Microstructure evolution of solution treatable AlSi10Mg Alloy during thermal treatment

What is it about?

The fast quenching involved in additive manufacturing, particularly for solution treatable alloys, produces an unique cellular structure. This paper describe the change of microstructure as function of anneal temperature. Results show the phase separation, Si dissolution, cellular structure collapsing, and microstructure ripening. These phenomena change the length scale and distribution of the precipitates and should have significant effect on mechanical properties (this article )and thermal properties (articles).

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Why is it important?

Cellular structure produced during the rapid solidification process creates an unique condition with phase separation (primary alpha aluminum and Si rich cellular wall) and a oversaturated primary aluminum. In addition, the small amount of additive such as Mg will be tied in the Si rich cellular wall. This microstructure evaluation of additive manufactured will be completely different than conventional solution treated, quenched AlSi10Mg alloy. This paper uniquely reports the dissolution of Si from primary alpha alumina and the formation of Si precipitates, instead of the formation of intermetallic beta phase which normally observed in solution treated, quenched alloy. Evidence indicates the change of lattice parameter during thermal anneal in the as-built part is due to Si dissolution, not because of residue stresses. Finally, the impact of evolution of microstructure on microhardness and elastic constant is reported. These phenomena should be common in solution treatable alloys used in additive manufacturing process.

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