气雾化钛合金粉末快速凝固过程模拟

Simulation on the Rapid Solidification Process of Titanium Alloy Powders Prepared by Gas Atomization

气雾化制粉技术是目前制备球形钛合金粉末应用最广泛、最成熟的技术之一。基于流体力学模拟方法,粉末破碎机理研究获得了很大进步。而在气雾化制粉过程中,金属熔滴在高速气流的强制冷却作用下快速凝固形成粉末颗粒,很大程度上决定了粉末的微观组织及性能。针对熔滴快速凝固过程,利用Fluent软件模拟雾化气体与合金熔滴之间的热量传输过程,揭示熔滴快速凝固过程中固液相分布规律。结果显示,随着雾化压力增加,气流汇聚中心轴线上的最大气流速率由190增加到290 m·s^(-1);在不同气流速率的作用下,钛合金熔滴凝固速率达到10^(3)~10^(4) K·s^(-1);随着熔滴粒径减小或者气流速率增加,熔滴凝固速率均逐渐增加。熔滴凝固过程中,气流流动导致熔滴表面传热不均匀,造成熔滴内部出现不均匀凝固过程。

Gas atomization is the most widely used and mature technology to prepare spherical titanium alloy powders.The formation process of the powders,especially the breakup mechanism,has been revealed by the computational fluid dynamics approach.But for the gas atomization process,metal droplets rapidly solidify and form powders under the forced cooling of high-speed gas flow,which primarily determined the microstructure and properties of the powders.In this study,Fluent software was used to simulate the heat transfer process between the gas flow and the droplet to reveal the rapid solidification process.The results indicated that,for the present atomizer,with the increase of atomization pressure,the maximum gas velocity on the central axis increased from 190 to 290 m·s^(-1).The solidification rate of titanium alloy droplet reached 10^(3)~10^(4) K·s^(-1) under the action of different gas velocity.With the decrease of droplet size or the increase of gas velocity,the solidification rate increases gradually.In the rapid solidification process,the gas flow leads to the uneven heat transfer on the surface of the droplet,resulting in the heterogeneous solidification process inside the droplet.