G Model MSA-25534:N a orages ARTICLE IN PRESS D Jianxin et aL Materials Science and Engineering A xxx(2009)xxx-XXx (a) (b) Interface Interface AWT 5 mm nterface Fig 3. SEM micrographs of the interface structure of AWT+ AT multilayered ceramic materials. Table 3 Material properties of AwT and AT [411- Compositions(vol%) Density (g/cm) Thermal expansion(10-5K-) Elastic modulus(GPa) Poissons ratio AWT Al2O3/45%(W, Ti)c 650 7250 448 Al,O3/ 55%TiC 4.73 417 0223 geometry of the layered structure, in particular on thickness ratios [8, 12-15]. The overall residual stress field is rather complex an thus difficult to predict by theoretical calculations: while finite ele ment methods give more accurate estimation of residual stresses d the character of their distribution [17, 48, 49]. Therefore, three- dimensional finite element method(FEM)is used as a means of umerically evaluating the residual stresses and their distribution inside the AWT+AT multilayered ceramic materials during fab rication. In view of the symmetry, three-quarter of a cylindrical model, whose geometry and size were taken from actual hot pressed samples, was represented. Fig 4 shows the FEM gridding 42 model for calculation and the coordinates for the stress analysis. An axisymmetric calculation was preferred and steady state boundary conditions were invoked Table 3 lists the material properties of the AWt and aT materials[41 The model is cooled from sinter g temperature 1700C to room temperature 20 C with a uniform temperature field. The results of the residual stresses in LT-4 and LT-7 multilayered ceramic materials with thickness ratio of 8 and 1 during fabrica- tion are shown in Fig. 5. It is indicated that excess residual stresses were formed inside the layered tool materials. Compressive resid- Fig 4. Finite element method gridding model for calculation and coordinates for ual stresses were introduced to AWT external layer, and tensile the stress analysis. Please cite this article in press as: D Jianxin, et al, Mater. Sci. Eng. A(2009). doi: 10. 1016/j. msea. 2009.09.020Please cite this article in press as: D. Jianxin, et al., Mater. Sci. Eng. A (2009), doi:10.1016/j.msea.2009.09.020 ARTICLE IN PRESS GModel MSA-25534; No. of Pages 9 4 D. Jianxin et al. / Materials Science and Engineering A xxx (2009) xxx–xxx Fig. 3. SEM micrographs of the interface structure of AWT + AT multilayered ceramic materials. Table 3 Material properties of AWT and AT [41]. Code name Compositions (vol.%) Density (g/cm3) Thermal expansion (10−6 K−1) Elastic modulus (GPa) Poisson’s ratio AWT Al2O3/45%(W,Ti)C 6.50 7.250 448 0.232 AT Al2O3/55%TiC 4.73 8.014 417 0.223 geometry of the layered structure, in particular on thickness ratios [8,12–15]. The overall residual stress field is rather complex and thus difficult to predict by theoretical calculations; while finite ele￾ment methods give more accurate estimation of residual stresses and the character of their distribution [17,48,49]. Therefore, three￾dimensional finite element method (FEM) is used as a means of numerically evaluating the residual stresses and their distribution inside the AWT + AT multilayered ceramic materials during fab￾rication. In view of the symmetry, three-quarter of a cylindrical model, whose geometry and size were taken from actual hot￾pressed samples, was represented. Fig. 4 shows the FEM gridding model for calculation and the coordinates for the stress analysis. An axisymmetric calculation was preferred and steady state boundary conditions were invoked. Table 3 lists the material properties of the AWT and AT materials [41]. The model is cooled from sinter￾ing temperature 1700 ◦C to room temperature 20 ◦C with a uniform temperature field. The results of the residual stresses in LT-4 and LT-7 multilayered ceramic materials with thickness ratio of 8 and 1 during fabrica￾tion are shown in Fig. 5. It is indicated that excess residual stresses were formed inside the layered tool materials. Compressive resid￾ual stresses were introduced to AWT external layer, and tensile Fig. 4. Finite element method gridding model for calculation and coordinates for the stress analysis