高Ca阻燃镁合金近液相线流变成形关键基础研究

In order to improve the poor mechanical properties of high Ca-containing ignition-proof magnesium alloys, a new forming process of high Ca-containing ignition-proof magnesium alloys based on near-liquidus rheo-forming is proposed in this study, i.e. achieving the microstructure refinement of both primary phase and second phase in high Ca-containing ignition-proof magnesium alloys through near-liquidus rheo-squeeze casting process, which is able to improve its mechanical properties effectively as well as insure its ignition-proof performance. Based on above, AZ91-Ca（Ca≥2wt%） ignition-proof magnesium alloy is studied in this project. Argon gas is introduced into the melt in the initial solidification stage to prepare the rheological slurry. The forming ability and microstructure evolution mechanism of AZ91-Ca near-liquidus rheological slurry is studied systematically. AZ91-Ca rheological slurry is shaped by squeeze casting process. The microstructure and mechanical properties of formed components are characterized. The solidification behavior of residual melt under high applied pressure and cooling rate during squeeze casting is studied. The effect of homogenized treatment on microstructure and mechanical properties is also studied. The strengthening mechanism of near-liquidus rheo-squeeze casting AZ91-Ca alloy is discussed. The research is supposed to provide theoretical and experimental basement for the development and application of ignition-proof magnesium alloys and near-liquidus rheo-forming technique.

为克服高Ca阻燃镁合金力学性能上的不足，本项目提出一种新的基于近液相线流变成形的高Ca阻燃镁合金成形方法，即采用近液相线流变挤压铸造工艺实现高Ca阻燃镁合金凝固组织中初生相和第二相的细化，在确保合金阻燃效果的同时有效提高其力学性能。基于此，本项目以AZ91-Ca（Ca≥2wt%）阻燃镁合金为研究对象，通过在凝固初期对合金熔体施加气泡搅拌，系统研究AZ91-Ca阻燃镁合金近液相线流变浆料的形成能力和微观组织结构演变规律；采用挤压铸造工艺对AZ91-Ca阻燃镁合金流变浆料进行成形，研究成形试样的微观组织和力学性能等，探索剩余液相在挤压铸造过程中高压高冷速条件下的凝固行为，研究均匀化处理对近液相线流变挤压铸造AZ91-Ca阻燃镁合金微观组织和力学性能的影响规律，阐明近液相线流变挤压铸造阻燃镁合金的强化机制。研究结果可望为阻燃镁合金以及近液相线流变成形技术的开发和应用提供理论及实验依据。

为克服高Ca阻燃镁合金力学性能上的不足，提出了一种新的基于近液相线流变成形的高Ca阻燃镁合金成形方法，即采用近液相线流变挤压铸造工艺实现高Ca阻燃镁合金凝固组织中初生相和第二相的细化，在确保合金阻燃效果的同时有效提高其力学性能。开发了一套气体搅拌制备阻燃镁合金半固态浆料装置，系统研究了液态挤压铸造AZ91-Ca阻燃镁合金微观组织和力学性能、气泡搅拌制备AZ91-Ca合金近液相线流变浆料组织、近液相线流变挤压铸造AZ91-Ca合金微观组织和力学性能、近液相线流变挤压铸造过程凝固行为、均匀化处理对近液相线流变挤压铸造AZ91-Ca合金微观组织和力学性能的影响。阐明了AZ91-Ca阻燃镁合金在气体搅拌制备半固态浆料过程中非枝晶组织演变规律和形成机制，揭示了流变挤压铸造过程中剩余液相在高压高冷速条件下的凝固行为；探明了流变挤压铸造镁合金的强化机制，提出了提高阻燃镁合金力学性能的有效技术途径。圆满完成了计划书中的研究内容，达到了预期目标。研究结果为阻燃镁合金以及近液相线流变成形技术的开发和应用提供理论及实验依据，对促进镁合金在汽车和航空航天等领域的应用具有重要意义。共发表了标注本基金号的论文21篇，其中SCI收录论文18篇；申请发明专利8项，其中已授权3项；培养博士生3名和硕士生6名。