Deformation-induced phase transformation in a Co-Cr-W-Mo alloy studied by high-energy X-ray diffraction during in-situ compression tests

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@article{1b9e1e1d4aca4e368149984bb785ca12,
title = "Deformation-induced phase transformation in a Co-Cr-W-Mo alloy studied by high-energy X-ray diffraction during in-situ compression tests",
abstract = "Nickel-free Co-Cr-W-Mo alloys exhibit a very low or even negative stacking fault energy, and therefore a pronounced tendency towards a deformation-induced phase transformation of the metastable face-centered cubic (fcc) γ-phase to the hexagonal close-packed (hcp) low-temperature ε-phase. In order to analyze the phase transformation in-situ and to correlate it to an external strain, compression tests between 30 °C and 400 °C were performed in a deformation dilatometer simultaneously to high-energy X-ray diffraction. Hence, the elastic strains of the fcc unit cell during compression, the external loads for the onset of the phase transformation and the temperature-dependency could be determined. In the parent fcc γ-phase, the evolution of an 101 fiber texture as well as texture inheritance effects and a distinct variant selection could be observed. Further, for the investigated alloy composition it is demonstrated that the continuum concepts of i) a structural stretch tensor and ii) an invariant plane strain perfectly agree with the widely-accepted nucleation theory of ε-martensite formation in Co-Cr alloys via Shockley partial dislocations on every second {111} γ plane. Both, the observed transformation texture as well as crystallographic transformation strains reveal the importance of shear stresses in this system. ",
author = "Irmgard Wei{\ss}ensteiner and Manuel Petersmann and Petra Erdely and Andreas Stark and Thomas Antretter and Helmut Clemens and Verena Maier-Kiener",
year = "2019",
month = feb,
doi = "10.1016/j.actamat.2018.10.035",
language = "English",
volume = "164.2019",
pages = "272--282",
journal = "Acta materialia",
issn = "1359-6454",
publisher = "Elsevier",
number = "February",

}

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TY - JOUR

T1 - Deformation-induced phase transformation in a Co-Cr-W-Mo alloy studied by high-energy X-ray diffraction during in-situ compression tests

AU - Weißensteiner, Irmgard

AU - Petersmann, Manuel

AU - Erdely, Petra

AU - Stark, Andreas

AU - Antretter, Thomas

AU - Clemens, Helmut

AU - Maier-Kiener, Verena

PY - 2019/2

Y1 - 2019/2

N2 - Nickel-free Co-Cr-W-Mo alloys exhibit a very low or even negative stacking fault energy, and therefore a pronounced tendency towards a deformation-induced phase transformation of the metastable face-centered cubic (fcc) γ-phase to the hexagonal close-packed (hcp) low-temperature ε-phase. In order to analyze the phase transformation in-situ and to correlate it to an external strain, compression tests between 30 °C and 400 °C were performed in a deformation dilatometer simultaneously to high-energy X-ray diffraction. Hence, the elastic strains of the fcc unit cell during compression, the external loads for the onset of the phase transformation and the temperature-dependency could be determined. In the parent fcc γ-phase, the evolution of an 101 fiber texture as well as texture inheritance effects and a distinct variant selection could be observed. Further, for the investigated alloy composition it is demonstrated that the continuum concepts of i) a structural stretch tensor and ii) an invariant plane strain perfectly agree with the widely-accepted nucleation theory of ε-martensite formation in Co-Cr alloys via Shockley partial dislocations on every second {111} γ plane. Both, the observed transformation texture as well as crystallographic transformation strains reveal the importance of shear stresses in this system.

AB - Nickel-free Co-Cr-W-Mo alloys exhibit a very low or even negative stacking fault energy, and therefore a pronounced tendency towards a deformation-induced phase transformation of the metastable face-centered cubic (fcc) γ-phase to the hexagonal close-packed (hcp) low-temperature ε-phase. In order to analyze the phase transformation in-situ and to correlate it to an external strain, compression tests between 30 °C and 400 °C were performed in a deformation dilatometer simultaneously to high-energy X-ray diffraction. Hence, the elastic strains of the fcc unit cell during compression, the external loads for the onset of the phase transformation and the temperature-dependency could be determined. In the parent fcc γ-phase, the evolution of an 101 fiber texture as well as texture inheritance effects and a distinct variant selection could be observed. Further, for the investigated alloy composition it is demonstrated that the continuum concepts of i) a structural stretch tensor and ii) an invariant plane strain perfectly agree with the widely-accepted nucleation theory of ε-martensite formation in Co-Cr alloys via Shockley partial dislocations on every second {111} γ plane. Both, the observed transformation texture as well as crystallographic transformation strains reveal the importance of shear stresses in this system.

UR - http://www.scopus.com/inward/record.url?scp=85055900993&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2018.10.035

DO - 10.1016/j.actamat.2018.10.035

M3 - Article

VL - 164.2019

SP - 272

EP - 282

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - February

ER -