Progress in Severe Plastic Deformation of Metastable Beta Ti Alloys

Abstract

Metastable β Ti alloys can undergo martensitic transformation under stress. It is shown that such stress‐induced martensitic transformation (SIMT) can significantly facilitate grain refinement by severe plastic deformation (SPD), achieving β grain sizes of 100 nm in β Ti alloys without SIMT. The martensitic α″ formed partitions the β grains and blocks dislocation movement, but undergoes reverse transformation back into β at large strains, leaving a pure β grain structure. The grain refinement can be further enhanced by increasing the strain rate to the order of 10–100 s−1, leading to β grains of <10 nm. SPD also has significant effect on the morphology of the α precipitates upon aging, trans..