激冷快速凝固Al-Cu共晶合金的层片失稳研究

Destabilization of Lamellar Structure of Rapidly Solidified Al-Cu Eutectic Alloy

目的研究热处理条件下共晶层片组织的失稳机制,通过理论建模定量阐明控制层片失稳的关键因素。方法以Al-Cu共晶合金为研究对象,采用铜模激冷的方法使合金发生激冷快速凝固,获得2个不同冷却速率下的细化共晶层片组织,进一步对所制备的样品进行不同温度及时间的退火处理。研究了退火条件下层片组织的失稳行为,进一步建立了层片失稳的理论解析模型,并基于模型,阐明了热处理条件下共晶层片失稳的机制。结果凝固冷速为63 K/s和28 K/s的2个样品层片组织均发生了失稳,且在相同退火温度下,冷速为63 K/s的样品(初始共晶层片更细小)更易发生失稳,当退火温度及时间相同时,冷速为63 K/s的样品层片失稳程度更高。结论在退火条件下,受瑞利不稳定性的影响,共晶层片失稳遵循由层片组织转为棒状组织、棒状组织转变为粒状组织的演变规律;层片厚度和退火温度是层片粒化的主要影响因素。

The work aims to study the destabilization mechanism of eutectic lamellar structure under heat treatment and quantitatively clarify the key factors controlling lamellar destabilization through theoretical modeling.With Al-Cu eutectic alloy as the research object,the alloy was rapidly solidified by copper mold to obtain two refined eutectic lamellar structures at dif-ferent cooling rates.Further,the samples were annealed at different temperature for different time,and the destabilization be-havior of lamellar structures under annealing conditions was studied.Then,a theoretical analytical model of lamellar destabili-zation was established.Based on the model,the mechanism of eutectic lamellar destabilization under heat treatment was clari-fied.The lamellar structures of the two samples solidified at 63 K/s and 28 K/s were unstable,and the sample at cooling rate of 63 K/s(initial eutectic lamellar was finer)was more prone to destabilization at the same annealing temperature,while the sample at cooling rate of 63 K/s was more unstable at the same annealing temperature for the same time.Under annealing conditions,the destabilization of eutectic lamellar structure is affected by Rayleigh instability,and the lamellar destabilization follows the evolution law from lamellar structure to rod structure and rod structure to granular structure.Lamellar structure thickness and annealing temperature are the main factors affecting lamellar granulation.