合金工具钢时变控制半固态触变成形技术的协调变形机制研究

To achieve the near net-shape forming of alloying tool steel products with excellent mechanical properties, and control the phase segregation during semisolid forming effectively, H11 alloy tool steel is employed as the research object. On the basis of the controllable free motion capability of mechanical servo press, an effective time-dependent controlled thixoforming strategy is established, including four stages: partial melting, fast first defamation, short holding, and slow secondary deformation. In partial melting stage, fine globular semisolid slurry with a higher liquid fraction is obtained. In fast first deformation stage, pre-deformation is conducted with higher strain rate. The time and space for out-flow of liquid phase is restrict. In short holding stage, partial solidification decrease the liquid fraction of semisolid slurry. In secondary deformation stage, deformation of the product is completed with lower strain rate. Plastic deformation of solid particles results in recrystallization, and obtain products with excellent mechanical properties. Physical simulation and forming experiments will be conducted to study the microstructural evolution of alloy tool steel during time-dependent controlled thixoforming. The influence mechanism of temperature of semisolid slurries, amount of deformation, and strain rates in different stages on phase segregation will be investigated. An effective controlling mechanism of phase segregation will be established. On the basis of the analysis result of mechanical properties of samples manufactured by time-dependent controlled thixoforming, the dependency relationship between microstructure and mechanical properties of steel products manufactured by time-dependent controlled thixoforming will be established. This study has considerable scientific significance and application prospect.

为实现高性能合金工具钢构件的近净成形，有效解决半固态成形过程中的固液相分离问题，申请人以H11合金工具钢为研究对象，提出时变控制半固态触变成形新工艺。即充分利用机械伺服压力机的柔性和精确的速度及行程控制等特点，将半固态触变成形分解为四个阶段：部分熔融：获得高液相比的球状半固态组织；初锻成形：以较高的应变速率实现预成形，限制半固态坯料中液相外流发生的时间和空间；冷却保持：坯料的液相比因部分凝固而降低；终锻成形：以较低的应变速率完成终成形，大量固相晶粒因塑性变形而发生再结晶等行为，进而获得高力学性能的近净成形件。本项目拟采用物理模拟与成形试验结合的方法，研究H11钢在时变控制半固态触变成形中的微观组织演变规律；探索各阶段坯料温度、变形量、应变速率对固液相分离的影响规律，建立有效的调控机制；分析成形件各部位的力学性能，建立工艺参数、微观组织、力学性能之间的关联模型。具有重要的科学意义和应用价值。

为实现高性能合金工具钢构件的近净成形，有效解决半固态成形过程中的固液相分离问题，项目负责人人以H11合金工具钢为研究对象，提出时变控制半固态触变成形新工艺，传统半固态触变成形、时变控制半固态流变成形、时变控制半固态触变成形示意图如图1所示。即充分利用机械伺服压力机的柔性和精确的速度及行程控制等特点，将半固态触变成形分解为四个阶段：部分熔融：获得高液相比的球状半固态组织；初锻成形：以较高的应变速率实现预成形，限制半固态坯料中液相外流发生的时间和空间；冷却保持：坯料的液相比因部分凝固而降低；终锻成形：以较低的应变速率完成终成形，大量固相晶粒因塑性变形而发生再结晶等行为，进而获得高力学性能的近净成形件。本项目采用物理模拟与成形试验结合的方法，研究H11钢在时变控制半固态触变成形中的微观组织演变规律；探索各阶段坯料温度、变形量、应变速率对固液相分离的影响规律，建立有效的调控机制；分析成形件各部位的力学性能，建立工艺参数、微观组织、力学性能之间的关联模型。具有重要的科学意义和应用价值。