Speaker
Description
Many industries depend on products formed at interfaces between liquids and solids, in other words during a wetting process. Due to the complexity of the wetting process especially for a highly reactive wetting system like liquid Aluminum (Al)/solid Nickel (Ni) at high temperatures, lab experimental study on the nucleation and growth of intermetallics is still limited.
Nanoscale simulations can be regarded as a potential option to unravel the mechanisms of intermetallic formation during the wetting of Al(l) on Ni(s).
Molecular Dynamics simulations were therefore performed with the Embedded Atom Method force field developed by Zhou et al. (2004). To simulate the spreading process, a droplet of Al(l) is brought in contact with a substrate of Ni(s) at 1023.15 K.
According to the Al-Ni phase diagram, the reactions between Al and Ni result in the formation of various intermetallics such as Al3Ni, Al3Ni2, NiAl, Al3Ni5, and Ni3Al depending on the temperature and atomic percentage. The structure of each intermetallic compound was studied individually. During the spreading time, formed compound’s structures in the present simulation were compared with reference marker of intermetallics (e.g. atomic percentage and coordination number) to detect the type of intermetallic (if any) of the reaction products.
The nucleation and growth of intermetallics, along and normal to the Ni surface, were studied in two different regimes: 1) Spreading regime when the contact angle relaxes 2) Quasi-equilibrium regime when the contact angle has almost reached its final value. The intermetallic lateral growth stops at the end of the spreading regime while the intermetallics normal growth continues during the quasi-equilibrium regime as well.
At the beginning of the wetting process, Al richer intermetallics formed but gradually transformed into Ni richer intermetallics. At the end, Al3Ni5 and AlNi3 were the dominant intermetallics in the substrate while AlNi was found in the droplet.
| Speaker Country | Belgium |
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