Deformation Failure of Regular Porous Titanium with Different Porosities

Regular porous titanium specimens with different porosities was fabricated to investigate the overall and local failure characteristics of porous metals. Dynamic compression tests were implemented using the split Hopkinson pressure bar system at the strain rates from 600 s^-1 to 2100 s^-1. Results show that the specimens with different porosities exhibit two typical deformation modes: compression deformation mode and connected fracture mode. The compression deformation mode mainly occurs in the specimens with low porosity, and the characteristic is that the cell walls of outer surface of the specimen exhibit local collapse. However, the connected fracture mode mostly occurs in the specimens with high porosity, and usually shows connected fracture in one or more pore layers. Moreover, the local pores of two deformation modes present different characteristics during compression, and the stress concentration occurs at the position with the minimum curvature of the pores. Microstructural analysis indicates that shear band appearing in the intercellular walls is the main failure mechanism of the specimens. Dimples and ductile stripes of fracture surface reveal that the collapse of the intercellular wall is a process of ductile fracture. Meanwhile, the softening failure of the cell walls and the strain hardening of the matrix material can affect the mechanical response of porous titanium. Additionally, with the increase of porosity, the greater the stress concentration factor, the easier the failure of porous metals.