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Progress in Severe Plastic Deformation of Metastable Beta Ti Alloys
Author(s) -
Zafari Ahmad,
Xia Keg
Publication year - 2020
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201900471
Subject(s) - materials science , equiaxed crystals , acicular , diffusionless transformation , metallurgy , metastability , dislocation , martensite , grain size , severe plastic deformation , deformation (meteorology) , stress (linguistics) , crystallography , composite material , microstructure , linguistics , physics , philosophy , chemistry , quantum mechanics
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 <50 nm, compared with >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, transforming it from acicular to equiaxed. Although the α nucleus formed between recrystallized β grains of <≈10 nm follows the Burgers orientation relationship (BOR), the semicoherent interface is lost upon β grain growth during aging, causing its growth into equiaxed shape.