TiB2颗粒增强超细晶镁基复合材料的组织调控与强韧化机理研究

Magnesium alloy is the key material to reduce the weight of mechanical equipment. However, the lower strength and poor heat resistance severely limit its application in advanced structural components. Therefore, research and development of high-strength heat-resistant magnesium alloy has been the focus of researchers. In this project, the combined methods of high-energy ball milling and plastic deformation densification are used, in order to introduce the ultrafine TiB2 particles into AZ31 Mg alloy with uniform dispersion. The full density TiB2/AZ31 Mg matrix composites will be prepared, which is featured by low density, high strength , excellent thermal stability and ultrafine-grained, achieve magnesium-based composite strengthening and fine-grain strengthening. In addition, the effects of preparation parameters on the microstructure evolution of TiB2/AZ31 magnesium matrix composites will be systematically investigated, which will provide precise control of microstructure for this Mg matrix composites. Moreover, the correlation between microstructure and mechanical properties of TiB2/AZ31 Mg matrix composites will be established, and the effect of TiB2 particles on the mechanical behavior of TiB2/AZ31 magnesium matrix composites was investigated. Therefore, the mechanism of strengthening and toughening of the magnesium matrix composites was clarified, which provided a scientific basis for its engineering application.

镁合金是实现机械装备轻量化的关键材料，但偏低的强度与较差的耐热性能严重限制了其在高端结构部件中的应用，研发新型高强耐热镁合金材料一直是各国学者关注的热点。本项目拟采用高能球磨与塑性变形致密化相结合的工艺途径，在AZ31镁合金中引入均匀弥散分布的超细TiB2颗粒，制备出轻质耐热高强，且具有超细晶基体组织的全致密TiB2/AZ31镁基复合材料，实现镁基复合强化与基体细晶强化的双重强化效果。此外，系统研究制备工艺参数对TiB2/AZ31镁基复合材料组织演变的影响，阐明超细TiB2颗粒对材料组织演变的微观作用机理，实现制备过程中材料微观组织的精确调控。同时，揭示TiB2/AZ31镁基复合材料的微观组织与其力学性能之间的内在联系，探明TiB2颗粒特征对TiB2/AZ31镁基复合材料力学行为的影响规律，阐明该类镁基复合材料的强韧化机理，从而为其工程化应用提供理论指导。

镁合金具有比强度高、比刚度大，易于回收等诸多优点，在汽车、电子通讯和航空航天等领域应用广泛。尽管镁合金的应用需求日益增加，但其在高端结构部件中的应用还很少，主要原因是镁合金的绝对强度低、耐热性能差。因此，研发新型细晶耐热镁合金及其制备成形工艺，已经成为推动镁合金材料向高端结构应用所亟待解决的关键问题，也是当前镁合金材料研究与应用开发的主要方向之一。. 本项目采用高能球磨与塑性变形致密化相结合的工艺途径，制备出了一种轻质耐热高强的超细晶全致密AZ31/TiB2镁基复合材料，实现了镁基复合强化与基体细晶强化的双重强化效果，主要完成了以下工作：(1)揭示了高能球磨过程中，纳米晶TiB2/AZ31镁基复合粉末的组织演变规律，发现了基体细化速率与各工艺参数之间的响应关系以及TiB2颗粒的尺寸的变化规律和在基体中分布的演化规律，确定了合理的球磨工艺参数区间。(2)阐明了球磨后TiB2颗粒增强镁基复合粉末的组织热稳定性与晶粒长大行为，建立了晶粒长大动力学方程，揭示了热处理过程中组织结构演变规律与机理。(3)采用冷压成形、真空热压烧结与包套热挤压相结合的工艺途径，制备出了超细晶全致密AZ31/TiB2镁基复合材料，阐明了不同工艺条件下粉末体固结过程的致密化效果及材料组织结构演变规律与机理，确定了制备超细晶全致密AZ31/TiB2镁基复合材料挤压棒材的最佳工艺条件。(4)研究了超细TiB2颗粒增强镁基复合材料的室温和高温强化机制，揭示了TiB2颗粒对材料力学性能的影响规律及作用机理，探明了超细TiB2颗粒对该类镁基复合材料组织演变的微观作用机理，确立了超细晶TiB2/AZ31镁基复合材料的微观组织结构、力学性能、制备工艺条件三者之间的相互联系，为该类镁基复合材料的制备工艺优化、组织性能控制与工程化应用提供科学依据。. 本项目的开展，为耐热高强镁基复合材料的开发应用奠定了理论基础，进一步推动了镁合金向高端结构部件的应用，具有较高的实际意义和学术价值。.