Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/36145
Title: Discontinuous yielding in Ni-base superalloys during high-speed deformation
Authors: Zhao, ZL
Ning, YQ
Guo, HZ
Yao, ZK
Fu, MW 
Keywords: Discontinuous yielding
Hardening
Softening
Dynamic recrystallization
Ni-base superalloys
Issue Date: 2015
Publisher: Elsevier
Source: Materials science & engineering. A, structural materials : properties, microstructure and processings, 2015, v. 620, p. 383-389 How to cite?
Journal: Materials science & engineering. A, structural materials : properties, microstructure and processing 
Abstract: Discontinuous yielding in Ni-base superalloy during high-speed compression has been investigated. Flow stress curves of GH4049 can be divided into two types: the first type curves display common flow behavior revealing work hardening, stable, softening and steady stages; the second type curves present abnormal flow behavior revealing discontinuous yielding feature, which were characterized by a sharp peak stress (sigma(p)), obvious upper yield point (sigma(u)) and a lower yield point. Apparent activation energies for peak values and upper values were calculated to be Q(P) = 1162 kJ mol(-1) and Q(U) = 1106 kJ mol(-1), respectively. Constitutive equations represent peak stress and upper stress as functions of strain rate and deformation temperature are described. First type curves present common work hardening behavior; however, second type curves present spiral hardening behavior since discontinuous softening during high-speed deformation. When GH4049 superalloys present first type flow behavior, volume fraction of dynamic recrystallization (X-DRX) can be described in terms of normal S-curves revealing slow-rapid-slow property. However, when alloys present second type flow behavior, X-DRX can be described in terms of double S-curves exhibiting sudden-steady-rapid-slow property.
URI: http://hdl.handle.net/10397/36145
ISSN: 0921-5093
DOI: 10.1016/j.msea.2014.10.041
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