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.
