Abstract
Precipitation of α 2 (Ti 3 Al) and β phases in the form of platelet or spherical particle in the α matrix of Ti-6Al-4V was observed after hydrogenation/dehydrogenation treatment at 600 °C. The crystallographic orientation relationship of α and α 2 was determined to be 〈 1 over(2, ̄) 1 0 〉 α ∥ 〈 1 over(2, ̄) 1 0 〉 α 2 and {0 0 0 1} α ∥{0 0 0 1} α2 . The nanoscale β phase precipitated in the α matrix was also observed, with their orientation relationships being {0 0 0 1} α ∥{1 1 0} β and 〈 1 1 over(2, ̄) 0 〉 α ∥ 〈 1 1 1 〉 β . The formation of α 2 and β phases can be attributed to the disproportionation effect. © 2006 Acta Materialia Inc.