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Low cycle deformation behaviour of Zircaloy‐4 at elevated temperatures
Author(s) -
Bočarek M.,
AlvarezArmas I.,
Armas A. F.,
Petersen C.
Publication year - 1986
Publication title -
materialwissenschaft und werkstofftechnik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.285
H-Index - 38
eISSN - 1521-4052
pISSN - 0933-5137
DOI - 10.1002/mawe.19860170906
Subject(s) - creep , materials science , dislocation , saturation (graph theory) , deformation (meteorology) , stress (linguistics) , strain rate , metallurgy , compression (physics) , composite material , crystallography , analytical chemistry (journal) , chemistry , mathematics , linguistics , philosophy , combinatorics , chromatography
The LC deformation behaviour of Zry‐4 at 400°C and 600°C was examined by means of tension/compression experiments conducted in load and in strain control respectively. The main results were compared to those obtained at comparable conditions on the stainless steel type AISI 304. For both the materials the influence of the stress ratio R = σ min /σ max (where within one test σ max > 0 was kept constant) upon the lifetime T f at low and high homologeous temperature T h was examined. Whereas at the lower T h for R < 0 the lifetime decreased with decreasing R, the opposite was true at the higher T h . The explanation of the influence of R upon t f suggests that at high temperatures the fatigue damage rate Å f drops below the rate for creep damage Å c Two cases are considered. If the above damage mechanisms are sequentially independent the resulting damage rate Å ≈ Å c and hence Å c is the failure (rate) determining mechanism. In the case that the mechanisms are sequentially dependent then Å ≈ Å f . TEM investigations conducted on Zry‐4 cycled at 600° C have shown that the typical dislocation pattern revealed is a band structure consisting of dense dislocation walls separating denuded zones. The habit and the crystallographic characteristics of the band structure resemble the structure associated with PSBs observed in fee metals. The comparison of the values of the saturation stress τ s and the wall spacing d for different fee and hep metals shows that there is a proportionality between τ s and 1/d which is independent of stress and temperature.