高强度低合金钢带状组织微观结构和力学性能关联性的实验研究

The banded structure is a ubiquitous defect in the high-strength low-alloy (HSLA) steel, which can significantly affect the mechanical properties of HSLA steel. However, the relationship between the banded structure and the macro/micro mechanical properties of HSLA steel is not completely clear so far. Even there are some contradictory results. In this project, based on digital image correlation (DIC), a specific image measurement method will be developed, which can realize the panoramic metallurgical image stitching, measure the macro/micro deformation field, and monitor the damage and fracture. This image measurement method will be applied to multiple experiments. The micro deformation mechanism of ferrite/pearlite band, ferrite/bainite band and ferrite/acicular ferrite band will be analyzed and the micro crack propagation law in different bands will be investigated. The anisotropy of macro mechanical properties of HSLA steel caused by the banded structure will be analyzed and the relationship between the macro damage fracture and the banded microstructure will be discussed. This project is expected to comprehensively reveal the relationship between the banded structure and the macro/micro mechanical properties of HSLA steel. Research results of this project are significant to guide the metallurgical process and the heat treatment process to control the microstructure of HSLA steel scientifically.

带状组织是高强度低合金钢中普遍存在的一种缺陷组织，对钢材力学性能具有重要影响。目前并没有完全明确带状组织和高强度低合金钢宏微观力学性能的联系，甚至一些研究结论存在相互矛盾。本项目拟基于数字图像相关开发具有全景金相图像拼接、宏微观变形场测试、损伤断裂监测功能的图像测量方法。以该方法为实验手段，分析高强度低合金钢中铁素体/珠光体带、铁素体/贝氏体带、铁素体/针状铁素体带三种不同类型带状组织的微观变形机理并探讨微裂纹在不同类型带状组织中的扩展规律；分析不同类型、不同级别带状组织引起的高强度低合金钢宏观力学性能各向异性并探讨带状组织微观结构与钢材宏观损伤断裂之间的联系。本项目预期较为全面地揭示高强度低合金钢带状组织微观结构与其宏微观力学性能的关联性。本项目的研究成果对指导高强度低合金钢的冶炼及热处理工艺以科学控制其微观结构具有重要意义。

带状组织是高强度低合金钢中一种常见缺陷组织，对钢材力学性能具有重要影响。揭示带状组织的种类、取向、形貌等因素与高强度低合金钢宏观力学性能的关联性，对于高强度低合金钢的性能评价非常必要。本项目首先对数字图像相关方法进行了改进，拓展了该方法的应用范围；其次，将扫描电镜下的原位拉伸技术与数字图像相关方法相结合，研究了高强度低合金钢中铁素体/珠光体带状组织和铁素体/针状铁素体带状组织等不同类型带状组织的微观变形机理；再次，测试了含不同类型、不同形貌带状组织高强度低合金钢的宏观力学性能，并利用带状组织的微观变形机理解释了其宏观各向异性。最后，通过疲劳断裂实验探究了带状组织微观结构对高强度低合金钢损伤断裂的影响。该项目的研究成果对指导高强度低合金钢的冶炼及热处理工艺，合理控制其微观结构具有重要意义。