铍铝合金挤压铸造凝固行为及其微观组织形成机理研究

项目名称： 铍铝合金挤压铸造凝固行为及其微观组织形成机理研究

项目编号： No.51504226

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 矿业工程

项目作者： 王晶

作者单位： 中国工程物理研究院

项目金额： 19万元

中文摘要： 铍铝合金具有宽的凝固区间，熔化潜热高、热扩散能力低，凝固组织为粗大的柱状晶，热裂倾向严重。通过对液态金属施加机械压力能够补偿凝固收缩，提高热散失能力，并使铸件产生少量塑性变形，有望使铍铝合金获得致密、均匀的组织和优异的性能，解决高质量铍铝合金生产的难题。然而，目前对铍铝合金在压力作用下的凝固过程缺乏认识，其组织特性与形成机理还不清楚。本项目关注铍铝合金挤压铸造过程中的基础科学问题，拟利用冷却曲线计算机辅助分析（CA-CCA）研究压力对初生Be相以及共晶组织形成与终了温度的影响规律，阐明凝固过程中固相的生长规律及机理，弄清晶粒尺寸、二次枝晶臂间距、共晶组织体积分数在压力作用下的变化规律，揭示凝固组织的形成机理，明确铝的固溶度与压力的关系，丰富铍铝合金的凝固理论，为航天用铍铝合金大尺寸部件的研制提供理论基础与技术支撑。

中文关键词： 铍铝合金；挤压铸造；凝固行为；凝固组织；力学性能

英文摘要： Due to large freezing range, high latent heat of fusion, and low capability of heat diffusion, Be-Al alloy exhibits coarse columnar dendritic structure and severe tendency towards thermal cracking. Squeeze casting offers the advantages of solidifying under an external pressure introduces plastic deformation that compensates for volume shrinkage and increases heat rejection capability, which has a great potential for Be-Al alloy to get more compact and uniform structure, and excellent properties. Squeeze casting could be the method to prepared high quality Be-Al billet. At the present time, limit researches have been done about squeeze-cast Be-Al alloy, and the understanding of solidification behavior during squeeze casting process of Be-Al alloy and its effect on microstructure is still limited. In this project, several scientific problems of squeeze-cast Be-Al alloy will be studied. Both the start and end temperatures of primary Be formation and eutectic reaction under the applied pressure will be investigated using computer-aided cooling curve analysis (CA-CCA). The evolution rule of solid fraction during solification will be ravelled, the influence of applied pressure on grain size, SDAS, and eutectic structure fraction and its mechanism will be indicated, the internal relations between morphology of the solid solubility and applied pressure will be definituded. The results of the project will complement solidification theory of Be-Al alloy, and provides the theory basis and technical sustain for developing jumbo size Be-Al alloy parts used in aerospace equipment.

英文关键词： Be-Al Alloy;Squeeze Casting;Solidification Behavior;Solidification Microstructure;Mechanical Properties