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- Title
Understanding the Microstructure Formation of Ti-6Al-4V During Direct Laser Deposition via In-Situ Thermal Monitoring.
- Authors
Marshall, Garrett; Young, W.; Thompson, Scott; Shamsaei, Nima; Daniewicz, Steve; Shao, Shuai
- Abstract
Understanding the thermal phenomena associated with direct laser deposition (DLD) is an important step toward obtaining 'process-property-performance' relationships for various designed parts and materials, as well as achieving increased process control for meeting application constraints. In this study, a thermally monitored laser engineered net shaping (LENS™) system was used with time-invariant (uncontrolled) build parameters to construct Ti-6Al-4V cylinders. During fabrication, the part's thermal history and melt pool temperature were recorded via an in-chamber infrared camera and a dual-wavelength pyrometer, respectively. These tools demonstrate the use of non-destructive thermographic inspection for ensuring target part quality and/or microstructure. For the chosen part geometry, the melt pool was found to be approximately 40%-50% superheated during DLD, reaching temperatures as high as 2500°C. Temperature gradients varied and peaked around 1000°C/mm along the diameter of the relatively small cylinders. Cooling rates within the melt pool were found to increase as maximum melt pool temperature increased, for instance, from 12,000°C/s to 25,000°C/s. The post-DLD Ti-6Al-4V microstructure was found to vary from columnar near the substrate, or substrate-affected zone, to equiaxed approximately 2-3 mm from the substrate. Bulk heating of the part due to successive layer deposits was shown to promote α″ to an α + β decomposition, while prior- β grains were observed near and far from the substrate.
- Subjects
TITANIUM-aluminum-vanadium alloys; MICROSTRUCTURE; LASER deposition; THERMOGRAPHY; PYROMETERS; COOLING
- Publication
JOM: The Journal of The Minerals, Metals & Materials Society (TMS), 2016, Vol 68, Issue 3, p778
- ISSN
1047-4838
- Publication type
Article
- DOI
10.1007/s11837-015-1767-z