高强度镁合金复杂结构件半固态双控成形研究

The development of semi-solid processing in magnesium alloy was seriously limited because of studing alloy and its forming parts with shell parts or no-structure component. In the present study, as a new method, the semi-solid processing is used to produce parts with complex shape by preparing the semi-solid billets of Mg-Gd-Y magnesium alloy with liquid forging in order to meet the imperative requirement both of shape and properties.By studying the preparing of the semi-solid billets,the development of microstructure in the semi-solid state, rheological behavior of alloy in the semi-solid state and thixoforming,the grain size and shape factor will be revealed, the process of thixoforming will be expounded combining with the distribution characteristics of the stress-strain fields,the kinetic model in the solid-liquid will be constructed and the preparing the semi-solid billets method in the high strengh alloy will be proposed. Based on the the process of thixoforming, the research meanings is to supply for preparing the semi-solid billets on high strength alloy and semi-solid processing in forming parts with complex shape.The implementation of this project will promote the development of semi-solid forming theory and its application.

镁合金半固态成形技术主要开发研究铸造镁合金，其成形件多适用于壳体件或非结构件，成为制约镁合金半固态成形技术应用推广的关键问题之一。为满足复杂结构件对成形和高使用性能的双重需求，本项目以高强度镁合金Mg-Gd-Y为研究对象，提出近液相线模锻制坯，最后半固态触变成形复杂结构件方法。通过制坯工艺、半固态微观组织结构、固-液混合体流变行为与触变行为等内容研究，揭示半固态固相微粒尺寸、形状及体积分数与半固态触变行为之间的内在关系规律。探明温度场、流场和力场耦合作用下，应力应变分布特征，构建固-液混合体动力学模型，提出适合高强度镁合金半固态制坯工艺方法。基于半固态触变成形研究，在凝固、变形与补缩交融下揭示固-液塑性变形流动机制及强韧化效应，实现触变成形工艺参数优化及控制。本项目的实施有利于促进镁合金半固态成形理论的发展及半固态成形复杂结构件应用。

为了扩宽镁合金半固态加工技术的应用，选取Mg-Gd-Y、AZ61和AM50镁合金，就镁合金半固态坯料制备、半固态二次重熔和半固态模锻三个环节开展相关的基础理论和应用研究，解决半固态加工技术在成形镁合金复杂结构件的关键技术，并使其强韧化效应达到同类材料的锻造水平。本项目采用试验研究与理论分析相结合的方法，研究了制坯工艺参数对非枝晶化过程的影响规律，坯料在不同保温温度和保温时间下球晶组织的演变规律，半固态合金浆料非枝晶组织的固相分数、固相颗粒尺寸、形状及聚集状态与触变成形过程的充填行为之间的关系。在凝固、变形与补缩交融下揭示固-液塑性变形流动机制及强韧化效应，实现触变成形工艺参数优化及控制。研究成果有利于促进镁合金半固态成形理论的发展及推进其在航天、航空和极端环境下工作制件近净成形中应用。