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

• DOI: 10.1016/j.matdes.2017.12.037
• Publication Date: 2017-12-20T04:49:33Z
• Authors: Changjun Han; Yan Li; Qian Wang; Daosheng Cai; Qingsong Wei; Li Yang; Shifeng Wen; Jie Liu; Yusheng Shi
• Keywords: Acicular; Selective Laser Melting; Vickers hardness test; Lath

Abstract 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 × 10− 4 μm/μm2 to 2.7 × 10− 3 μm/μm2. 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 m1/2 to 0.88 MPa m1/2, which can be tailored to fit that of cortical and cancellous bones.