Development of high ductility and adequate strength in pure titanium recycled from chips by multi-pass equal channel angular pressing

Abstract

Pure titanium chips were consolidated by a solid-state recycling process in the form of multi-pass equal channel angular pressing (ECAP) with the number of passes up to 16 passes. Electron backscatter diffraction reveals that low angle grain boundaries (with misorientation <15°) were substantially presented within coarse grains which were enclosed by high angle grain boundaries (=15°). Adequate yield strength (above 300 MPa) was achieved. It was contributed not only by high angle grain boundary, but also low angle grain boundary. At the same time, high ductility (with a uniform elongation up to 27%) is derived from the strain hardening owing to the existence of low angle grain boundaries and coarse grains. The mechanical properties of the recycled titanium are good enough to compare with those of the reference ingot subjected to the multi-pass ECAP.