Decades of academic research has gone into developing ultrafine eutectic and near-eutectic alloys of the systems Ti-Fe-Sn-Nb, Ti-Fe-Co, Fe-Ti-Si, Fe-Ti-Zr-B, etc., with remarkable mechanical properties. However, no conventional casting process exists that can provide high enough cooling rates necessary for growing such microstructures through the bulk without introducing considerable heterogeneities. This has left them unused and unpopular when it comes to industrial applications. Additive Manufacturing (AM), with its inherently high cooling rates, may be the ideal processing route for these alloys.
In this work, we studied alloy production and gas atomisation of two near-eutectic alloys, namely Fe82.4Ti17.6 and Ti66Fe27Nb3Sn4 (all at%), with the objective of producing high quality pre-alloyed powders for Laser Metal Deposition (LMD) and Selective Laser Melting (SLM) respectively. The powders produced by three different gas atomization techniques were studied and their microstructures were analysed based on the knowledge acquired from some rapid solidification studies (10 to 100
K/s) that have been carried out on similar alloys. The bulk microstructure (and thus, mechanical properties) was correlated to different compositions, cooling rates and casting methods. These studies have been transferred to the microstructural analysis of the alloyed powders produced by three different gas atomisation techniques.
Comparing powders of different sizes, formed by different solidification rates, further revealed the influence of particle size on microstructural features (like inter-lamellar spacing λ, eutectic morphology and phase distribution) and their evolution. These relationships affect the choice of particle size ranges, processing parameters and reusability during AM of these alloys. This ongoing study aims to improve our overall understanding of eutectic and near-eutectic microstructures in meta-stable equilibriums, while developing potentially excellent materials targeted at the automotive, aerospace and tools industries.
