3D numerical simulation of heat transfer during horizontal direct crystallization of corundum single crystals

Microstructural Evolution in α-Al2O3 Compacts During Laser Irradiation

“…16 it follows that the traverse rate of the beam must be much less than 0.0094 mm/s. Judging from traditional HDS of corundum monocrystals (Bagdasarov & Goryainov, 2001;Lukanina et al, 2006), v must approach the value of about 0.0027 to 0.0022 mm/s. The presence of a large number of pores of various size in the lower part of the rod (see Figs.…”

“…The compounds α-Al 2 O 3 and α-Cr 2 O 3 are isomorphous and their mutual solid solutions α-Cr x Al 2-x O 3 form a single phase with a corundum structure within the composition range 0 ≤ x ≤ 2. The method of horizontal directed crystallization (HDC) is widely used in the synthesis of large corundum (sapphire) and ruby monocrystals (Bagdasarov, 2004;Bagdasarov & Goryainov, 2001;Bagdasarov & Goryainov, 2007;Lukanina et al, 2006;Hurle,1994;Lyubo, 1975). The HDS method consists in the following (Bagdasarov, 2004): a mixture in the form of a powder, crystal breakage, or ceramic tablets is loaded into a boat-shaped container.…”

“…To obtain a strictly oriented monocrystals, a seeding agent is placed in the top of boat, after which both the moment of crystallization and the shape of the crystallization front in the process of monocrystal growth is monitored. The thermophysical processes play a decisive role in the crystallization of high-quality monocrystals because they are responsible for the generation of substantial internal mechanical stresses, porosity, and high dislocation density (Bagdasarov & Goryainov, 2001;Bagdasarov & Goryainov, 2007;Denisov et al, 2007;;Dobrovinskaya et al, 2009;Lukanina et al, 2006;Malukov et al, 2008). In recent years, along with traditional powder metallurgy methods for the synthesis of corundum ceramics, SLS has been used (Liu et al, 2007;Shishkovsky et al, 2007;Subramanian & Marcus, 1995;Subramanian et al, 1993;Xu et al, 2005), what makes it possible to combine complete and partial melting in a single cycle.…”