Enhanced nucleation and refinement of eutectic Si by high number-density nano-particles in Al–10Si–0.5Sb alloys

Publication date: 5 March 2017
Source:Materials & Design, Volume 117
Author(s): Fengxiang Guo, Wei Wang, Wenhui Yu, Yong Zhang, Shaopeng Pan, Zhonghai Zhou, Dan Liu, Jingyu Qin, Yao Wang, Xuelei Tian
The mechanism of refinement of eutectic Si with Sb additions in an Al–10wt.% Si alloy is studied. The increased holding time designates a transition of the eutectic nucleation temperature from a decreased value to an increased one, accompanied by a morphological transformation of eutectic Si from lamellar to a shorter, rod-like shape. By ab initio molecular dynamics simulation, the chemical short-range order of −0.002 demonstrates weak affinity in the Al–Sb pair, which does not favor the existence of AlSb clusters in the melts. Sb–Sb segregation and the Sb–Si repulsive force are revealed, which promote the formation of Al-enriched precursors and the accumulation of Si atoms adjacent to precursors, inducing precursor nucleation. Continuous attachment of precursors and individual Si atoms during Si growth results in the high number-density nano-particles and suppresses the formation of twin grains within eutectic Si.

Graphical abstract

http://ift.tt/2j7r2r3