Continuous compression behaviors of selective laser melting Ti-6Al-4V alloy with cuboctahedron cellular structures

Cellular structures often show fluctuating stresses in compression stress-strain curves. Such fluctuating stresses correspond to strut fractures. In this study, the cellular Ti-6Al-4V alloy with cuboctahedron structure was prepared by selective laser melting. The cuboctahedron cellular structures showed reduced fluctuations in their compressive stress-strain curves after the initial yielding peak. Their moduli were modulated via the porosity of the structure by changing the strut diameter. A compressive modulus of between 1.3 and 4.868 GPa can be achieved by varying the porosity in the cellular structures between 33% and 84%. Both heat treatment and hot isostatic press (HIP) treatment reduced the fracture strength of the struts during compression due to the conversion of the alpha' martensite phase into the more ductile alpha + beta phase. The cellular structure with HIP treatment produced a continuous stress-strain curve during compression, indicating uniform strain distribution behavior. The continuous compressive stress-strain curve can lead to reduced debris formation during compression processes. The deformation showed either bending or stretching mechanisms depending on whether the supports were included along the building direction. The design concepts of cellular structures demonstrated in this study will be valuable in future biomedical applications.