Abstract
Severe plastic deformation in the form of equal channel angular pressing (ECAP) has been adopted to introduce severe shear strain into a Ti-20 wt.% Mo β-type titanium alloy to elucidate the aging response of the severely deformed β matrix. Upon isothermal aging in the (α + β) phase field, selective heterogeneous α nucleation and growth resulted in a mixed precipitation microstructure. An ultrafine-duplex (α + β) structure composed of equiaxed α precipitates formed inside the shear bands (SBs) created during ECAP, whereas acicular α precipitates were favoured outside the SBs. This distinct precipitation structure has been correlated to the structural characteristics of the SBs: high disorder with dislocation cells characteristic of low-angle boundaries and enhanced atomic diffusivity. The highly disordered structure results in a weak variant selection and thereby promotes randomly orientated α precipitation without obeying the Burgers orientation relationship. Furthermore, the enhanced atomic diffusivity facilitates rapid growth of the α nuclei to form the ultrafine-duplex (α + β) structure.
Original language | English |
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Pages (from-to) | 5067-5078 |
Number of pages | 12 |
Journal | Acta Materialia |
Volume | 60 |
Issue number | 13-14 |
DOIs | |
Publication status | Published - Aug 2012 |
Externally published | Yes |
Keywords
- β titanium alloy
- Precipitation
- Severe plastic deformation
- Shear bands
- Ultrafine-grained materials