Abstract 24CrNiMo alloy steel is often used to fabricate high-speed railway brake discs. To improve the properties of the alloy prepared via laser melting deposition (LMD) and investigate the role of the rare-earth (RE) element in the LMD of 24CrNiMo steel, three types of powders with different contents of the RE element Y (0, 0.02, and 0.2 wt%) were used. The morphology, composition, and distribution of phases and defects in the alloys were examined using optical microscopy, scanning electron microscopy, electron backscatter diffraction, X-ray diffraction, and transmission electron microscopy. The mechanical properties of the alloys were determined via Vickers hardness and tensile tests. The temperature field and stress field distributions in the forming process were simulated via the finite-element method. The results indicated that adding an appropriate amount of Y (0.02 wt%) can help to reduce defects, refine grains, form a uniform microstructure and fine second phases, and improve the mechanical properties of the alloy. However, adding too much Y (0.2 wt%) causes element segregation, cracks, and large inclusions, which degrade the mechanical properties of the alloy.

中文翻译：

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Y 含量对激光熔化沉积 24CrNiMo 钢的影响：成形性、显微组织演变和机械性能

摘要 24CrNiMo合金钢常用于制造高速铁路制动盘。为了改善通过激光熔化沉积 (LMD) 制备的合金的性能并研究稀土 (RE) 元素在 24CrNiMo 钢的 LMD 中的作用，三种具有不同稀土元素 Y (0, 0.02 和 0.2 重量％)。使用光学显微镜、扫描电子显微镜、电子背散射衍射、X 射线衍射和透射电子显微镜检查合金中相和缺陷的形态、组成和分布。通过维氏硬度和拉伸试验确定合金的机械性能。通过有限元方法对成形过程中的温度场和应力场分布进行了模拟。结果表明，加入适量的Y(0.02 wt%)有助于减少缺陷，细化晶粒，形成均匀的组织和细小的第二相，提高合金的力学性能。然而，添加过多的 Y (0.2 wt%) 会导致元素偏析、裂纹和大的夹杂物，从而降低合金的机械性能。