Experimental and molecular dynamics studies on the mechanism of twinning formation in Fe-Al-based alloys during rapid solidification

Twin structures are commonly found in many metals and play a significant role in determining the mechanical properties and corrosion resistance of alloys. However, it is very challenging to observe the formation of twins in melt using traditional methods. In this paper, Fe90Al10 alloy was obtained by the vacuum non-consumable arc-melting method, and the results showed that the grain misorientation in the rapidly solidified Fe90Al10 alloys do not always follow a Mackenzie distribution, there is a peak at 60°, and it is well-known that Σ3 twin boundaries have an misorientation difference of 60°, Therefore, another nucleation method exists at the Σ3 grain boundary. Subsequently, Molecular dynamics simulations of Fe90Al10 alloys have shown that twin formation is sporadic and occurs through heterogeneous nucleation on the surface of previously formed grains, and only Σ3 twin boundaries can be formed in this way, which becomes a way for BCC metals to form twins during solidification, this is also consistent with experimental results, in addition to random nucleation, heterogeneous nucleation also exists during the rapid solidification of Fe-Al ally. Additionally, the aggregation of icosahedral-like (ICO-like) structures present in the under cooled melt leads to the heterogeneous nucleation of twinning and the difference in volume between the twin crystals will affect the subsequent evolutionary process. Therefore, the experimental and simulation results in this study strongly explain a formation mechanism of twins in BCC metals during rapid solidification.