非晶筋板件强脉冲电加热和箔片汽化冲击热成形机理研究

The crystallization and oxidation during metallic glass hot forming have become bottleneck problems restricting the manufacturing of high-performance rib-web parts. Since current heating can effectively shorten forming duration while foil vaporization can produce high-speed, high-pressure shock, a hot forming technology of metallic glass rib-web parts through high pulse current heating and foil vaporization shock is proposed in this project. By taking advantages of the high pulse current heating, metallic glass billets are quickly heated to elevated temperatures, with their deformability enhanced. Afterward, large plastic deformation in billets is introduced by the shock caused by foil vaporization. By cooperatively controlling the process parameters of fast heating and high-speed shock forming, the forming duration can be significantly shortened so as to avoid crystallization and oxidation. .This project is designed to conduct an in-depth study of the rheological behavior and microstructure evolution regularity of metallic glass under high-temperature and high-strain rate conditions, based on the combination of theoretical, experimental and numerical simulation approaches. The research result can reveal the material flow and microstructure evolution mechanism under the action of thermo-mechanical coupling, and establish the dynamic constitutive model and crystallization activation criterion of metallic glass. Based on the hot plastic deformation principle obtained during high-speed shock forming of metallic glass parts, an integrated control theory and technology for the shape and performance of metallic glass rib-web hot forming parts can be developed, thus, the forming of high-performance metallic glass rib-web parts can be achieved. This project is believed to have important scientific significance and application value for the development of hot shock forming theory and technology of high-performance metallic glass parts.

非晶合金热成形时的晶化和氧化成为制约高性能筋板构件制造的瓶颈问题。本项目基于快速加热能够缩短成形时间和箔片汽化能够产生高速高压冲击的特点，提出一种非晶筋板构件强脉冲电加热和箔片汽化冲击热成形技术，利用强脉冲电流快速加热非晶坯料至高温提高变形能力，随后利用箔片汽化冲击使坯料发生大塑性变形，通过协同控制快速加热和高速冲击成形工艺参数，缩短成形时间，防止非晶晶化和氧化。.项目将通过理论、实验和计算机仿真相结合的方法，深入研究高温高应变速率下非晶合金流变行为和微结构演化规律，揭示热力耦合作用下材料流动和微结构演化机理，建立非晶动态本构模型和晶化激活判据；研究获得非晶合金构件高速冲击挤压热塑性变形规律，建立非晶筋板件热成形形状和性能一体化调控设计理论与技术，实现高性能非晶筋板构件的成形。本研究对发展高性能非晶构件热冲击体积成形理论与技术具有重要科学意义和应用价值。

非晶合金具有高强度、高硬度、高弹性极限等优异性能，其制备及构件成形技术已引起广泛关注。高速成形能够缩短非晶合金热成形的时间，减少表面氧化，并避免晶化，是极具发展潜力的非晶构件成形技术。本项目针对非晶合金筋板构件，采用塑性理论、工艺试验结合数值模拟分析的方法，开展非晶合金箔片汽化冲击成形新工艺研究。.项目主要完成了四项研究内容，包括非晶合金高温高应变速率流变行为和本构建模、非晶微结构演化规律及机理、非晶高速成形的数值模拟建模与分析、以及非晶筋板件高速热成形规律等。通过数据处理、理论分析和数学建模，取得了如下主要成果：1）获得了非晶合金在高温高应变速率的应力应变关系和应变速率敏感性规律，发现变形诱导的纳米晶化导致非晶合金变形能力有所增强，随着应变速率升高，非晶由牛顿流变向非牛顿流变转变，建立了能够准确表征两种流变行为的Maxwell-Pulse型本构模型；2）基于经典自由体积理论，分析了热力耦合作用下自由体积的饱和值、生成量和湮灭量随变形参数的变化规律，构建了考虑尺寸效应的自由体积计算模型；3）建立了非晶合金筋板件冲击成形的分子动力学模拟模型，发现增大筋槽入口圆角有利于材料流动，并显著减小局部应变，而挤压比对材料流动的影响不明显，同时发现非晶内部Voronoi多面体团簇的数量减少，表明冲击波在非晶中的传播破坏了其原有的局部有序结构；4）由成形试验发现，筋板构件高速成形时，由于板平面材料流动困难，应变局部化现象明显，容易导致成形的筋较低或者在筋的背面形成凹陷，因此，获得理想成形结果的冲击能量窗口非常窄。上述结果对理解非晶合金的高速变形机理和结构演变机制具有重要的科学意义，并对成形工艺的优化设计具有重要指导意义。.本项目发表学术论文15篇，其中SCI论文12篇；获发明专利授权2项，申请受理1项；制定国家标准2项；毕业博士研究生2名，硕士研究生3名。

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