| Popis: |
We have investigated the effects of deformation temperature in the range from room temperature to 873 K on as-deformed and post-aging microstructures, and tensile properties after aging, for Ti-15V-3Cr-3Sn-3Al.In solution-treated conditions, slight cold deformation tends to form planar slip bands composed of extremely localized straight dislocations in β phase, because of the restriction of both cross-slip and secondary slip. The planar slip bands consequently cause the directional microstructure with α precipitates to align on the bands after aging. The tendency for straight dislocations obstinately persists even after a heavy cold deformation of about 60%. A directional distribution of rather coarse α precipitates is thereby brought about after aging in a heavily cold deformed material as well.On the other hand, cross-slip and secondary slip are both activated with increasing deformation temperature, to diminish the microstructural directionality. A fairly non-directional uniform distribution of finer α precipitates is attained through deformation at 873 K.The balance of strength and ductility of Ti-15V-3Cr-3Sn-3Al can be pronouncedly enhanced by the microstructural improvement.Cross-slip promoted at elevated temperatures was expected to be due to not only the thermal activation of itself, but also the reduction of athermal ω phase as its inhibitor. |
