The Role of Thermal Cycling on Twinning in Metastable Beta-Ti Alloy

Twinning in the Ti−26Nb (at.%) alloy during thermal cycle was investigated by TEM, and the interrelationship between displacive transformation and twinning was proposed. After 100 thermal cycles, fine {112}β 〈-1-11 〉β twins and preferentially formed ω particles were observed in the β matrix. The {112 }β〈-1-11〉β twins may nucleate in such ω particles and grow by merging of twin embryos. Further increasing the cycle number to 500, the {332}β〈11-3〉β twins bounded with laminated α" martensite were observed instead. The interfacial twin boundary α" phase mediates the martensitic transformation of the adjacent region and lead to {332}β〈11-3〉β twin formation.