Seite - 123 - in 3D Printing of Metals

Metals 2017,7, 64 Figure 4. Pore size distribution in SLM samples, obtained from optical microscopy. Red curve represents thecumulativeporedistribution. However, theporeswerenotevenlydistributedthroughout thecutspecimensandsomeof them wereconcentratedmore incertainareascomparedtoothers. Itwasobservedthat for thesamplescut alongthex–yplane (alongthescandirection), theporesweremainlyconcentratedat theboundaryof the“island”whichwasemployedas thescanstrategyduringSLMinthisstudy(Figure5). Inother words, theporeswere locatedat theoverlappingareabetween two“islands”, similar to thework carriedoutbyGustmannetal. [30]. Interestingly,alignedporesappearedregularlyalongthebuild direction for the samples cut along the x–z and y–zplanes (Figure 6). This could be the result of inclusions suchasoxidespresentuponsolidificationof themoltenpool [31–33]. Nevertheless, the porositycontentat theseregionswithahighporosityconcentrationamountedupto~1.68%,which is still a smallfigureasawholebut is relativelyhigher thantheaverageporositycontentcalculated. Figure5.Micrographsshowingporositydistributionfor the (a)un-etchedand(b) etchedspecimencut alongthex–yplane. 123