Thermal and mechanical stability of retained austenite surrounded by martensite with different degrees of tempering
TLDR
In this paper, the effect of tempering in martensite is isolated from other factors influencing the stability of austenite, and the thermal stability during heating of retained Austenite was evaluated by monitoring phase fractions as a function of controlled temperature employing both dilatometry and magnetometry measurements.Abstract:
The mechanical and thermal stability of austenite in multiphase advanced high strength steels are influenced by the surrounding microstructure. The mechanisms underlying and the relations between thermal and mechanical stability are still dubious due to the difficulty of isolating other factors influencing austenite stability. In this work, martensite/austenite microstructures were created with the only significant difference being the degree of tempering of the martensite matrix. Hence, the effect of tempering in martensite is isolated from other factors influencing the stability of austenite. The thermal stability during heating of retained austenite was evaluated by monitoring phase fractions as a function of controlled temperature employing both dilatometry and magnetometry measurements. The mechanical stability was studied by performing interrupted tensile tests and determining the remaining austenite fraction at different levels of strain. The thermal stability of this remaining austenite after interrupted tests was studied by subsequent reheating of strained specimens. The results are evidence for the first time that thermal recovery of martensite during reheating assists austenite decomposition through shrinkage and softening of martensite caused by a reduction of dislocation density and carbon content in solid solution. This softening of martensite also leads to a subsequent reduction of austenite mechanical stability. Additionally, remaining austenite after pre-straining at room temperature was thermally less stable than before pre-straining, demonstrating that plastic deformation has opposing effects on thermal and mechanical stability.read more
Citations
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Controlling the work hardening of martensite to increase the strength/ductility balance in quenched and partitioned steels
TL;DR: In this article, martensite properties were varied through heat treatment in a low carbon Q&P steel consisting of retained austenite and martensites and additional conditions were produced by reheating the steel to 450°C for 30min or to 700°C followed immediately by quenching.
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Correlation between microstructure and yield strength of as-quenched and Q&P steels with different carbon content (0.06–0.42 wt%C)
TL;DR: In this paper, both as-quenched and Q&P microstructures are simplified and regarded as a mixture of α′ phase (containing M1, M2 or BF) and γ phase (RA).
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Impact of intercritical annealing temperature and strain state on mechanical stability of retained austenite in medium Mn steel
TL;DR: In this paper, the effect of intercritical annealing temperature on retained austenite is studied using interrupted tests, and the mechanical stability of retained Austenite at uniaxial tension and plane strain states is further investigated, to understand the transformation of retainedAustenite.
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The influence of the austenite grain size on the microstructural development during quenching and partitioning processing of a low-carbon steel
TL;DR: In this article, the influence of the prior austenite grain size (PAGS) on the microstructural development of a low carbon steel during quenching and partitioning (Q&P) processing is investigated.
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Microstructure evolution and corrosion behavior of dissimilar 304/430 stainless steel welded joints
TL;DR: In this article, the phase evolution within each weld was analyzed using thermodynamics calculation and electron back-scattered diffraction (EBSD), and it was found that the welded joints were mainly composed of martensite and ferrite phases.
References
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Orientation gradients and geometrically necessary dislocations in ultrafine grained dual-phase steels studied by 2D and 3D EBSD
TL;DR: In this article, orientation gradients and geometrically necessary dislocations (GNDs) in two ultrafine grained dual-phase steels with different martensite particle size and volume fraction were analyzed using high-resolution electron backscatter diffraction (EBSD).
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An experimental investigation of extrapolation methods in the derivation of accurate unit-cell dimensions of crystals
J B Nelson,D P Riley +1 more
TL;DR: In this paper, it was shown that the absorption error in the apparent unit-cell dimension a is proportional to cos 2θ/sinθ + cos 2 θ/θ.
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The effect of morphology on the stability of retained austenite in a quenched and partitioned steel
TL;DR: In this paper, X-ray diffraction and transmission electron microscopy experiments are employed to investigate the mechanical stability of retained austenite in a quenching and partitioning steel.
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Thermal stability of retained austenite in TRIP steels studied by synchrotron X-ray diffraction during cooling
N.H. van Dijk,A.M. Butt,Lie Zhao,Jilt Sietsma,S.E. Offerman,Jonathan P. Wright,S. van der Zwaag +6 more
TL;DR: In this paper, the authors performed in situ X-ray diffraction measurements at a synchrotron source in order to study the thermal stability of the retained austenite phase in transformation induced plasticity steels during cooling from room temperature to 100 K.