Pedrazzini, S., Pek, M.E., Ackerman, A.K. et al. (10 more authors) (Submitted: 2020) Influence of powder-bed temperature on the microstructure and mechanical properties of Ti-6Al-4V produced by selective laser melting. arXiv. (Submitted)
Abstract
Advanced characterisation techniques were used on LPBF Ti-6Al-4V samples produced on a heated base plate. When the substrate temperature is 100°C the elongation is 6\%, which increases and peaks at 10\% at 570°C, then sharply decreases to zero ductility at 770°C. At 100°C, a heavily strained and twinned microstructure, primarily composed of {\alpha}+{\alpha}', was observed and it was comparable to asbuilt microstructures obtained by conventional LPBF methods. At higher temperatures, twins are no longer present and instead nano-scale {\beta} precipitates are observed within {\alpha}' and {\alpha}, as well as dislocation networks (570°C) and tangles (770°C). Solute segregation at crystal defects was observed in all pre-heating conditions. Al and V segregation at microtwins was observed in the 100°C sample, reporting for the first time `selective' and mutually exclusive Al- and V-rich regions forming in adjacent twins. V segregation at dislocations was observed in the 570°C and 770°C samples, consistent with the higher preheating temperatures. High O contents were measured in all samples but with apparent opposing effects. At 100°C and 570°C was estimated to be below the critical threshold for O embrittlement and locally aids in maintaining a strength high by solid solution strengthening, whereas at 770°C it was above the threshold, therefore failing in a brittle fashion. Based on these observations, the initial increase in ductility from 100°C to 570°C is attributed to a reduction in microtwins and the dislocation networks acting as `soft barriers' for slip within a coarser microstructure. The lack of ductility at 770°C was attributed to local solute redistribution causing dislocation pinning and an increase of O content in this sample.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2020 The Author(s). For reuse permissions, please contact the Author(s). |
Keywords: | cond-mat.mtrl-sci; cond-mat.mtrl-sci |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Mechanical Engineering (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 24 Jun 2020 07:06 |
Last Modified: | 24 Jun 2020 09:05 |
Published Version: | https://arxiv.org/abs/2006.08288 |
Status: | Submitted |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:162376 |