Formation of nanostructure and mechanical properties of cold-rolled Ti–15V–3Sn–3Al–3Cr alloy

Microstructure evolution and mechanical properties of severe cold-rolled Ti–15V–3Sn–3Al–3Cr Ti-15-3 alloy were investigated and the formation of nanostructure was analysed by optical microscopy and transmission electron microscopy. Results show that fibrous microstructure with nanograins of below 100 nm is formed in the sheet of Ti-15-3 alloy with total thickness reduction of 80% by three passes cold rolling. The formation of nanostructure may be divided into three steps, firstly, formation of partial shear bands due to plastic instability; secondly, the crossing and refining of shear bands of different direction within the banded structure; thirdly, the forming of fibrous microstructure with nanograins. After three passes cold rolling and aging at 450 for 4 h, the ultimate strength of alloy can be increased to 1562 MPa. The strengthening of the alloy after aging mainly results from the abundant nucleation of nano-scaled α phase precipitated from the nano-sized β matrix.