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

The evolution behavior of alpha lamellae and evolution relationship between alpha lamellae and beta phase in TC17 alloy during isothermal heating and subsequent compression were investigated. The results show that the alpha/beta interface of TC17 alloy is made up of stable terrace plane and movable ledge plane. The ledge plane migrates along the length direction of alpha lamellae during isothermal heating, which results in rapid decrease of length and slow decrease of thickness of alpha lamellae. During compression, the continuous dynamic recrystallization (CDRX) are the main evolution mechanism of alpha and beta phases. The slip systems of beta phase are easily activated and the slip in beta phase (i.e. (110)[111]) will promote the slip in alpha phase (i.e. (0001)[1120]) at the initial stage of compression. Thus the CDRX of beta phase is preferentially initiated by more activated slip and it will promotes the CDRX of alpha phase, then the HABs are formed in alpha lamellae. Meanwhile, the beta stabilized elements Cr and Mo diffuse into the alpha/alpha boundaries in a short-time deformation. The alpha ->beta phase transformation is promoted by the enrichment of Cr and Mo elements and finally the alpha lamellae are separated with further compression.