Multiple-stage transformation behavior of Ti49.2Ni50.8 alloy with different initial microstructure processed by equal channel angular pressing

Multiple-stage transformation of Ti49.2Ni50.8 alloy processed by equal channel angular pressing (ECAP) was investigated as a function of pass number and aging treatment before ECAP. When the pass number is no more than four passes, three stage transformation, namely A→R, R1→M1 and R2→M2, occurs in the as-ECAP processed alloy initially aged at 450 °C for 60 min. Only the A→R→M forward transformation occurs provided that the aging duration was decreased/increased to 10/600min. The transformation sequence was discussed based on the microstructure evolution of as-ECAP processed alloy with different initial microstructure and pass number.