Journal of Materials Processing Technology 209 (2009) 5271–5275 Contents lists available at ScienceDirect Journal of Materials Processing Technology journal homepage: www.elsevier.com/locate/jmatprotec Mechanical properties of MgO–Al 2 O 3 –SiO 2 glass-infiltrated Al 2 O 3 –ZrO 2 composite A. Balakrishnan a,b , B.B. Panigrahi b , K.P. Sanosh a,b , Min-Cheol Chu b , T.N. Kim a , Seong-Jai Cho b,∗ a Department of Information and Electronic Materials Engineering, Paichai University, Daejeon 302-735, Republic of Korea b Division of Advanced Technology, Korea Research Institute of Standards & Science, Daejeon 305-340, Republic of Korea article info Article history: Received 5 September 2008 Received in revised form 8 March 2009 Accepted 22 March 2009 Keywords: ZTA Glass Infiltration Thermal expansion Compressive stress abstract This work attempts to improve the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabi- lized) composite by infiltrating a glass (magnesium aluminum silicate glass) of lower thermal expansion on the surface at high temperature. The glass improved the strength of the composite at room tempera- ture as well as at higher temperatures. There was a significant improvement in the Weibull modulus after the glass infiltration. Glass-infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the infiltrated glass. © 2009 Elsevier B.V. All rights reserved. 1. Introduction The strengthening of polycrystalline ceramic has been a topic of interest among the ceramists over the past few decades. Whiskers (or particles) reinforcing, phase transformation and surface residual compression methods have been shown to improve the mechanical properties of ceramics (Lange, 1982; Lin et al., 1993; Virkar, 1987; Virkar et al., 1987). The interest in the surface compression method lies for two reasons: firstly, the residual stress provides balancing force against the external stress (loading) and secondly, it leads to the crack closure (ASM International, 1991; Wulf and Rombach, 1999) which enhances the service behavior of the parts. Various techniques are applied for inducing surface compression such as, quenching treatments (Kirchner et al., 1971), coating of a lower expansion materials (Kirchner, 1979), phase transformation (to a larger volume phase) (Swain et al., 1980), ion exchange technique (Lin and Virkar, 2001), chemical strengthening (surface coating by chemical reaction (Kirchner et al., 1968; Marple and Green, 1988), grinding (Kishino et al., 1996), grid blasting (Chakraverty and Rice, 1997) and shot peening techniques (Wulf and Tobias, 2006), etc. However, the above methods show some disadvantages also. The machining, grinding, grid blasting and shot peening procedures affect the precision, surface finish and can initiate surface flaws (Wulf and Tobias, 2002). Moreover, creating a compressive stress ∗ Corresponding author. Tel.: +82 42 868 5388. E-mail addresses: sjcho@kriss.re.kr, the krecian@yahoo.com (S.-J. Cho). at the depth of strength controlling flaws (typically on the order of ∼200 m) is difficult by above techniques. Recently, a more effec- tive glass infiltration method (Balakrishnan et al., 2007; Chu et al., 2007; Guazzato et al., 2005; Hua et al., 2003; Xiang et al., 2004) has been reported which can produce compressive stress in the layers much deeper than the depth of the strength controlling flaws and can enhance the strength of ceramics by about 25–50%. Alumina–zirconia composite has attracted a lot of interest because of its excellent toughness and strength (Magdalena and Marek, 2006). The increase in the strength and toughness of this composite is attributed to the transformation toughening mecha- nism. If the properties of such material could be enhanced, it would add a further value to the service and performance of its compo- nent. The previous works (Balakrishnan et al., 2007; Guazzato et al., 2005; Hua et al., 2003; Xiang et al., 2004) have shown to strengthen the alumina–zirconia composite by the glass infiltration technique. However, many of the issues related to the strengthening (by glass treatment) have not yet been fully studied; such as quantification of surface stress and the effect of thermal and elastic properties mis- match on the stress, high temperature properties, thermal shock resistance, etc. In the present investigation, efforts have been made to understand the strengthening behavior of zirconia-toughened alumina (ZTA) by using a magnesium aluminum silicate (MAS) glass, having relatively lower thermal expansion compared to the thermal expansion of ZTA. The high temperature flexural strength and the thermal shock resistant properties have also been evalu- ated. The surface stresses generated during glass infiltration have been characterized experimentally as well as theoretically. 0924-0136/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2009.03.014