Achieving High Strength and Ductility in Laser Powder-Bed Fusion-Manufactured Pure Titanium Through the Addition of Carbon Nanotubes

Abstract

Additive manufacturing (AM) of commercially pure titanium (CP-Ti) is an attractive candidate material for biomedical implants. However, achieving both high strength and ductility has been a great challenge due to the formation of columnar structures and fine martensite. This study systematically investigates the effect of carbon nanotubes (CNTs) addition on the microstructure and mechanical properties of CP-Ti Gr-1 during the laser powder-bed-fusion process. A small addition of 0.2 wt. % CNTs resulted in a high yield strength of approximately 700 MPa and an exceptional ductility of 25.7%. The CNTs completely dissolved in the matrix as solute atoms for solute strengthening. Furthermore, the addition of CNTs resulted in the formation of a large fraction of equiaxed grains and increased activity of basal and prismatic slips. As a result, Gr-1 with CNTs exhibited significantly increased ductility, from 18.0 to 25.7%, while maintaining a high strength comparable to that of Gr-1. The insights from this study offer a novel approach for designing strong and ductile Ti-alloys for AM.

Keywords: pure titanium, Laser powder-bed fusion, carbon nanotubes, high strength-ductility