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Metals 2016,6, 218
definedas thehatchdistance (dH). Basedonparameteroptimizationandmanufacturerdata,dH,dP,
and twereset to80μm,65μm,and80μs, respectively. Thethicknessofeachpowder layerwasset
to 40μm. Finally, sampleswereproducedusingameander scanning strategyandby rotating the
scanningdirectionby67◦ aftereach layer.
Figure2.GeometryofSLMprocessedbars.
After removal fromthesteelbaseplate, the samplesweresectionedandmachined for further
analyses.Microstructuralobservationswerecarriedoutbyopticalmicroscope(LeicaMicrosystems,
RichmondHill,ON,Canada), andbyscanningelectronmicroscope (SEM,Oberkochen,Germany)
equippedwithenergydispersiveX-rayanalysis (EDX,OxfordInstruments,Abingdon-on-Thames,
UK)andelectronback-scattereddiffraction(EBSD,OxfordInstruments,Abingdon-on-Thames,UK)
detectors. SampleswerepreparedbystandardgrindingandpolishingfollowedbyetchingwithPicral
ormodifiedFry’s reagent.
Aging responseof theSLMsampleswasevaluatedstarting fromsamplesboth in theas-built
condition and after a standard solution treatment, carried out at 815 ◦C for 30min, followed by
waterquenching.
Differential scanningcalorimetry (DSC,LabsysSetaram,Caluire,France)analyseswerecarried
outontheas-builtandonthesolutiontreatedsamples (weightofabout50mg)bytemperaturescans,
at a rate of 20 ◦C/min inAratmosphere to assessprecipitation sequenceof strengtheningphases.
Isothermalagingcurves (hardnessvs. agingtimeatconstant temperature)were thencollectedat460,
490, 540, and600 ◦Cfor times ranging from10min,up to14days. Theevolutionofhardnesswas
followedbyperformingVickers indentationswitha loadof2kg.
X-ray diffraction (XRD) patterns were collected using a X-Pert PRO (PANalitical, Almelo,
TheNetherlands) instrument equippedwith aRTMSX′Celerator sensor. CuKα (k=0.15418nm)
radiationwas employed. Peaks identification andquantitative analysis of phaseswasperformed
byRietveldmethodusingMaudsoftware. Samples forXRDweresectionedbydiamondbladeand
polisheddownto1μmgrit size,applyingconventionalmetallographicmethods. Inorder toavoid
substantial structuralmodification, sampleswerecarefullypreparedbyaverygentleandprolonged
polishingstage.
Dog-bone tensile specimens having a gauge length of 20 mm and diameter of 4 mm were
machined frombars treated according to different conditions investigated. In the present study
only specimens built with their longitudinal axis oriented along the horizontal direction are
considered. Tensile testswereperformedat roomtemperaturewithacrossheadspeedof0.5mm/min
(corresponding to an initial strain rate of 4.2× 10−4·s−1) using aMTSAllianceRT/100universal
testingmachine(MTS,EdenPrairie,MN,USA).At least threespecimensforeachconditionweretested.
Finally, fractographicanalyseswerecarriedoutbySEMtoidentify themainfracturemechanisms.
76
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book 3D Printing of Metals"
3D Printing of Metals
- Title
- 3D Printing of Metals
- Author
- Manoj Gupta
- Editor
- MDPI
- Location
- Basel
- Date
- 2017
- Language
- English
- License
- CC BY-NC-ND 4.0
- ISBN
- 978-3-03842-592-2
- Size
- 17.0 x 24.4 cm
- Pages
- 170
- Keywords
- 3D printing, additive manufacturing, electron beam melting, selective laser melting, laser metal deposition, aluminum, titanium, magnesium, composites
- Categories
- Naturwissenschaften Chemie