Achieving high strength and ductility in laser powder bed fusion-manufactured pure titanium through the addition of carbon nanotubes

The features of additive manufacturing (AM) have made commercially pure titanium (CP-Ti) an attractive candidate material for biomedical implants. However, achieving high strength and ductility is challenging because of the columnar structures and fine martensite formation. This study investigated the effect of carbon nanotubes (CNTs) addition on the microstructure and mechanical properties of grade 1 CP-Ti (Gr-1) during the laser powder bed fusion (L-PBF) process. A minute amount of 0.2% mass fraction (wt%) CNTs addition resulted in a high yield strength of approximately 700 MPa and exceptional ductility of 25.7%. Therein, a portion of the CNTs dissolved in the matrix as solute atoms, contributing to solution strengthening, while others were transformed into TiCx through an in situ reaction with the Ti matrix. Furthermore, the addition of CNTs resulted in the formation of a larger fraction of equiaxed grains and increased the activity of basal and prismatic slip systems. Hence, Gr-1 with CNTs exhibited significantly increased ductility while maintaining a high strength comparable to that of Gr-1 without CNTs. The insights gained from this study provide a novel approach for designing strong and ductile Ti alloys for AM. (sic)(sic)(sic)(sic)(AM)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(CP-Ti)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(CNTs)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(L-PBF)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(Gr-1)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)0.2% (wt%)(sic)CNTs, (sic)(sic)(sic)(sic)(sic)(sic)700 MPa(sic)(sic)(sic)(sic)(sic)(sic)25.7%(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic), (sic)(sic)(sic)CNTs(sic)C(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic);(sic)(sic)CNTs(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)TiCx.(sic)(sic), (sic)(sic)CNTs(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)Gr-1/CNTs(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)Gr-1(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).