高速铁路新材料

铝热焊焊接工艺流程会使焊缝材料的力学性能发生改变，从而影响焊接接头的使用寿命，给列车的安全运行带来危害。根据实际焊接工艺设计了铝热焊接头，并从中取样，对比分析了母材和焊缝材料的静力性能、疲劳性能及裂纹扩展性能。试验结果表明：焊缝材料的弹性模量、泊松比、屈服强度与母材较为接近，而塑性、抗拉强度和疲劳性能相比于母材均有不同程度的降低。通过金相试验发现铝热焊焊接工艺使重结晶的焊缝材料晶粒粗大、内部缺陷变多，从微观角度解释了焊缝力学性能降低的现象。研究结果可为钢轨铝热焊的设计与分析提供基础数据。

Thermit welding process changes the mechanical properties of weld material, which will influence the service life of welded joints and affect the safety of trains. In this study, blanks of thermit welded rail were designed, and static tensile test specimen, fatigue test specimen, and crack propagation test specimen were then manufactured from the blanks. The static, fatigue, and crack propagation properties of the base and welding materials were obtained by tests and compared with each other. The results suggest that elastic modulus, Poisson's ratio, and yield stress of the weld material are close to that of base material, instead, the plasticity, tensile strength, and fatigue properties are all lower. A metallographic test was then conducted. It can be observed that the grains of the weld material are coarser, and the internal defects are also more compared to the base material, which explains the deterioration of the mechanical properties of the weld material from a microscopic view. This study provides some basic experimental data and has instructions on the design and analysis of the thermit welded rail.