The microstructure, mechanical strength, and fatigue response of metal active gas (MAG) butt‐welded G20Mn5 cast steel was thoroughly investigated for exploring the service safety and reliability of new‐generation railway bogie frames. The fatigue properties of the matrix and welded joints were determined by both low‐ and high‐cycle service regimes. On the basis of nanoindentation testing, the fatigue crack growth (FCG) was derived by correlating with cyclic plastic response of microdomain materials across the MAG joint. The results show that the MAG induces considerable changes in microstructures and hardness of the G20Mn5 matrix and resultantly produces an overmatching welded joint but show comparatively low‐ and high‐cycle fatigue properties to as‐received material. The calculated threshold FCG range based on the Murakami model indicates that the maximum 1.5‐mm defect might be the cracking site subjected to fatigue loading from the structural integrity viewpoint.

中文翻译：

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MAG焊接G20Mn5铸钢的组织，力学性能和疲劳性能

对金属活性气体（MAG）对接焊接的G20Mn5铸钢的组织，机械强度和疲劳响应进行了深入研究，以探索新一代铁路转向架构架的使用安全性和可靠性。基体和焊接接头的疲劳特性是由低周期和高周期维修制度共同决定的。在纳米压痕测试的基础上，通过与跨MAG接头的微区材料的循环塑性响应相关，得出了疲劳裂纹扩展（FCG）。结果表明，MAG引起G20Mn5基体的微观结构和硬度发生了显着变化，从而导致焊接接头过匹配，但对所接收的材料显示出较低和较高的循环疲劳性能。