粉末冶金超细Ti弥散相强化细晶镁合金制备及其力学行为

Aiming to develop a new category of Mg alloy which can not be prepared by melt casting and is featured by low-cost, low-density, high thermal stability and high strength, we suggest that the process of mechanical milling is employed to introduce the light-weight, high strength, and high thermal stability Ti dispersions to the solid solution strengthening magnesium alloys, such as AZ31 and AZ40, to produce, by means of the technology which combines powder metallurgy and deformation processing, the fine-grained Mg alloys strengthened with ultrafine Ti dispersions. A thorough study, at both experimental and numerical simulation level, will be carried out with respect to the preparation and characterization of the mechanically synthesized nanocrystalline Mg alloy powders with ultrafine Ti dispersions and the consolidation of such powders via the warm extrusion process, so as to elucidate the effects of processing parameters on the microstructure evolution as well as the underlying mechanisms. By microstructure observation and mechanical testing of the materials at room and elevated temperatures, the mechanical behaviors and corresponding mechanisms at different loading conditions will be made clear, which will in turn contribute to the well understanding of the relationship between material processing history, microstructure, and mechanical properties, the elucidation of the strengthening and failure mechanisms at different loading conditions. Furthermore, the fundamentals and methods for controlling the microstructure and mechanical properties of the as-processed materials will be clarified. By the research work of the present project, both the Ti dispersion strengthened Mg alloy system and the processing technology will be established, which will lay the basis for their engineering application.

首次提出利用机械球磨技术向固溶强化型镁合金（AZ31、AZ40等）中引入轻质、高强、高热稳定性的金属Ti弥散强化相质点，突破熔炼法不能制备这类镁基材料的局限，以粉末冶金与塑性变形相结合的技术途径，制备出超细Ti弥散相强化型细晶镁合金材料，创立一种新型的低成本、轻质高强耐热镁合金材料体系。系统开展机械球磨Ti弥散强化纳米晶镁合金粉末的制备及其温挤压固结致密成形数值模拟与工艺研究，阐明工艺参数对材料组织结构演变的影响规律与机理。通过对材料微观组织结构及室温与高温力学性能研究，揭示其在不同变形条件下的力学行为与微观机制，建立材料微观组织结构、力学性能、制备工艺三者之间的内在联系，阐明材料的强化机制及其在不同加载条件下的失效机理，提出材料组织性能的控制原理与方法。通过本项目研究，确立超细Ti弥散强化型细晶镁合金材料体系及其制备工艺方法，为其工程化应用奠定基础。

镁合金当前最轻质的金属结构材料，在航空航天、轨道交通、电子通讯等领域，其应用前景广阔。但是，现有工业镁合金的强度低、耐热性能差，难以满足作为高端轻质结构材料的需求。鉴于传统镁合金的上述不足，本项目提出采用机械球磨与塑性变形致密化相结合的工艺方法，制备超细Ti粒子弥散强化超细晶镁合金材料，开辟一条制备轻质、高强、耐热镁合金材料及其制件的新技术途径。.本项目针对Ti弥散强化镁合金粉末制备、粉末体塑性变形致密、材料组织性能控制与力学行为等基础科学与工艺技术问题，开展了深入系统的研究，主要完成了如下工作：（1）确立了Ti弥散强化纳米晶镁合金粉末的机械球磨制备工艺，阐明了球磨参数以及Ti含量对合金粉末组织结构演变的影响规律与机理，获得了最佳球磨工艺参数的取值范围。（2）获得了机械球磨Ti弥散强化镁合金粉末的常温压制特性，揭示了球磨工艺及Ti含量对粉末压制模量与硬化指数的影响规律与机理。（3）阐明了机械球磨Ti弥散强化纳米晶镁合金粉末的热稳定性，建立了晶粒长大的动力学方程，揭示了Ti弥散强化镁合金在加热过程的组织演变规律、机制及Ti质点对镁合金晶粒长大的影响机理。（4）研究了Ti弥散强化纳米晶镁合金粉末的热压制坯与挤压致密工艺，制备出了组织细小致密的Ti弥散强化镁合金挤压棒材，阐明挤压工艺参数对材料致密度与组织性能的影响规律与机理。（5）研究了挤压态Ti弥散强化镁合金室温与高温力学性能，揭示了Ti弥散强化镁合金的室温、高温力学行为及其与材料组织结构的内在联系，阐明了Ti弥散强化镁合金的室温与高温强化机理。.通过本项目的研究，开发出一类新型Ti弥散强化高强耐热镁合金材料体系，确立了这类材料的制备工艺方法，解决了相关的基础科学问题，突破了关键工艺技术难点，掌握了工艺规律，为该类材料的制备与工程实际应用奠定了基础。本项目取得的研究成果，不仅丰富了先进镁合金材料制备及相关领域的基础理论，而且对推动镁合金材料向高端结构应用的进步具有要意义。