基于铸锭均质化窗口的熔体离散-增材铸造研究

The inhomogeneity in ingots not only decides the final properties of the product, but also restricts downstream hot working processing severely. Conventional pouring method with fixed alloy component and continuous pouring, cannot meet both the superior performance and low cost requirement with a complicated alloy compositions.. In this project we propose a Discrete-Liquid-Additive-Materials solidification (DLAMs) technique for the casting of heavy ingot by diverging the liquid alloy melt, intermittence pouring, and fractional step solidification. With this DLAMs technique the melt flow zone is decreased with a suppressed flow velocity. The cooling rate at the later solidification stage for each discrete melt will be dramatically increased. The alloy component will also be able to be varied based on the instantaneous solute content of the remained unsolidified melt, which subsequently could significantly reduce macrosegregation of heavy ingot. Therefore, this technique will increase the homogeneity level of the ingot with a higher yield of the materials and reduced energy consumption. .A discrete pouring procedures and models for both fixed and unfixed alloy component DLAMs techniques will be built in this project based on the solidification theory and experiment results. The effects on the final crystal structure and macrosegregation distribution for heavy ingots will also be investigated. A general model for the technique will be built up based on the macrosegregation level requirement with the pouring procedures, the melt time control, and the alloy component control (for unfixed alloy component DLAMs technique).

铸锭的不均匀直接影响最终产品的性能，并严重制约后续热加工方法和工艺窗口选择。随着合金更复杂、铸锭尺寸更大和对产品性能窗口要求的提高，传统定成分同时浇注的铸造方法无法满足高品质高合金材料铸造和低消耗制造的要求。本项目通过合金熔体离散、间歇浇注、分步凝固的增材铸造，减小铸型内熔体的流速和流动区域、增大铸锭凝固后期的冷却速率，并根据铸锭实时凝固溶质分凝状态确定后续浇入熔体成分、降低宏观偏析，实现提高铸锭均质化水平和材料利用率、降低能源消耗的目的。在前人对铸锭组织和偏析形成的研究成果的基础上，研究定成分和变成分两种情况离散-增材铸造下满足所需均质化窗口的浇注模式和程序、离散-增材铸造模式对铸锭组织和成分分布的影响，建立基于目标成分偏析水平的熔体离散和合金冶炼时间控制模型以及变成分离散冶炼的成分控制模型，发展离散-增材铸造的通用模式程序。为大尺度、复杂合金铸锭的高均质化低消耗制造提供理论和技术基础。

铸锭的不均匀直接影响最终产品的性能，并严重制约后续热加工方法和工艺窗口选择。随着合金更复杂、铸锭尺寸更大和对产品性能窗口要求的提高。为了解决传统定成分同时浇注的铸造方法无法满足高品质高合金材料铸造和低消耗制造的要求问题，本项目深入研究了通过合金熔体离散、间歇浇注、分步凝固的离散-增材铸造控制方法的基本原理、控制及其应用。.开展了合金熔体的离散-增材铸造控制方法及控制机制，离散-增材铸造过程中金属液在铸型中的宏、微观流动，离散单元的凝固行为和单元间的相互作用，离散-增材铸造过程离散单元的耦合行为，离散-增材铸造过程离散单元的耦合行为五个方面的研究。.通过这五方面的研究获得了以下研究成果：成功实现了100公斤级Al-4.5wt%Cu合金铸锭的离散-增材制备；发展了离散-增材铸造方法的浇注理论，实现了铸锭凝固过程的全时段调控；建立了离散增材铸造全过程耦合数值模拟模型，建立了基于目标均质化窗口的离散-增材铸造浇注程序控制模型，实现铸锭成分偏析的设计和控制；深入研究了离散合金熔体增材铸造中的耦合凝固行为，探讨了其控制因素、金属熔体在铸型中的宏微观流动及其对组织和偏析的影响，实现不同时段浇入熔体的最优化耦合连接；自行搭建了离散-增材铸造实验平台，并结合数值模型建立了基于目标的离散-增材铸造铸锭的全流程控制程序，初步构建了铸锭离散-增材铸造过程的全流程数字化程序；发展了离散-增材铸造的通用模式程序。本项目的研究成果为大尺度合金铸锭的高均质化低消耗制造提供理论和技术基础。