高应变速率和高超塑性低中碳钢的合金化设计、超细晶组织调控及超塑性机制研究

Over 100years study, many metals and alloys ,such as Al, Ti, Mg and Cu, were developed to assume the superplastic properties, but the low to medium carbon steel with large quantity of 80% in metallic materials were still non-superplastic materials. With about 5 years research on the alloying design, ultrafine microstructure control and high temperature tensile study, the low carbon steels with high strain rate and high superplastic elongation were developed. In this project, our objective is develop the superplastic low to medium carbon alloy with high strain rate and high elongation by the systemetic study on the alloy design system, ultrafine microstructure control and their superplasticity. The results would give us the relationship among the chemical composition, technique parameters and the superplastic properties of the studied superplastic low to medium carbon steel, clearify the mechanisms of the alloying design, the microstructure control and their superplasticity, which would open a promising way on superplasticity of low to medium carbon steel.

科学家经过近百年研究，开发出Al、Ti、Mg及Cu等超塑性能的金属与合金，但用量超过80%的量大面广的低成本的低中碳钢不具备超塑性特性。经过近5年的低中碳钢的合金化设计、超细晶组织调控以及高温拉伸行为研究，申请者通过FeMnAlC合金化设计和超细晶组织结构调控，开发出具有应变速率和高超塑性延伸率的低成本低中碳钢。本项目计划通过奥氏体稳定化元素(C/Mn)、铁素体稳定化元素(Al)和纳米析出相控制元素(Nb/V/Ti)等合金化设计、超细晶微观组织调控和超塑性行为研究，形成可工业化、低成本、高应变速率和高超塑性延伸率的低中碳钢合金化体系和组织性能调控技术。本研究结果将建立化学成分、工艺参数与超塑性组织性能间的关系，揭示新型低中碳钢的合金化机理、组织结构调控机理以及超塑性机制，开辟出非常具有前景的低中碳钢的超塑性研究方向。

本项目以超细晶和稳定性为方向，进行高应变速率超塑性的低中碳钢合金化设计、基于形变相变和热处理相结合的超细晶组织调控、新型低中碳钢的超塑性理论和新型低中碳钢工业化关键技术等关键科学问题研究。探索了低碳中锰含铝钢获得超塑性的可能性，分别以热轧中锰钢（0.15C5Mn钢和0.15C5Mn2Al钢）和冷轧中锰钢（0.05C5Mn2Al钢、0.10C5Mn2Al钢和0.15C5Mn3Al钢）为研究对象，研究了变形温度、应变速率和原始组织等因素对超塑性能的影响，以及变形过程中的力学行为与微观组织结构的动态演化规律，用高温拉伸试验表征了超塑性，用SEM和EBSD表征了微观组织。热轧含铝中锰钢在750℃、850℃的温度，10-4/s的应变速率下获得了超过100%的超塑性，冷轧含铝中锰钢在750℃~950℃的温度，10-2/s~10-3/s的应变速率下获得了250%~850%的超塑性。完成了项目申报书所有研究内容，为低中碳钢供货态超塑性材料的生产奠定技术保障，推动我国超塑性材料与超塑性成型技术的发展.