Simulating microstructure formation in PBF-LB/M, Part 7, Fraunhofer IWM, Bastien Dietemann
Part 7: Simulating microstructure formation in PBF-LB/M
Dr. Bastien Dietemann, Fraunhofer IWM
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The formation of the microstructure grains depends on the temperature history that the material experiences during both melting and re-solidification.
But exactly how does this manifest itself?
In regions with a sufficiently high temperature, the melt pool is in a liquid state.
Over time, the thermal energy introduced by the laser is distributed through the part, forming a temperature gradient.
Once the temperature decreases below a certain value – the so called liquidus temperature – small grains start to grow from the melt.
The growth kinetics and growth direction of the grains depend on the local temperature.
The grains grow as long as the temperature is in a suitable range or until they come into contact with other grains that hinder further growth.
The entirety of all grains, including their sizes, shapes and orientations is what we call microstructure.
The simulation method that we use for this process is a cellular automaton. This method uses a mesh to discretize (dis-creet-eyes) the space and map the temperature data onto the mesh. The growth kinetics of the grains is then computed with the help of analytical models.
The result of this simulation is the final microstructure. An example of such a simulated microstructure might look like this.