Electron Beam Melting of Porous Titanium Alloys: Microstructure and Mechanical Behavior

Electron beam melting (EBM) is a relatively new rapid, additive manufacturing technology which is capable of fabricating complex, multi-functional metal or alloy components directly from CAD models, selective melting of precursor powder beds. Compared with Ti-6Al-4V samples with same porosity level, the EBMproduced β-type Ti-24Nb-4Zr-8Sn (Ti2448) porous components exhibit a higher normalized fatigue strength owing to super-elastic property, greater plastic zone ahead of the fatigue crack tip and the crack deflection behavior. The super-elastic property can be improved by increasing porosity of porous samples as a result of increasing the tensile/compressive stress ratio of the porous structure. EBM-produced components exhibit more than twice the strength-to-modulus ratio of porous Ti-6Al-4V counterparts. The position of fatigue crack initiation is defined in strain curves based on the variation of the fatigue cyclic loops. The unique manufacturing process of EBM results in the generation of different sizes of grains, and the apparent fatigue crack deflection occurs at the grain boundaries in the columnar grain zone due to substantial misorientation between adjacent grains.

Keywords: Electron beam melting, Mechanical properties, Microstructure, Porous material, Titanium alloys.