Speaker
Description
The understanding of columnar dendrite growth is essential for microstructure modelling. In additive manufacturing, direct measurement of the growth velocity or undercooling is difficult. To use the undercooling and growth velocity as a tool to control the microstructure, thermal modelling with growth kinetics is meaningful.
The classic approximate dendrite growth model based on the Ivantsov solution have been widely used with the macroscopic thermal calculation. This combination allows calculation of undercooling at the part-scale. For additive manufacturing new considerations are required due to the very high growth velocity and temperature gradient, which leads to the objective of this paper: finding the right model to predict undercooling and growth rate in the additive manufacturing process.
Approximate growth models were compared with results from phase field simulations for a binary Ni-Nb system. The comparison shows that the LGK model agrees well in both dendrite growth rate and tip radius with the phase field results, therefore could be used for the additive manufacturing modelling. For more realistic multi-components system, a pragmatic approach by extracting the functional relationship between dendrite growth velocity, tip radius and undercooling from phase field simulations and combining it with macroscopic model is proposed. A demonstration calculation with the truncated Scheil model introduced by Flood and Hunt is carried out for a single Laser Powder Bed Fusion (LPBF) process. Simulations of remelting and solidification in a single track scan require a short calculation time, while the results give the dendrite tip velocity and undercooling in addition to the temperature gradient and melting pool geometry by means of a classic thermal analysis.
| Speaker Country | Germany |
|---|