Deformation evolution and fracture mechanism of porous TC4 alloy scaffolds fabricated using selective laser melting under uniaxial compression

Abstract

Porous TC4 alloy scaffolds (diamond and body centered cubic (BCC)) were successfully processed by selective laser melting (SLM), and a novel compression deformation behavior with a fracture mechanism has been investigated. When the diamond porous TC4 alloy scaffolds with large porosity were compressed, the stress–strain curve of the porous scaffolds increased and then decreased periodically, and the deformation spread symmetrically to both sides along with the 45° shear band of the inclined plane. In particular, while the BCC porous scaffolds with small porosity were compressed, the porous scaffolds’ compression deformation occurred at the lower part of the shear zone, and the stress-strain curve initially increased and then tended to a relatively stable stage. In addition, all the as-built porous TC4 scaffolds underwent brittle fracture, and the fracture surface of the BCC-type TC4 porous scaffolds was more regular than that of diamond scaffolds, which could be attributed to the BCC-type TC4 porous scaffolds without an obvious collapse. Two allotrope structures (hcp-α, bcc-β) of Ti caused a brittle fracture of the porous alloy scaffolds. Compared with the diamond scaffolds, the BCC porous scaffolds manufactured using SLM had smaller and regular α′ martensite, which indicated that the smaller and regular α′ martensite could improve the ultimate compressive strength of the BCC porous scaffolds.