纳米晶镁合金粉末微波辅助包套挤压致密化机理研究

针对目前纳米晶镁合金粉末难以全致密化的问题，提出微波辅助包套挤出致密化成形工艺，利用微波辅助驱动作用，实现纳米晶镁合金粉末的完全致密化，同时大幅度提升纳米镁合金材料的性能。与传统的致密化成形相比，送料区的微波辐射属于非接触加热且瞬间温升快速，这对粉体的温度梯度、晶粒成长规律必然带来新的影响；此外，致密成形的应力应变特征及金属流动行为也有显著变化，从微观结构和控制缺陷等诸多方面进行系统深入的研究。本项目主要研究纳米晶镁合金粉末的组织热稳定性、微波辅助对温度梯度及温度传递的影响规律、微波辅助辐射对孔洞湮没的影响机制、挤出参数与微波辐射耦合作用对挤出成形极限的影响机理、微波辅助温度场耦合变形过程中材料的动态流动行为等塑性变形规律，并讨论缺陷形式及形成机制，建立微波辅助-金属包套挤出致密耦合机制的理论。

This project proposes a new way to obtain nanocrystalline bulk magnesium alloy materials, which studies on densification mechanism of nanocrystalline magnesium alloy powders by microwave assisted sheath extrusion. This can greatly improve the performance of magnesium alloy materials. Compared with the traditional densification forming, by applying microwave radiation in extrusion feeding zone, the temperature gradient and grain growth will inevitably bring new influence. In addition, the stress-strain characteristics and metal flow forming also have significant changes, which need related basic theories and technical problems to solve. This project mainly studies on thermal stability of nanocrystalline magnesium alloy powders, the effect of microwave on the temperature gradient and temperature transfer, extrusion parameters and microwave coupling effect on extrusion forming mechanism and material flow dynamic behavior, and discuss the formation of defects and form mechanism, and the formation of defects and form mechanism. The purpose of this project is to establish the theory of densification mechanism of nanocrystalline magnesium alloy powders by microwave assisted sheath extrusion.