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Lambers H.-G.,Lehrstuhl fur Werkstoffkunde Materials Science | Gorny B.,Lehrstuhl fur Werkstoffkunde Materials Science | Tschumak S.,Lehrstuhl fur Werkstoffkunde Materials Science | Maier H.J.,Lehrstuhl fur Werkstoffkunde Materials Science | Canadinc D.,Koc University
Procedia Engineering | Year: 2010

The crack growth behavior of low-alloy bainitic 51CrV4 steel was investigated. The current results indicate that the stress state present during the isothermal bainitic transformation has a strong influence on the crack propagation behavior in the near threshold regime, when the crack growth direction is perpendicular to the loading axis of the original sample undergoing phase transformation. However, the influence of stresses superimposed during the bainitic transformation on the crack growth behavior vanishes when the stress ratio is reduced from R=0.5 to R=0.1. Microstructural investigations revealed a locally pinned crack, indicating that the crack growth behavior in the near threshold regime is also strongly dependent on the local microstructure. Overall, the current results constitute the first step towards establishing a database for understanding and modeling the crack growth behavior in final work pieces exhibiting functionally-graded microstructures. © 2010 Published by Elsevier Ltd.

Lambers H.-G.,Lehrstuhl fur Werkstoffkunde Materials Science | Canadinc D.,Koc University | Maier H.J.,Lehrstuhl fur Werkstoffkunde Materials Science
Materials Science and Engineering A | Year: 2012

The current paper presents a thorough experimental analysis of the austenite-to-bainite phase transformation, and provides insight into microstructural changes associated with the observed transformation plasticity (TP). Specifically, the evolution of TP was studied in the presence of several parameters, namely pre-deformation, temperature and superimposed constant stresses, and the observed phenomena were linked to microstructural changes under these circumstances based on experimental data. One major finding is that the evolution of TP strains is governed both by the superimposed external stresses and the temperature dependence of internal stresses introduced by pre-deformation. © 2012 Elsevier B.V.

Lambers H.-G.,Lehrstuhl fur Werkstoffkunde Materials Science | Rusing C.J.,Lehrstuhl fur Werkstoffkunde Materials Science | Niendorf T.,Lehrstuhl fur Werkstoffkunde Materials Science | Geissler D.,Leibniz Institute for Solid State and Materials Research | And 4 more authors.
International Journal of Fatigue | Year: 2012

The low-cycle fatigue behavior of a high manganese austenitic alloy showing TWIP (Twinning-Induced Plasticity) in its homogenized as-received (AsRec) and in pre-strained conditions was determined. Pre-strains were applied both in tension and compression. The fatigue experiments, conducted in total strain control under fully reversed push-pull loading, were accompanied by thorough microstructural investigations utilizing electron backscatter diffraction and transmission electron microscopy. The results clearly lay out the different microstructural evolutions during cyclic loading of the AsRec and the pre-deformed conditions. Cyclic hardening prevails for the AsRec condition due to the increase in dislocation density and the subsequent rearrangement of dislocations into labyrinth and cell structures upon further cycling, whereas pronounced softening accompanied by a decrease in absolute value of mean stress dominated the cyclic deformation response of the pre-deformed conditions. © 2012 Elsevier Ltd. All rights reserved.

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