Availableonlineatwww.sciencedirect.com SCIENCE DIRECT Acta materialia ELSEVIER Acta Materialia 54(2006)1289-1295 On the t-m martensitic transformation in Ce-Y-TZP ceramics Y L. Zhang ,X.J. Jin,YH Rong, T.Y. Hsu(Xu Zuyao),, D.Y.Jiang, J.L. Shi School of Materials Science and Engineering, Shanghai Jiao Tong Unicersity, Shanghai 200030, China Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China Available online 3 January 200Ker 2005 Received 14 October 2005: accepted 25 Octo Abstract The thermoelastic behavior and crystallography of the tetragonal(t)- monoclinic(m)martensitic transformation in Ce-Y-TZP ceramics are investigated by means of in situ transmission electron microscopy(TEM) and Wechsler-Lieberman-Read phenomenolog ical theory. In situ TEM observations show that in Ce-Y-TZP the t/m interface can move freely with the change of thermal stress sup- plied by the beam illumination, whereas this is not found in thermal cycles. Based on the features of reversibility of interface motion, large thermal hysteresis and high critical driving force for Ce-Y-TZP, the t-m transformation is suggested as a semi-thermoelastic one. The habit plane and the lattice correspondence are determined as(130) and [00 1J//[010]m, which is in agreement with the calci lated results of the phenomenological theory. c 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved Keywords: Martensitic phase transformation; Ceramics; TEM; Thermoelastic 1. Introduction knowledge, even the thermoelastic behavior of the trans formation has not been elucidated so far. i.e. is it a ther A variety of zirconia-containing ceramics were much moelastic transformation? investigated at the end of the last century after the claim Some authors suggested that the t-m martensitic of transformation toughening by Garvie in 1975 [1]. In transformation in zirconia-containing ceramics is a ther addition, the shape memory effect (SME) has been moelastic one [6-9, 12]. The evidence is summarized as observed in Mg-PSZ [2](partially stabilized zirconia), Ce- follows. (1)In Y2O3-ZrO2 [6], MgO-Zro2 [7] and MgO- TZP [3, 4](tetragonal zirconia polycrystalline), as well as Y2O3-ZrO2 [8,9] systems, in situ transmission electron in Ce-Y-TZP [4. Recently, it was revealed that &Ce- microscopy (TEM) studies have shown that the monoclinic under a recoverable strain or lete shape memory recovery laths induced by the electron beam could grow and retract d defo ating temperature(above 500C)[5]. This is the best SMe indicating a glissile t/m interface under thermal stresses among reported shape memory ceramics(SMCs) up to (2) In situ X-ray measurements were performed on a now. These properties are associated with the martensitic stressed surface in bulk Mg- PSZ [10, 11]. The materials transformation from tetragonal (t) to monoclinic(m) sym- had a background m phase content of approximately metry in such ceramics [3]. However, in comparison to its 13 vol % and the volume fraction was reversibly engineering applications, less attention has been paid to increased/decreased by 3 vol. during tensile loadi the mechanism of this unique transformation. To our unloading. Using an optical microscope with Nomarski interference. the reversible surface roughness was observed to appear/disappear on loading/unloading corresponding Eonmslpodeg: zutho r.Tel/fax:+862162932435 o the t-m transformation. Heuer et al. [ 12] concluded I@sjtu.edu.cn(T.Y.Hsu(XuZuyao)) that the t-m transformations in zirconia-containing 1359-6454$30.00 C 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved doi:l0.1016 factant2005.10.062On the t ! m martensitic transformation in Ce–Y-TZP ceramics Y.L. Zhang a , X.J. Jin a , Y.H. Rong a , T.Y. Hsu (Xu Zuyao) a,*, D.Y. Jiang b , J.L. Shi b a School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030, China b Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China Received 14 October 2005; accepted 25 October 2005 Available online 3 January 2006 Abstract The thermoelastic behavior and crystallography of the tetragonal (t) ! monoclinic (m) martensitic transformation in Ce–Y-TZP ceramics are investigated by means of in situ transmission electron microscopy (TEM) and Wechsler–Lieberman–Read phenomenolog￾ical theory. In situ TEM observations show that in Ce–Y-TZP the t/m interface can move freely with the change of thermal stress sup￾plied by the beam illumination, whereas this is not found in thermal cycles. Based on the features of reversibility of interface motion, large thermal hysteresis and high critical driving force for Ce–Y-TZP, the t ! m transformation is suggested as a semi-thermoelastic one. The habit plane and the lattice correspondence are determined as (1 3 0)t and [0 0 1]t//[0 1 0]m, which is in agreement with the calcu￾lated results of the phenomenological theory.
2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Martensitic phase transformation; Ceramics; TEM; Thermoelastic 1. Introduction A variety of zirconia-containing ceramics were much investigated at the end of the last century after the claim of transformation toughening by Garvie in 1975 [1]. In addition, the shape memory effect (SME) has been observed in Mg-PSZ [2] (partially stabilized zirconia), Ce￾TZP [3,4] (tetragonal zirconia polycrystalline), as well as in Ce–Y-TZP [4]. Recently, it was revealed that 8Ce– 0.50Y-TZP exhibits a complete shape memory recovery under a recoverable strain of 1.2% at a relatively high oper￾ating temperature (above 500 C) [5]. This is the best SME among reported shape memory ceramics (SMCs) up to now. These properties are associated with the martensitic transformation from tetragonal (t) to monoclinic (m) sym￾metry in such ceramics [3]. However, in comparison to its engineering applications, less attention has been paid to the mechanism of this unique transformation. To our knowledge, even the thermoelastic behavior of the trans￾formation has not been elucidated so far, i.e., is it a ther￾moelastic transformation? Some authors suggested that the t ! m martensitic transformation in zirconia-containing ceramics is a ther￾moelastic one [6–9,12]. The evidence is summarized as follows. (1) In Y2O3–ZrO2 [6], MgO–ZrO2 [7] and MgO– Y2O3–ZrO2 [8,9] systems, in situ transmission electron microscopy (TEM) studies have shown that the monoclinic laths induced by the electron beam could grow and retract following the same path when focusing and defocusing, indicating a glissile t/m interface under thermal stresses. (2) In situ X-ray measurements were performed on a stressed surface in bulk Mg-PSZ [10,11]. The materials had a background m phase content of approximately 13 vol.%, and the volume fraction was reversibly increased/decreased by
3 vol.% during tensile loading/ unloading. Using an optical microscope with Nomarski interference, the reversible surface roughness was observed to appear/disappear on loading/unloading corresponding to the t ! m transformation. Heuer et al. [12] concluded that the t ! m transformations in zirconia-containing 1359-6454/$30.00
2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.actamat.2005.10.062 * Corresponding author. Tel./fax: +86 21 62932435. E-mail address: zyxu@sjtu.edu.cn (T.Y. Hsu (Xu Zuyao)). www.actamat-journals.com Acta Materialia 54 (2006) 1289–1295