Titanium/hydroxyapatite (Ti/HA) gradient materials with quasi-continuous ratios fabricated by SLM: Material interface and fracture toughness

摘要

One of the first attempts on fabricating functionally graded materials (FGMs) of titanium/hydroxyapatite (Ti/HA) with quasi-continuous ratios by selective laser melting (SLM) was done. HA ratios varied among the layers of FGMs from 0 wt% to 5 wt% with 1 wt% gradient. The 3D reconstruction of Ti/HA FGM bulk with micro-pores was presented through micro-CT, and the percentage of micro-pore increased from 0.01% to 3.18% with the increasing of HA ratio. The scanning electronic microscope results showed that the crack was positively correlated to HA ratio with the crack density increasing from 1.5 x 10(-4) mu m/mu m(2) to 2.7 x 10(-3) mu m/mu m(2). The microstructure evolution from 0% to 5% HA ratios could be elucidated as long lath-shaped grains - long acicular-shaped grains - short acicular-shaped grains - continuous circle-shaped grains. quasi-continuous circle-shaped grains, due to the perturbation in the melting pool and obstruction of crystal development by HA. Accordingly, the FGM provides a wide range of nanohardness from 5.11 to 8.36 GPa and Vickers hardness from 3.42 to 5.67 GPa. Moreover, the fracture toughness from 2% to 5% HA ratios ranges from 3.41 MPa m(1/2) to 0.88 MPa m(1/2), which can be tailored to fit that of cortical and cancellous bones. (c) 2017 Elsevier Ltd. All rights reserved.