纳米粒子孕育下非平衡凝固镁合金异质形核与热稳定性

项目名称： 纳米粒子孕育下非平衡凝固镁合金异质形核与热稳定性

项目编号： No.51461032

项目类型： 地区科学基金项目

立项/批准年度： 2015

项目学科： 一般工业技术

项目作者： 杨伟

作者单位： 南昌航空大学

项目金额： 48万元

中文摘要： 快速凝固对于细化合金组织，提高材料强度、塑性及耐腐蚀性具有显著的作用,然而细晶保持技术是决定其付诸应用的关键。针对工程中常用的镁合金，本项目在搅拌摩擦加工实现纳米SiC均匀分散基础上，采用快速凝固与合金孕育相结合的手段，通过增加熔体中的异质核心、抑制或减弱凝固过程中的传输现象，深入研究非平衡效应作用下的临界形核半径、溶质扩散场局域非平衡与凝固动力学变化行为，最大限度地激发异质核心形核潜力，实现细晶组织的有效制备。同时采用等温退火技术，研究纳米颗粒参与下非平衡凝固镁合金高温晶粒长大行为，构建晶粒长大动力学方程，分析临界晶粒尺寸变化规律,推导不同尺寸及体积分数纳米颗粒影响下的晶粒生长指数、界面迁移激活能及体积分数指数，实现细晶组织热稳定性提高目的。通过研究纳米粒子孕育下镁合金非平衡凝固过程中异质形核与高温热处理过程中晶粒长大两个关键科学问题,为高性能镁合金的研制提供理论依据。

中文关键词： 非平衡凝固；异质形核；枝晶生长；热稳定性；镁合金

英文摘要： Rapid solidification plays an important role for refining microstructure and improving the resultant strength, ductility, as well as the corrosion-resistance property. However, the maintenance of original refined grain is the decisive technique for actual application. On the basis of magnesium alloy with homogeneous dispersion of SiC nano-particulates by friction stir processing, the project proposes a new route with the combination of rapid solidification and alloy inoculation method. By increasing heterogeneous sites, suppression or weaken the transportation phenomenon, the variations of critical nucleation radius, local non-equilibrium effect of solute diffusion field and the transformation process of solidification are investigated under the consideration of non-equilibrium effect. Accordingly, the furthest nucleation potential of heterogeneous sites is expected to be activated to fabricate the ideal refined-grain microstructure. In addition, isothermal annealing is applied to analysis the grain growth behavior of non-equilibrium solidified magnesium alloy inoculated by nano-particulates. After constructing the kinetics equation of grain growth and critical grain size, the grain growth exponent, activation energy and volume fraction exponent can be deduced as functions of the size and content of nano-particulates, so as to improve the thermal stability of refined microstructure. From the above systematical investigation of the two critical scientific issues, i.e., the effects of nano-particulates on the promotion of heterogeneous nucleation for non-equilibrium solidification and suppression of grain growth for isothermal annealing, theoretical guidance is provided to the fabrication of high-performance magnesium alloy.

英文关键词： non-equilibrium solidification;heterogeneous nucleation;dendrite growth;thermal stability;magnesium alloy