Deformation-induced ambient temperature α-to-β phase transition and nanocrystallization in (α + β) titanium alloy

Ambient temperature α-to-β phase transition and nanocrystallization in the aged Ti-25Nb-3Mo-3Zr-2Sn titanium alloy was achieved by surface mechanical attrition treatment (SMAT The phase transition occurs at α/β interfaces and extends to a phase interiors with increasing strain. It is irreversible and diffusion controlled. The stressinduced increase of Gibbs energy and enrichment of Nb may cause a high order of lattice instability of the a phase adjacent to the α/β interfaces and compel the a phase to β phase. The presence of fine a needles in the aged alloy and the phase transition from α to β with increasing strain are viewed to play a crucial role in the subsequent nanostructuring. © 2009 Materials Research Society.