A high-throughput methodology search for the optimum cooling rate in an advanced polycrystalline nickel base superalloy

Publication date: 15 August 2017
Source:Materials & Design, Volume 128
Author(s): Hongyu Wu, Jia Li, Feng Liu, Lan Huang, Xin Zeng, Qihong Fang, Zaiwang Huang, Liang Jiang
In powder metallurgy nickel base superalloy, the precipitation microstructure and mechanical properties are strongly dependent on the cooling rate. Thus, searching for the optimum cooling rate remains a critical research topic to maximize the mechanical performance. Previously, the "one sample, one experiment" approach is adopted for this optimization process, which is very costly and time-consuming. Here we demonstrate a high-throughput method to produce a gradient distribution of γ' precipitates within an individual specimen by introducing a wide range of cooling rates. The microscopic examinations show that the smallest average particle size of γ' phases corresponds to the fastest cooling rate, and vice versa. Unexpectedly, a two-stage distribution of Vickers hardness is observed, which is contradictive with the previous results and mechanistically explained by molecular dynamics (MD) simulation. Our results shed new insights on understanding the relationship between cooling rates and mechanical properties in polycrystalline nickel base superalloy.

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