Fully dense ≠ flawless
- defects due “under-melting” and generated by incomplete powder melting or improper fusion between successive tracks or layers.
- defects due to “over-melting” and caused by entrapment of gases or improper closure of a keyhole.
Influence of density on mechanical properties of SLMed Ti64
Rockwell Hardness Rc
Defects caused by insufficient energy input – typically large irregularities due to lack of fusion and presence of unmelted particles - have a strong bearing on the mechanical properties even when present in small amounts such as 1vol.%.
When the defects quantity increases to 5vol.%, the mechanical properties fall outside acceptable standard range.
Comparatively, defects caused by excessive energy input – typically small size symmetrical pores and voids due to over-melting effects - are less detrimental to part mechanical properties when present in low amounts up to 1vol.%
Yet, when the amount of these defects rises up to 5vol%, it catastrophically affects tensile, fatigue, and hardness properties.
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