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Title: Effect of γ forming element additions on the homogenization behavior and formation of hierarchical microstructures in Ni-based superalloys
Here, we study the homogenization behavior and microstructure of seven Ni-Al-Ti alloys with quaternary additions of γ forming elements 4Cr, 4Co, 4Ru, 4Mo, 4Hf, 4 W and 2Re. To design a homogenization treatment, the as-cast microstructure is analyzed revealing the diffusion distances x between dendrite cores and interdendritic regions. The temperatures for homogenization are determined using differential scanning calorimetry (DSC) and Thermo-Calc simulations, to be between 1150 and 1275 °C. The time to achieve homogenization is modelled based on the residual segregation index δ utilizing diffusion distance, homogenization temperature and diffusion data. Electron probe micro analyzer (EPMA) measurements show that our predictions match for the 4Cr, 4Co, 4Ru, 4 W and 2Re alloys while the 4Hf alloy shows insufficient homogenization. Transmission electron microscopy (TEM) reveals a two-phase γ/γ’ microstructure after 750 °C / 24 h, whereby the 4Co and 4Ru alloys form hierarchical microstructures. We observe γ plates in the 4Co alloy and γ spheres in the 4Ru alloy. Ru in the 4Ru alloy is involved in stabilizing the morphology of γ spheres. We provide a straightforward method for the design of homogenization treatments of Ni-based superalloys and demonstrate an alloy design pathway for tailoring the phase stability of hierarchical microstructures.  more » « less
Award ID(s):
2105364
NSF-PAR ID:
10529102
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ;
Publisher / Repository:
Sciencedirect
Date Published:
Journal Name:
Journal of Alloys and Compounds
Volume:
975
Issue:
C
ISSN:
0925-8388
Page Range / eLocation ID:
172929
Subject(s) / Keyword(s):
Segregation Diffusion Superalloy Homogenization Hierarchical microstructure
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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