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

Abstract

Induced homogeneous nucleation of undercooling melt is a fundamental challenge with exciting implications for composite ceramic and metal alloy materials. Nucleation can be induced externally, but physical mechanical properties reduce due to the introduction of impurities. Herein, a novel focused nanosecond pulsed laser‐induced nucleation approach is demonstrated for oxide ceramic melts at undercooled state. Using a self‐made aerodynamic levitation setup, the pulsed laser‐induced nucleation is controlled by optimizing the pulse energy density at different undercooled temperatures. Exploiting this approach, nucleation and growth are observed from surface of undercooled alumina (Al2O3) and neodymium yttrium aluminum garnet (Nd:YAG) melts with high‐speed camera. The undercooling sample experiences a nucleate–solidify–recalescence–remelting–recalescence–solidify process. The correlation between nucleation time and undercooling temperature confirms that the undercooled melt is nucleated homogeneously by the pulsed laser. The special microstructural of samples agrees well with the prediction of two‐step nucleation theory. Therefore, an assumption for the nucleation mechanism with the high‐speed images and the microstructure analysis is proposed. This proposed method may provide a different perspective for the classical nucleation theory of homogeneous nucleation.