Phase Selection in Sub-Rapidly Solidified Au-20Sn Alloys

Abstract:

The sub-rapidly solidified Au-20Sn eutectic alloys were prepared by four different solidification pathways, such as, graphite mold conventional casting, graphite mold injection casting, copper mold injection casting, and water-cooled copper mold suction casting. The precipitating sequences of competing primary phases of sub-rapidly solidified Au-20Sn alloys with four different cooling rates were investigated. The results show that phase selection process is related to the cooling rates during sub-rapid solidification process. The primary ζ'-Au₅Sn phase with developed dendrites precipitate at low cooling rate (2.4×10−4.2×10² K/min) and the morphologies of the primary ζ'-Au₅Sn change to rosette-like at higher cooling rate (9.0×10³ K/min). While the cooling rate reaches to 3.5×10⁴ K/min, the primary ζ'-Au₅Sn phase can be suppressed but δ-AuSn phase will precipitate prior to the ζ'-Au₅Sn phase. On the basis of the classical nucleation theory and transient nucleation theory, the process of competitive nucleation between the ζ'-Au₅Sn phase and the δ-AuSn phase were analyzed for sub-rapid solidified Au-20Sn alloy. The theoretical calculations are consistent with the experimental investigations.

• Periodical: Materials Science Forum (Volume 817)
• Pages: 325-330
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.817.325
• Online since: April 2015
• Authors: Yu Hai Qu, Kai Jin Yang, Yan Tian Zhou, Yong Mao, Wei Zhang, Si Yong Xu
• Keywords: Au-20Sn Alloy, Phase Selection, Sub-Rapid Solidification

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