still missing. The aim of this study was to reveal the full 'five-parameter' crystallographic characteristics of the intervariant boundaries. The most common alpha alpha intervariant for colony and basketweave microstructures was 60 degrees/[1 1 2 0], while in the acicular microstructure, the maximum was at 63.26 degrees/[10 5 5 3]. This is discussed in terms of self-accommodation during the 13 to alpha phase transformation, and the degree of coherence of the alpha laths in the as-deposited condition and during further growth. The grain boundary plane distributions reveal a high tendency for intervariant boundaries to terminate on prismatic and pyramidal planes rather than on low-energy basal planes. This suggests that, during additive manufacturing of Ti-6Al-4V and irrespective of the alpha morphology, the crystallographic constraints imposed by the Burgers orientation relationship determine the boundary plane distribution characteristics. (c) 2020 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).