Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报(英文版)

Transactions of Nonferrous Metals Society of China

Vol. 24    No. 1    July 2014

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Microstructure transition from stable tometastable eutectic growth in Ni-25%Al alloy
Zhong-ping QUE1, Ji-Ho GU1, Jong-Ho SHIN2, Je-Hyun LEE1

1. Department of Nano and Advanced Materials Engineering, Changwon National University,
Changwon, Gyeongnam 641-773, Korea;
2. Doosan Heavy Industries & Construction Co. Ltd., Changwon, Gyeongnam 642-792, Korea

Abstract:The microstructural evolution during directional solidification of the Ni-25%Al (mole fraction) alloy was investigated in the range of growth velocity from 10 to 100 μm/s under a given thermal gradient of 10 K/mm. The solidification microstructures reveal a transition from γ''''-β equilibrium eutectic to γ-β metastable eutectic plus β dendrites. A mixed microstructure of γ''''-β and γ-β eutectics produced at a growth velocity of 25 μm/s illustrates that the transition occurs during the competitive growth between γ and γ'''' phases. The growth temperature for each phase was considered to understand the microstructure selection during solidification. The experimental results show that a phase or a microstructure solidifying with the highest temperature under a given growth condition is preferentially selected upon solidification. In addition, both stable eutectic and metastable eutectic are shown to coexist and simultaneously grow in the velocity range between 25 and 60 μm/s due to their similar growth temperatures.

 

Key words: Ni-Al alloys; directional solidification; intermetallic compound; undercooling; eutectic; growth velocity; microstructure

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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