Mechanical behavior of porous commercially pure Ti and Ti–TiB composite materials manufactured by selective laser melting

Abstract

Commercially pure titanium (CP-Ti) and Ti–TiB composite parts with three different porosity levels (i.e. 10%, 17% and 37%) were produced by selective laser melting (SLM). Scanning electron microscopy (SEM) investigations show that martensitic (α′) microstructure exists in SLM-processed CP-Ti parts, whilst SLM-processed Ti–TiB composites present needle-shape TiB particles distributed in α-Ti matrix. Mechanical properties of these porous samples decrease with porosity level increasing. The yield strength and elastic modulus of porous CP-Ti parts range 113–350MPa and 13–68GPa respectively, which are much lower than those for porous Ti–TiB counterparts (234–767MPa and 25–84GPa respectively) mainly due to the strengthening effect induced by TiB particles in Ti–TiB samples. Compression stress–strain curves of 37% porous CP-Ti parts show a typical three-stage behavior of ductile porous metals. Also, the elastic moduli of both 37% porous CP-Ti and Ti–TiB samples are similar to that of human bone. SEM investigations of the porous CP-Ti samples after compression testing show that no crack presents until 50% compressive strain and most of deformation is absorbed by porous areas. In contrast, μ-CT investigations indicate that all porous Ti–TiB samples fail at early stages of compression testing due to cracks resulting from insufficient ductility of struts of porous areas, because they are not able to accommodate high strains of the deformation at high strengths.