The role of β phase in the morphology evolution of α lamellae in a dual-phase titanium alloy during high temperature compression

Abstract

The evolution behavior of α lamellae and evolution relationship between α lamellae and β phase in TC17 alloy during isothermal heating and subsequent compression were investigated. The results show that the α/β interface of TC17 alloy is made up of stable terrace plane and movable ledge plane. The ledge plane migrates along the length direction of α lamellae during isothermal heating, which results in rapid decrease of length and slow decrease of thickness of α lamellae. During compression, the continuous dynamic recrystallization (CDRX) are the main evolution mechanism of α and β phases. The slip systems of β phase are easily activated and the slip in β phase (i.e. (110)[1̅11]) will promote the slip in α phase (i.e. (0001)[112̅0]) at the initial stage of compression. Thus the CDRX of β phase is preferentially initiated by more activated slip and it will promotes the CDRX of α phase, then the HABs are formed in α lamellae. Meanwhile, the β stabilized elements Cr and Mo diffuse into the α/α boundaries in a short-time deformation. The α→β phase transformation is promoted by the enrichment of Cr and Mo elements and finally the α lamellae are separated with further compression.