The Effect of Heat Accumulation on the Local Grain Structure in Laser-Directed Energy Deposition of Aluminium
Open Access
- 25 September 2022
- Vol. 12 (10), 1601
- https://doi.org/10.3390/met12101601
Abstract
The energy used to melt the material at each layer during laser-directed energy deposition (L-DED) accumulates in the solidified layers upon layer deposition and leads to an increase in the temperature of the part with an increasing number of layers. This heat accumulation can lead to inhomogeneous solidification conditions, increasing residual stresses and potentially anisotropic mechanical properties due to columnar grain structures. In this work, infrared imaging is applied during the directed energy deposition process to capture the evolution of the temperature field in high spatial and temporal evolutions. Image processing algorithms determined the solidification rate and the temperature gradient in the spatial and temporal evolutions and evidenced their change with the proceeding deposition process. Metallographic analysis proves that these changes significantly affect the local grain structure of the L-DED fabricated parts. The study provides comprehensive quantitative measurements of the change in the solidification variables in local and temporal resolutions. The comprehensive comparison of different parameter combinations reveals that applied power, and especially the frequency of the consecutive deposition of the individual layers, are the key parameters to adjusting heat accumulation. These findings provide a methodology for optimising L-DED manufacturing processes and tailoring the local microstructure development by controlling heat accumulation.Keywords
Funding Information
- Alexander von Humboldt Foundation (Feodor-Lynen-Scholarship)
This publication has 34 references indexed in Scilit:
- Formation of equiaxed crystal structures in directionally solidified Al-Si alloys using Nb-based heterogeneous nucleiScientific Reports, 2016
- An overview of Direct Laser Deposition for additive manufacturing; Part II: Mechanical behavior, process parameter optimization and controlAdditive Manufacturing, 2015
- An overview of Direct Laser Deposition for additive manufacturing; Part I: Transport phenomena, modeling and diagnosticsAdditive Manufacturing, 2015
- Understanding grain refinement in aluminium weldingWelding in the World, 2015
- Grain morphology evolution behavior of titanium alloy components during laser melting deposition additive manufacturingJournal of Alloys and Compounds, 2015
- Effect of inter-layer dwell time on distortion and residual stress in additive manufacturing of titanium and nickel alloysJournal of the American Academy of Dermatology, 2015
- Emissivity characteristics of roughened aluminum alloy surfaces and assessment of multispectral radiation thermometry (MRT) emissivity modelsInternational Journal of Heat and Mass Transfer, 2004
- The Hall–Petch relation in aluminium and its dependence on the grain boundary structurePhilosophical Magazine A, 1986
- Heat treating and melting material with a scanning laser or electron beamJournal of Applied Physics, 1977
- The effect of grain size and deformation sub-structure on mechanical properties of polycrystalline aluminumActa Metallurgica, 1973