Antibacterial copper-bearing titanium alloy prepared by laser powder b e d fusion for superior mechanical performance

Copper element was added in pure titanium to produce a new biomedical titanium-copper alloy by laser powder bed fusion(LPBF).Addition of copper can eliminate the mismatch of high strength but poor duc-tility problem caused by lathα’martensite,which is the usual microstructure of nearαtitanium alloy fabricated by LPBF.Instead of by the usual trade-offrelationship between strength and ductility,which is a long-standing challenge for martensitic titanium alloys,in this study,we proposed a boundary engineer-ing strategy and aim to synergistically enhance the strength and ductility of martensitic titanium alloy fabricated by LPBF.It is hypothesized that whilst both low-angle and high-angle grain boundaries are beneficial to the strength,high-angle grain boundary can simultaneously improve the ductility of materi-als.To test this strategy,a Ti-5Cu(wt.%)alloy is selected to compare against pure titanium and Ti-6Al-4V at the same laser processing conditions.EBSD,TEM and XRD analysis show that the as-fabricated LPBF Ti-5Cu alloy is comprised of partially tempered martensite with extraordinarily high number density of both high-angle and low-angle grain boundaries as well as low dislocation density.Such microstructure enables a high tensile strength of 940-1020 MPa,which is at a similar level as LPBF Ti-6Al-4V,and an excellent elongation of 13%-16%,twice as much as that of LPBF Ti-6Al-4V.The mechanism of microstruc-ture refinement in LPBF Ti-5Cu at different levels from prior-βgrains,martensitic packets,blocks to laths is also discussed.