Examination of the binary system Al₂O₃‐ZrO₂ by aero acoustic levitation melting

Abstract

Al 2 O 3 -ZrO 2 composites exhibit excellent mechanical and high-temperature properties. The solidification of various hypoeutectic compositions has been studied by means of aero-acoustic levitation. A high-speed camera recorded the crystallization, to the correlation of the video stills with the observed microstructures. Solidification takes place by formation of several nuclei and subsequent growth. Nuclei are formed in the supercooled melt, entailing to a fine-grained, simultaneously solidified structure. The remaining melt between the growing nuclei is heated due to recalescence leading to primary precipitation of zirconia, followed by eutectic solidification. A consistent behavior is presented to explain the observed microstructures. Additionally, samples between 40 and 50 mol% ZrO 2 exhibit lamellar areas, which exceed the initial zirconia composition. The observed microstructure strongly indicates the existence of a liquid miscibility gap.

Focused Nanosecond Pulsed Laser‐Induced Homogeneous Nucleation in Undercooled Oxide Melts

“…[12,13] Containerless processing is an efficient experimental technique that provides freely suspended droplets with a size of several millimeters. [14][15][16][17][18] Through this approach, induced nucleation at deep undercooling becomes possible. The induced nucleation of solid phase with containerless processing in a undercooled liquid can be initiated using different mechanisms: heterogeneous nucleation, such as probe needle method, [19,20] and homogeneous nucleation, such as cooling rate control.…”

“…The induced nucleation of solid phase with containerless processing in a undercooled liquid can be initiated using different mechanisms: heterogeneous nucleation, such as probe needle method, [19,20] and homogeneous nucleation, such as cooling rate control. [14,15,[21][22][23][24][25] Meanwhile, light controlled nucleation was used as promising primary homogeneous-induced nucleation methods for various transparent supersaturation solutions, such as the nonphotochemical laser-induced nucleation method and laser shock wave method. [26][27][28][29][30][31][32] The thermodynamic driving force for nucleation is the chemical potential (μ).…”