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The Effect of Heat Accumulation on the Local Grain Structure in Laser-Directed Energy Deposition of Aluminium

journal contribution
posted on 2023-02-14, 03:40 authored by C Hagenlocher, P O’Toole, Wei XuWei Xu, M Brandt, M Easton, A Molotnikov
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.

History

Journal

Metals

Volume

12

Article number

ARTN 1601

ISSN

2075-4701

eISSN

2075-4701

Language

English

Publication classification

C1 Refereed article in a scholarly journal

Issue

10

Publisher

MDPI