Availableonlineatwww.sciencedirect.com SCIENCE Acta materialia ELSEVIER Acta Materialia 52(2004)5709-5721 Martensitic transformation in zirconia Part Il martensite wth Sylvain deville gerard Guenin, Jerome Chevalier Associate Research Unit 5510, Materials Science Department, National Institute of Applied Science(GEMPPM-INSA), Bat B Received 13 July 2004: received in revised form 23 August 2004: accepted 26 August 2004 Available online 25 September 2004 Abstract Though the martensitic transformation in zirconia has been the object of a very large number of studies for the last decades, qualitative and quantitative observations of the formation and growth of relief induced by low temperature treatments has hardly ever been reported. In the first part of the study(Martensitic transformation in zirconia, Part D), we have demonstrated the excellent agreement between the atomic force microscopy quantitative observations and the outputs of the calculations derived from the phe- nomenological theory of martensitic transformation. The intermediate stages of transformation were nonetheless not considered In this second part, the growth mechanisms of monoclinic phase resulting from the martensitic transformation in ceria-stabilized conia(10 mol% CeO2)are investigated. Surface transformation is induced by aging treatments in water vapor at 413 K. The obser- vations are rationalized by the recent analysis proposed for the crystallographic ABCl correspondence choice, where the c, axis transforms to the cm axis. Three growth modes are observed and interpreted in terms of transformation strains accommodation is the largest. The influence of grain boundary paths on the surface relief features is demonstrated. Overall, our results strong, stains Microcracks formation is observed, explaining grain pop-out where the crystallographic disorientation between two adjacent grains port the non-existence of a critical grain size for low temperature transformation, confirmed by the classical thermodynamics theory applied to this particular case. o 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Zirconia; Martensite transformation; Atomic force microscopy; Microcracks 1. Introduction phenomenon is know as aging, and has been widely investigated for its detrimental consequences on the long Martensitic transformations occur in a number of term performance of zirconia components. Several con metal alloys but also minerals and ceramics like zirconia clusions were drawn from the experimental observa- 2 ] In order to stabilize zirconia and retain it in its tions, performed mostly by tEm, sEM and XRD. metastable tetragonal structure at ambient temperature, among which the existence of a critical grain size was it is possible alloying it with various oxides, among observed, size varying from 0. 1 to 0.5 um in the case which yttria(Y2O3) and ceria(CeO2). If the metastable of 3Y-TZP [5, 6]. This existence of a critical grain size tetragonal structure is indeed retained at ambient tem- was demonstrated by the application of the classical perature, the transformation can however occur during thermodynamics theory [7, 8]. Moreover, it was argued low temperature treatment in water vapor [3, 4]. This the transformation was very different in the case ofY TZP and Ce-TZP, because of the respective trivalent Corresponding author. Tel: +334 7243 63 57; fax: +33 4 72 4385 and quadrivalent nature of the stabilizE ing specie, leading to a different oxygen vacancies concentration []. As a E-mail address: sylvain. deville(ainsa-lyon fr(S. Deville) consequence, the aging sensitivity of these two materials 1359-6454/$30.00 C 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi: 10. 1016/j.actamat. 2004.08.03Martensitic transformation in zirconia Part II. Martensite growth Sylvain Deville *, Ge´rard Gue´nin, Je´roˆme Chevalier Associate Research Unit 5510, Materials Science Department, National Institute of Applied Science (GEMPPM-INSA), Baˆt B. Pascal, 20 av. A. Einstein, 69621 Villeurbanne Cedex, France Received 13 July 2004; received in revised form 23 August 2004; accepted 26 August 2004 Available online 25 September 2004 Abstract Though the martensitic transformation in zirconia has been the object of a very large number of studies for the last decades, qualitative and quantitative observations of the formation and growth of relief induced by low temperature treatments has hardly ever been reported. In the first part of the study (Martensitic transformation in zirconia, Part I), we have demonstrated the excellent agreement between the atomic force microscopy quantitative observations and the outputs of the calculations derived from the phe￾nomenological theory of martensitic transformation. The intermediate stages of transformation were nonetheless not considered. In this second part, the growth mechanisms of monoclinic phase resulting from the martensitic transformation in ceria-stabilized zir￾conia (10 mol% CeO2) are investigated. Surface transformation is induced by aging treatments in water vapor at 413 K. The obser￾vations are rationalized by the recent analysis proposed for the crystallographic ABC1 correspondence choice, where the ct axis transforms to the cm axis. Three growth modes are observed and interpreted in terms of transformation strains accommodation. Microcracks formation is observed, explaining grain pop-out where the crystallographic disorientation between two adjacent grains is the largest. The influence of grain boundary paths on the surface relief features is demonstrated. Overall, our results strongly sup￾port the non-existence of a critical grain size for low temperature transformation, confirmed by the classical thermodynamics theory applied to this particular case.
2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Zirconia; Martensite transformation; Atomic force microscopy; Microcracks 1. Introduction Martensitic transformations occur in a number of metal alloys but also minerals and ceramics like zirconia [1,2]. In order to stabilize zirconia and retain it in its metastable tetragonal structure at ambient temperature, it is possible alloying it with various oxides, among which yttria (Y2O3) and ceria (CeO2). If the metastable tetragonal structure is indeed retained at ambient tem￾perature, the transformation can however occur during low temperature treatment in water vapor [3,4]. This phenomenon is know as aging, and has been widely investigated for its detrimental consequences on the long term performance of zirconia components. Several con￾clusions were drawn from the experimental observa￾tions, performed mostly by TEM, SEM and XRD, among which the existence of a critical grain size was observed, size varying from 0.1 to 0.5 lm in the case of 3Y–TZP [5,6]. This existence of a critical grain size was demonstrated by the application of the classical thermodynamics theory [7,8]. Moreover, it was argued the transformation was very different in the case of Y– TZP and Ce–TZP, because of the respective trivalent and quadrivalent nature of the stabilizing specie, leading to a different oxygen vacancies concentration [4]. As a consequence, the aging sensitivity of these two materials 1359-6454/$30.00
2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.actamat.2004.08.036 * Corresponding author. Tel.: +33 4 72 43 63 57; fax: +33 4 72 43 85 28. E-mail address: sylvain.deville@insa-lyon.fr (S. Deville). Acta Materialia 52 (2004) 5709–5721 www.actamat-journals.com