Microstructure and Mechanical Properties of Al2O3/Er3Al5O12 Binary Eutectic Ceramic Prepared by Bridgman Method

Abstract

Directionally solidified Al2O3/Er3Al5O12 (EAG) eutectic ceramic was prepared via vertical Bridgman method with high-frequency induction heating. The effects of the growth rate on the microstructure and mechanical properties of the solidified ceramic were investigated. The experimental results showed that there were no pores or amorphous phases in the directionally solidified Al2O3/EAG eutectic ceramic. Al2O3 phase was embedded in the EAG matrix phase, and the two phases were intertwined with each other to form a typical binary eutectic “hieroglyphic” structure. With the increase of growth rate, the phase size and spacing of the solidified Al2O3/EAG ceramic both decreased, and the growth rate and phase spacing satisfied the λ2v ≈ 60 formula of Jackson-Hunt theory. The cross section microstructure of the solidified ceramic always exhibited an irregular eutectic growth, while the longitudinal section microstructure presented a directional growth. The mechanical properties of the solidified ceramic gradually increased with the increase of growth rate, and the maximum hardness and fracture toughness could reach 21.57 GPa and 2.98 MPa·m1/2 respectively. It was considered that the crack deflection and branching could enhance the toughness of the solidified ceramic effectively.

The Role of Thin-Film Vacuum-Plasma Coatings and Their Influence on the Efficiency of Ceramic Cutting Inserts

“…When it comes to discussing cutting tools made of ceramics, one of the most effective modern tool materials for the high-speed machining of hardened blanks, things are not so straightforward. On the one hand, the types of ceramics based on Al 2 O 3 and Si 3 N 4 used in the production of the instruments initially have a high hardness, which is more than 20 GPa, and a low friction coefficient within the range of 0.2-0.4 (compared with the tools mentioned above from high-speed steels and hard alloys), i.e., indicators that are comparable with the corresponding values of thin-film coatings based on the nitrides and carbonitrides of refractory metals [4][5][6][7]. On the other hand, ceramics (even the most modern brands of reinforced and composite ceramics) are inferior in regards to their strength characteristics compared to better grades of carbide and, especially, to high-speed steels.…”

Uniformity of Thermoluminescence and Optically Stimulated Luminescence Signals Over the Length of Doped LiMgPO4 Crystal Rods Grown by Micro-Pulling-Down Method

“…Instead of the expected single-crystal structure, we observed a more complex multiphase substructure in all the samples, irrespective of whether they were doped with Tb or Tm ( Figure 12 , Figure 13 and Figure 14 ). Between “smooth” areas, which may indicate the presence of one phase of LiMgPO 4 , there are “hieroglyphic” areas that resemble eutectic alloys [ 37 ]. It is possible that when the crystal pulling process is too fast, thermal conditions result in crystal solidification, which produces multiphase eutectic-like inclusions.…”

Microstructural Stability and High Temperature Strength of Directionally Solidified Al2o3/Er3al5o12/Zro2 Eutectic Ceramics

“…Electronic copy available at: https://ssrn.com/abstract=4375638 P r e p r i n t n o t p e e r r e v i e w e d -2 -temperature have attracted much attention, and a series of research progress has been made [2]. For example, Song et al improved the processing parameters of Bridgman method, and obtained the Al 2 O 3 /EAG eutectic ceramics with hardness up to 21.57 GPa [3]. Pastor et al prepared Al 2 O 3 /Y 3 Al 5 O 12 (YAG)/ZrO 2 eutectic ceramics with the micro pulling down method (µ-PD), the sample' flexural strength reached 3 GPa, which was much higher than that of the advanced Si 3 N 4 ceramics (550 MPa) [4].…”