强脉冲电流辅助NiAl烧结/高温塑性变形一体化中的电致塑性研究

NiAl alloy is able to serve in temperature of 1200℃. Hence, it meets urgent demand of new generation supersonic vehicles for lightweight superalloy. It is well known that powder forming is the near-net technology that is promising to solve issues of processing intermetallics. However, mechanical properties of components prepared via powder metallurgy (PM) generally are inferior than that of plastic deformation bodies, resulting in a bottleneck to be solved. The novel idea of this program lies in proposing a new technology of rapid sintering/hot deformation integration of NiAl powders with pulse current. Accordingly, plastic deformation with electric energy, mechanical energy, and thermal energy is highly emphasized in the research. Both microscopic and macroscopic action mechanism of pulse current with deformation will be determined. Meanwhile, thermoelectric characteristics of NiAl alloys prepared by spark plasma sintering (SPS) will be revealed. Thus, the process parameters of NiAl alloys are presumably optimized, arriving at an effective processing window. The research will also investigate deformation characteristics of NiAl alloys at ultrahigh temperature, and explore the electroplastic effect, thereby figuring out microscopic and macroscopic mechanism of pulse current with plastic deformation. Finite element simulation under the condition of multi-field coupling will reveal characteristics of plastic flow in combination of electric field, thermal field, and force field. Through finite element simulation, effect of SPS and deformation on microstructure evolution will be identified. At the same time, PM NiAl alloys will have forging microstructure and accordingly excellent mechanical properties. The integration of fabrication and forming of intermetallics can be realized.

NiAl使用温度可达1200℃，符合我国新一代高超音速飞行器对轻质超高温材料的迫切需求。粉体成形是解决金属间化合物难变形问题的近净成形技术，但其成形构件的力学性能往往低于塑性变形体，这一瓶颈问题有待解决。本项目首次提出脉冲电流作用下NiAl粉末快速烧结/高温塑性变形一体化新技术。电能、机械能与热能综合作用下材料的塑性变形是研究的重点，脉冲电流对NiAl高温塑性变形的宏微观作用机制是需明确的科学问题。研究将揭示放电烧结材料的电热特性，分析NiAl电热超高温塑性变形特征，探索NiAl高温塑性变形过程中的电致塑性效应，揭示脉冲电流对NiAl塑性变形宏微观作用机理；采用多场耦合条件下有限元模拟技术，分析电、热、力三场复合作用下塑性流动特征；解明放电烧结及塑性变形对材料微观组织的演变的双重作用机制，使粉体成形NiAl获得锻造组织与性能，实现金属间化合物的材料制备与成形一体化。

面向我国新一代高超音速飞行器对轻质超高温材料的迫切需求，以NiAl金属间化合物为研究对象，开展脉冲电流作用下NiAl粉末快速烧结/高温塑性变形一体化新技术相关研究。瞄准强脉冲电流对NiAl高温塑性变形的宏微观作用机理、强电流与塑性流动对NiAl材料微观组织演变复合作用机制、电能、机械能与热能综合作用下的相互作用效应等科学问题。具体开展了如下研究：不同脉冲电流参数下NiAl致密体的电热特性，包含脉冲电流与NiAl致密体温度参数的数学模型，数值模拟分析材料温度场分布；放电烧结NiAl材料的高温塑性变形特征，微观组织对高温塑性变形行为的影响规律，脉冲电流对NiAl高温塑性变形的宏观影响效应；脉冲电流作用下材料塑性变形机制，强电流对NiAl高温塑性变形的微观作用机理；NiAl电热锻造过程中组织演变规律，脉冲电流与塑性变形对材料性能改善的双重作用。通过研究，揭示了放电烧结对NiAl材料电阻率的影响规律，明确了脉冲电流作用下NiAl电热特性，掌握了强电流对NiAl塑性变形的宏观作用效应及微观作用机制，解明了电流与高温塑性变形对材料微观组织与性能的改善机理。实现了放电烧结与电热锻造一体化，解决了金属间化合物复杂构件成形难题，使粉末冶金 NiAl构件获得了锻造组织与性能。1200℃下NiAl材料压缩强度达到295MPa。