Mughrabi H (2022)
Publication Type: Journal article
Publication year: 2022
Book Volume: 96
Pages Range: 546-551
Journal Issue: 6
In several experimental microstructure-based studies on steady-state deformation in high-temperature creep and, in particular, in cyclic deformation it has been observed that non-negligible microstructural changes persist after the macroscopic stress-strain response has become stationary. These microstructural changes are related primarily to a slight increase of the dislocation density, mainly in the form of geometrically necessary dislocations (GND) in the cell walls/subgrain boundaries. The latter are initially associated with only minor misorientations but then transform gradually into much sharper subgrain boundaries with higher misorientations. It is interesting to note that these continuing microstructural changes do not affect the flow stress significantly and therefore do not cause appreciable deviations from steady state. The following natural explanation is proposed: 1) The added GND do strengthen the material, but not as effectively as statistically stored dislocations would do. 2) As a consequence of the transition of the initial dislocation arrangement to one of lower internal stresses and lower energy, the "arrangement factor" in the Taylor flow-stress law is reduced a little. Thus, in the Taylor flow-stress law, the effects named above can be, to some extent, self-compensating, rendering the flow stress rather insensitive to subtle microstructural changes. The dependence of the flow stress on microstructural quantities such as the dislocation density and the cell/subgrain size can be described in good approximation by well-known semiempirical relationships and almost irrespective of the details and type of deformation not only for steady-state, but also for non-steady-state deformation. This suggests that the gross strength-governing features of the deformation-induced dislocation microstructure are rather similar in all cases discussed.
APA:
Mughrabi, H. (2022). Implications of non-negligible microstructural variations during steady-state deformation. International Journal of Materials Research, 96(6), 546-551. https://doi.org/10.3139/ijmr-2005-0098
MLA:
Mughrabi, Hael. "Implications of non-negligible microstructural variations during steady-state deformation." International Journal of Materials Research 96.6 (2022): 546-551.
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