Abstract
β-Ti alloys have attracted considerable attention as new biomedical shape memory alloys. Given the critical importance of the plastic deformation in the martensite phase for the shape memory effect and superelasticity, we investigated here the plastic deformation behaviour of a single crystal of α″ (orthorhombic) martensite of Ti-27 mol%Nb shape memory alloy obtained by the stress-induced martensitic transformation of a single crystal of the parent β phase. Four operative plastic deformation modes were observed, including two dislocation slips and two twinnings. To the best of our knowledge, two of these plastic deformation modes (one dislocation slip and one twinning) were discovered for the first time in this study. The identified slip and twinning systems in the martensite phase have corresponding slip and twinning systems in the parent β phase with which they share many similarities. Therefore, we believe that the plastic deformation of the α″ martensite is inherited from that of the parent β phase.
Highlights
Masaki Tahara1,2, Nao Okano3,4, Tomonari Inamura1,2 & Hideki Hosoda1,2 β-Ti alloys have attracted considerable attention as new biomedical shape memory alloys
Given the critical importance of the plastic deformation in the martensite phase for the shape memory effect and superelasticity, we investigated here the plastic deformation behaviour of a single crystal of α′′ martensite of Ti-27 mol%Nb shape memory alloy obtained by the stress-induced martensitic transformation of a single crystal of the parent β phase
The plastic deformation of metastable β-Ti alloys in the β phase has been systematically investigated by many researchers33–38, in particular the effect of the loading orientation, test temperature and alloy composition on the main plastic deformation modes (i.e. dislocation slip with a Burgers vector b parallel to b and {332}b⟨113 ̄⟩b twin, with the subscript ‘b’ denoting the parent β phase) in single-crystalline samples
Summary
While a lot of effort has been dedicated to increasing the critical stress for plastic deformation, there have been only a few reports on the plastic deformation modes in Ti base SMAs. The plastic deformation of metastable β-Ti alloys in the β phase has been systematically investigated by many researchers, in particular the effect of the loading orientation, test temperature and alloy composition on the main plastic deformation modes (i.e. dislocation slip with a Burgers vector b parallel to b and {332}b⟨113 ̄⟩b twin, with the subscript ‘b’ denoting the parent β phase (bcc)) in single-crystalline samples. Single-crystalline α′′ martensite of Ti-27 mol%Nb was obtained here by a stress-induced martensitic transformation from a single crystal of the parent β phase, and its plastic deformation behaviour in terms of crystallographic orientation dependence and deformation modes was systematically investigated
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