The Effect of Process Variables on Microstructure in Laser-Deposited Materials

The Effect of Process Variables on Microstructure in Laser-Deposited Materials

Bibliographic Details
Main Author: Bontha, Srikanth
Language:English
Published: Wright State University / OhioLINK 2006
Subjects:
Laser Deposition
Ti-6Al-4V
Microstructure
Rosenthal Solution
Solidification Map
Finite Element Modeling
Transient Effects
Distributed Heat Source
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=wright1160133069
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spelling ndltd-OhioLink-oai-etd.ohiolink.edu-wright11601330692021-08-03T06:16:30Z The Effect of Process Variables on Microstructure in Laser-Deposited Materials Bontha, Srikanth Laser Deposition Ti-6Al-4V Microstructure Rosenthal Solution Solidification Map Finite Element Modeling Transient Effects Distributed Heat Source The ability to predict and control microstructure in laser deposition processes requires an understanding of the thermal conditions at the onset of solidification. The focus of this work is the development of thermal process maps relating solidification cooling rate and thermal gradient (the key parameters controlling microstructure) to laser deposition process variables (laser power and velocity). The approach employs the well-known Rosenthal solution for a moving point heat source traversing an infinite substrate. Cooling rates and thermal gradients at the onset of solidification are numerically extracted from the Rosenthal solution throughout the depth of the melt pool, and dimensionless process maps are presented for both 2-D thin-wall and bulky 3-D geometries. Results for both small-scale (LENS) and large-scale (higher power) processes are plotted on solidification maps for predicting trends in grain morphology in laser-deposited Ti-6Al-4V. Although the Rosenthal predictions neglect the nonlinear effects of temperature-dependent properties and latent heat of transformation, a comparison with 2-D and 3-D nonlinear FEM results for both small-scale and large-scale processes suggests that they can provide reasonable estimates of trends in solidification microstructure. In particular, both the Rosenthal and FEM results suggest that changes in process variables could potentially result in a grading of the microstructure (both grain size and morphology) throughout the depth of the deposit and that the size-scale of the laser deposition process is important. In addition, the effects of a uniform distributed heat source on melt pool geometry and microstructure is investigated by superposition of the Rosenthal point source solution. In particular, the effect of beam width on melt pool length, melt pool depth, solidification cooling rates and thermal gradients is investigated. These results are also interpreted in the context of a solidification map to investigate the effect of beam width on trends in grain morphology in laser-deposited Ti-6Al-4V. Finally, transient effects near the free edge are investigated in both 2-D thin-wall and bulky 3-D geometries through thermal finite element analysis. Here the effect of transient melt pool behavior on solidification cooling rates and thermal gradients (and thereby the resulting microstructure) is investigated. 2006-12-07 English text Wright State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=wright1160133069 http://rave.ohiolink.edu/etdc/view?acc_num=wright1160133069 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection NDLTD
language English
sources NDLTD
topic Laser Deposition
Ti-6Al-4V
Microstructure
Rosenthal Solution
Solidification Map
Finite Element Modeling
Transient Effects
Distributed Heat Source
spellingShingle Laser Deposition
Ti-6Al-4V
Microstructure
Rosenthal Solution
Solidification Map
Finite Element Modeling
Transient Effects
Distributed Heat Source
Bontha, Srikanth
The Effect of Process Variables on Microstructure in Laser-Deposited Materials
author Bontha, Srikanth
author_facet Bontha, Srikanth
author_sort Bontha, Srikanth
title The Effect of Process Variables on Microstructure in Laser-Deposited Materials
title_short The Effect of Process Variables on Microstructure in Laser-Deposited Materials
title_full The Effect of Process Variables on Microstructure in Laser-Deposited Materials
title_fullStr The Effect of Process Variables on Microstructure in Laser-Deposited Materials
title_full_unstemmed The Effect of Process Variables on Microstructure in Laser-Deposited Materials
title_sort effect of process variables on microstructure in laser-deposited materials
publisher Wright State University / OhioLINK
publishDate 2006
url http://rave.ohiolink.edu/etdc/view?acc_num=wright1160133069
work_keys_str_mv AT bonthasrikanth theeffectofprocessvariablesonmicrostructureinlaserdepositedmaterials
AT bonthasrikanth effectofprocessvariablesonmicrostructureinlaserdepositedmaterials
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