低密度高锰高铝钢的动态变形行为及韧脆转变机理研究

Low density high Mn and Al-content steel has a great potential and a promising prospect in automobile industry because of the excellent combinations of low density, ultrahigh strength and ductility. The project aims to uncover the dynamic deformation behavior of low density high Mn and Al-content steel and find the mechanism of brittle to ductile transition under dynamic loadings by recourse to the dynamic tensile tests under different temperatures (~-196℃ to RT) and strain rates. The dependency of material mechanical response to temperature and strain rate will be analyzed. Then, the temperature and strain rate effects on distribution of dislocation and twinning, and the kind and mobility of dislocation and shear band induced by strain rate will be investigated by extensive microstructure analysis. Also, the interactions of twinning, dislocation, shear band and k-carbide and the mechanism of influence of defects induced by low temperature and strain rate on dislocation mobility will be discussed. The mechanism of high strain rate induced twinning and local heating suppressed twinning will be revealed. Additionally, the transition of deformation mechanism and mechanism of brittle to ductile transition under dynamic deformation of low density high Mn and Al-content steel will be discovered. Finally, Under the condition of temperature and strain rate coupling of viscoplastic constitutive equation of low density high Mn and Al-content steel will be build, which will provide the theoretical and processing basis to optimize the microstructures and improve mechanical properties for low density high Mn and Al-content steel.

低密度高锰高铝钢具有低密度和超高强塑性在汽车工业具有良好的应用前景。针对低密度高锰高铝钢在动态变形下变形机制发生转变的现象，以及在动态变形下的韧脆转变机理尚不清楚等问题；对低密度高锰高铝钢在不同温度(室温至-196℃)和应变速率下实施拉伸试验，分析低密度高锰高铝钢的力学响应对温度、应变速率的依赖性；研究温度和应变速率对位错和孪晶分布、位错种类和位错运动以及可能诱发剪切带等缺陷的影响规律，揭示多缺陷与纳米尺度k-carbide之间的交互作用机理，阐明高应变速率诱发孪晶机制和局部温升抑制孪晶机制产生的条件；揭示在不同应变速率和温度下低密度高锰高铝钢的微观变形机制和韧脆转变机理，建立温度和应变速率耦合条件下的低密度高锰高铝钢粘塑性本构方程，为低密度高锰高铝钢的性能优化和广泛应用提供基础。

低密度钢具有轻量化和高的强塑性，在汽车行业和工程机械行业具有良好的应用前景。本项目选取Fe-Mn-Al-C系中高锰高铝钢作为实验钢，系统地研究了合金元素和应变速率对Fe-Mn-Al-C系中高锰高铝钢的动态变形行为和韧脆转变机理的影响。明确了低密度高锰高铝钢的力学响应对温度、应变速率的依赖性; 研究了温度和应变速率对低密度高锰高铝钢微观组织演变和变形行为的影响机理，揭示了在不同应变速率和温度下低密度高锰高铝钢的微观变形机制和韧脆转变机理，建立了温度和应变速率耦合条件下的低密度高锰高铝钢本构方程，为低密度高锰高铝钢的性能优化和广泛应用提供基础。