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Indexed by:Journal Papers

Date of Publication:2019-10-15

Journal:JOURNAL OF MOLECULAR LIQUIDS

Included Journals:EI、SCIE

Volume:292

ISSN No.:0167-7322

Key Words:Cu-Pb-Sn alloy; Network; Rod-like; Phase-field calculation; Solidification; Morphology evolution

Abstract:In the present study, hypomonotectic Cu-Pb-Sn alloys with Pb-rich secondary phase particles (SPPs) in different morphology were prepared at specific casting temperature (T-q) corresponding to different molar fraction (f(S0)) of the existing primary alpha-Cu (S-0) before pouring. The results show that the SPPs transform from continuously network to independently rod-like morphology and then become abnormally coarsening with increasing T-q. Phase field calculation was carried out to discuss the morphology evolution mechanism of the secondary phase droplets (L-2), which can effectively overcome the experimental difficulty of the investigation about the monotectic reaction with an extremely high reaction rate. It is found that f(s0) can strongly affect such morphology evolution. A relatively high f(s0) corresponding to a lower T-q is proven to promote the formation of network L-2. In contrast, a lower f(s0) corresponding to a higher T-q can promote the formation of rod-like L-2, which is mainly benefitted from the immiscibility of the Cu-rich residual liquid (L-1) and L-2. However, if T-q continuously increases, abnormally coarsening of L-2 will occur mainly through collision and coagulation driven by the Marangoni force and the solidification front's pushing. The coarsening process of L-2 during heating was observed through synchrotron radiation. This work reveals the morphology evolution mechanism of the SPPs in hypomonotectic Cu-Pb-Sn alloy during the monotectic reaction. (C) 2019 Elsevier B.V. All rights reserved.