Microstructure Evolution and Deformation Mechanism of Ti‐55531 Alloy During Hot‐Rolling Process

Ti‐55531 alloy is a novel near‐β‐Ti alloy, which has promising application potential as critical aircraft components due to its outstanding mechanical properties. In this work, it is aimed to tailor the microstructure and mechanical properties of Ti‐55531 alloy by hot‐rolling in α + β‐phase field. In experimental results, it is indicated that an increasing number of α lamellae becomes globular or ellipsoidal shape with the increase of rolling reduction. As a result, the strength and elongation of the rolled samples continually increase. Lath‐like substructures are observed inside some residual lamellar α after 20% rolling reduction. Nearly all lath‐like substructures have their habit plane corresponding to (100)_α and exhibit the orientation relationship (OR) of [0001]_HCP //[001]_FCC, [20]_HCP //[]_FCC, and (100)_HCP //(_FCC with α phase. At high rolling reductions, the face‐centered cubic (FCC) substructures disappeared. Instead, {101} twin structures are frequently observed in lamellar α grains, indicating that both {101} twinning and martensitic transformation can be activated in Ti‐55531 alloy to accommodate the applied rolling deformation. To the authors’ knowledge, such stress‐induced martensitic transformation has not been reported before in Ti‐55531 alloy. Therefore, the findings in this work should advance the understandings on the deformation behavior and mechanism in this alloy.