Thermal and Microstructure Modeling of Metal Deposition Processes with Application to Ti-6Al-4V

Simple item page
dc.contributor.authorKelly, Shawn Michaelen
dc.contributor.committeechairKampe, Stephen L.en
dc.contributor.committeecochairBabu, Sudarsanam Sureshen
dc.contributor.committeememberReynolds, William T. Jr.en
dc.contributor.committeememberAning, Alexander O.en
dc.contributor.committeememberDavid, Stan A.en
dc.contributor.committeememberChristodoulou, Leonitusen
dc.contributor.departmentMaterials Science and Engineeringen
dc.date.accessioned2014-03-14T20:19:11Zen
dc.date.adate2004-12-03en
dc.date.available2014-03-14T20:19:11Zen
dc.date.issued2004-11-12en
dc.date.rdate2004-12-03en
dc.date.sdate2004-11-24en
dc.description.abstractLaser metal deposition (LMD) offers a unique combination of process flexibility, time savings, and reduced cost in producing titanium alloy components. The current challenge in processing titanium alloys using LMD methods is understanding the complex microstructure evolution as a part is fabricated layer by layer. The current work focuses on the characterization, thermal, and microstructural modeling of multilayered Ti-6Al-4V deposits. A thermal model has been developed using finite difference techniques to predict the thermal history of LMD processes. A microstructure model that predicts the alpha phase fraction and morphology evolution was constructed to quantify the effect of thermal cycling on the as-deposited microstructure evolution. Alpha dissolution and growth are modeled assuming one-dimensional plate dissolution according to a parabolic rate law, and a Johnson-Mehl-Avrami-Kolmorgorov (JMAK) nucleation and growth model, respectively. Alpha morphology (colony-alpha and basketweave-alpha) evolution is tracked using a simplistic approach. Characterization of the deposit has shown that a complex microstructure evolves consisting of a two distinct regions: a transient region of undeveloped microstructure and a characteristic layer that is periodically repeated throughout the deposit. The transient region contains a fine basketweave and colony-alpha morphology. The characteristic layer contains a two phase mixture of alpha+beta, with the alpha phase exhibits regions of colony-alpha (layer band) and basketweave-alpha morphology. The different regions of microstructural contrast in the deposit are associated with thermal cycling. The thermal model results show that a heat affected zone defined by the beta transus extends approximately 3 layers into the deposit. The phase fraction model predicts the greatest variation in microstructural evolution to occur in a layer n after the deposition of layer n+3. The results of the morphology model show that increased amounts of colony-alpha form near the top of a characteristic layer. It follows that a layer band (colony-alpha region) forms as a result of heating a region of material to a peak temperature just below the beta transus, where a large amount of primary-alpha dissolves. Upon cooling, colony-alpha forms intragranularly. The coupled thermal and microstructure models offer a way to quantitatively map microstructure during LMD processing of Ti-6Al-4V.en
dc.description.degreePh. D.en
dc.identifier.otheretd-11242004-211009en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-11242004-211009/en
dc.identifier.urihttp://hdl.handle.net/10919/29731en
dc.publisherVirginia Techen
dc.relation.haspartFigure_8_7_Morphology_Movie.moven
dc.relation.haspartSM_Kelly_Dissertation_Final.pdfen
dc.relation.haspartFigure_6_12_Temperature_Movie.moven
dc.relation.haspartFigure_4_10_Last_4_Layers_Movie.moven
dc.relation.haspartFigure_8_4_Phase_Fraction_Movie.moven
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectmicrostructure modelen
dc.subjectheat treatmenten
dc.subjectti-6al-4ven
dc.subjectmetal depositionen
dc.subjecttitanium alloyen
dc.subjectadditive manufacturingen
dc.subjectnear net shapeen
dc.subjectthermal modelen
dc.subjectrapid prototypingen
dc.titleThermal and Microstructure Modeling of Metal Deposition Processes with Application to Ti-6Al-4Ven
dc.typeDissertationen
thesis.degree.disciplineMaterials Science and Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

Files

Original bundle
Now showing 1 - 5 of 5
Name:
Figure_8_7_Morphology_Movie.mov
Size:
193.99 MB
Format:
Video Quicktime
Download
Thumbnail Image
Name:
SM_Kelly_Dissertation_Final.pdf
Size:
221.81 MB
Format:
Adobe Portable Document Format
Download
Name:
Figure_6_12_Temperature_Movie.mov
Size:
132.95 MB
Format:
Video Quicktime
Download
Name:
Figure_4_10_Last_4_Layers_Movie.mov
Size:
26.28 MB
Format:
Video Quicktime
Download
Name:
Figure_8_4_Phase_Fraction_Movie.mov
Size:
156.17 MB
Format:
Video Quicktime
Download

Collections

Doctoral Dissertations