Effect of chemical ordering on the deformation mode of Al-rich Ti-Al single crystals

Abstract

Abstract The effect of the Al concentration on the ordered structure and plastic behaviour of Al-rich Ti[sbnd]Al alloys was investigated using single crystals of Ti[sbnd]54.7 at.% Al and Ti[sbnd]58.0at.% Al. Short-range and long-range orders with an Al5Ti3-type superstructure based on the L1o ordered structure were observed in the as-grown Ti[sbnd]54.7at.%Al and Ti[sbnd]58.0at.% Al crystals respectively. After annealing at 500°C the superstructure developed markedly in both crystals. The chemical ordering strongly affected the yield stress, fracture strain and work-hardening rate through the change in the deformation mode. The increase in Al concentration suppressed activation of (a/2) 〈1bar;10]-type ordinary dislocations since an antiphase boundary (APB) was created in the A15Ti3-type superstructure behind moving dislocations. Since the APB was created by the motion of a〈101] superlattice dislocations but its energy is lower than that related to ordinary dislocations, ordinary dislocations are more immob...