CERAMICS INTERNATIONAL ELSEVIER Ceramics International 25(1999)395-408 Review: High temperature deformation of Al2O3-based ceramic particle or whisker composites Q. Tai*, A. Mocellin LSG2M, UMR 7584, Ecole des Mines, Parc de saurupt, F-54042 Nancy Cedex, france Received 6 September 1997; accepted 17 November 1997 Abstract The major theoretical models for creep and the creep rate equations of ceramic materials and their dispersed phase composites e briefly reviewed. Then the literature on high temperature deformation behaviours of Al2O3-based oxide ceramic particle com- osites(Al2O3-ZrO2, Al2O3-Y3Al5O12, Al2O3-Tio2) and Al2O3-based non-oxide ceramic particle or whisker composites(Al2O3- SiC(w), Al2O3-SiC(p). Al2O3-TiCx Ni-x)since the mid 1980s is reviewed. Most studies have been concerned with the Al2O3-ZrO2 and Al2O3-SiC systems. The influences of various factors on the creep behaviours, the changes of the microstructure in the deformed specimens and the creep mechanisms of these composites are summarised and analysed. c 1999 Elsevier Science Limited and Techna S.r. l. all rights reserved 1. Introduction and reliabilities. Great emphasis is placed on their high temperature creep behaviours. In recent years, structural ceramic materials have The purpose of this paper is to recall briefly the major attracted much attention, because of their excellent theoretical models for creep and then to review the mechanical properties such as high strength, hardness, available information on the plastic deformation beha- anti-abrasion, chemical stability and heat resistance. viours of Al2O3-based ceramic composites. Composites There has been a recognition of the potential of struc- reinforced by long fibres are not discussed here since tural ceramics for use both in high temperature appli- their fabrication procedures markedly differ from those cations in advanced heat engine and heat exchangers based on powder processing which yield materials with and in ambient temperature applications in cutting dispersed phases tools, and wear parts. The disadvantage of ceramics is their low fracture toughness and poor mechanical relia- bility which so far have limited their practical applica 2. Deformation mechanisms s. me o Improve toughness and retain their high-temperature creep 2. 1. The rate equations for plastic deformation properties as well as enhance their mechanical reliability are a major challenge. One way to achieve these goals is The high temperature creep of single phase crystalline through the development of composite structures. That materials may be expressed by a relationship of the fol is to the ceramic matrices are added dispersed ceramic lowing form: particles, whiskers or fibres which reinforce the matrices and improve their mechanical properties Alumina-based ceramic composites such as Al_O3- E=A Zr02, Al O3-Y3AlsO12, Al2O3-SiC, Al,O3-TiC, Al,O TiCNI-x composites are widely studied, as to their where E is the steady state creep rate, A is a dimension ambient and high temperature mechanical properties less constant, D is the appropriate diffusion coefficient, G is the shear modulus, b is the magnitude of the Bur esponding author at Nanjing University of Chemical Tech- gers vector, k is Boltzmanns constant, Tis the absolute nology, 210009, Nanjing, People's Republic of China. temperature, d is the grain size, o is the applied stress, 0272-8842/99/$20.00@ 1999 Elsevier Science Limited and Techna S.r. L. All rights reserved PII:S0272-8842(98)00017-0Review: High temperature deformation of Al2O3-based ceramic particle or whisker composites Q. Tai *, A. Mocellin LSG2M, UMR 7584, Ecole des Mines, Parc de Saurupt, F-54042 Nancy Cedex, France Received 6 September 1997; accepted 17 November 1997 Abstract The major theoretical models for creep and the creep rate equations of ceramic materials and their dispersed phase composites are brie¯y reviewed. Then the literature on high temperature deformation behaviours of Al2O3-based oxide ceramic particle com￾posites (Al2O3-ZrO2, Al2O3-Y3Al5O12, Al2O3-Tio2) and Al2O3-based non-oxide ceramic particle or whisker composites (Al2O3- SiC(w), Al2O3-SiC(p), Al2O3-TiCxN1-x) since the mid 1980s is reviewed. Most studies have been concerned with the Al2O3-ZrO2 and Al2O3-SiC systems. The in¯uences of various factors on the creep behaviours, the changes of the microstructure in the deformed specimens and the creep mechanisms of these composites are summarised and analysed. # 1999 Elsevier Science Limited and Techna S.r.l. All rights reserved. 1. Introduction In recent years, structural ceramic materials have attracted much attention, because of their excellent mechanical properties such as high strength, hardness, anti-abrasion, chemical stability and heat resistance. There has been a recognition of the potential of struc￾tural ceramics for use both in high temperature appli￾cations in advanced heat engine and heat exchangers and in ambient temperature applications in cutting tools, and wear parts. The disadvantage of ceramics is their low fracture toughness and poor mechanical relia￾bility which so far have limited their practical applica￾tions. Thus, methods to improve their fracture toughness and retain their high-temperature creep properties as well as enhance their mechanical reliability are a major challenge. One way to achieve these goals is through the development of composite structures. That is to the ceramic matrices are added dispersed ceramic particles, whiskers or ®bres which reinforce the matrices and improve their mechanical properties. Alumina-based ceramic composites such as Al2O3- Zr02, Al2O3-Y3Al5O12, Al2O3-SiC, Al2O3-TiC, Al2O3- TiCxN1-x composites are widely studied, as to their ambient and high temperature mechanical properties and reliabilities. Great emphasis is placed on their high temperature creep behaviours. The purpose of this paper is to recall brie¯y the major theoretical models for creep and then to review the available information on the plastic deformation beha￾viours of Al2O3-based ceramic composites. Composites reinforced by long ®bres are not discussed here since their fabrication procedures markedly di€er from those based on powder processing which yield materials with dispersed phases. 2. Deformation mechanisms 2.1. The rate equations for plastic deformation The high temperature creep of single phase crystalline materials may be expressed by a relationship of the fol￾lowing form: "_ ˆ A DGb kT b d  p  G  n …1† where "_ is the steady state creep rate, A is a dimension￾less constant, D is the appropriate di€usion coecient, G is the shear modulus, b is the magnitude of the Bur￾gers vector, k is Boltzmann's constant, T is the absolute temperature, d is the grain size,  is the applied stress, Ceramics International 25 (1999) 395±408 0272-8842/99/$20.00 #1999 Elsevier Science Limited and Techna S.r.l. All rights reserved PII: S0272-8842(98)00017-0 * Corresponding author at Nanjing University of Chemical Tech￾nology, 210009, Nanjing, People's Republic of China