Amorphous solidification mechanism of multicomponent Ti-Cu based alloy investigated by molecular dynamics simulation and drop tube experiments
The amorphous solidification mechanism of liquid Ti41.5Cu37.5Ni7.5Hf5Sn5Zr2.5Si alloy was characterized by both the DeePMD simulation method and drop tube experiments.The MD calculation results revealed that a lower temperature increased the total coordination number of the first nearest neighbor atoms in liquid alloy,but reduced that of Ti atoms.The number of icosahedral and icosahedral-like clusters in the liquid alloy was also significantly increased with the temperature decreasing,whereas the proportion of central Ti atoms was obviously decreased.In the amorphous solidification process,Ti atoms exhibited weak affinity with large-sized atoms such as Zr,Cu and Hf,and also showed a weak ability of structuring icosahedral clusters.Under free-fall conditions,alloy droplet undercooling increased with reduced diameter,and its solidification microstructure mainly consisted of a little amount of Cu-rich phase,extremely fine irregular(Ti2Cu+TiCu)eutectic and amorphous phase.When the alloy droplet diameter decreased to 566 pm,an amorphous phase appeared in solidified microstructures which represented a critical undercooling of 312 K(0.27TL).As the droplet size continued to decrease,the volume fraction of the amorphous phase gradually increased.When the alloy droplet became smaller than 317 pm,the nucleation and growth of crystalline phases were suppressed,resulting in the realization of completely amorphous solidification.
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