Research into precipitation hardening in additively manufactured (AM) maraging steel is mainly conducted on the material after several hours of holding at the peak hardening temperatures of 450–500 °C. Lower temperatures are expected to have little to no effect on mechanical properties even after very long holds at these temperatures. This article, however, demonstrates that new precipitates grow and cause a noticeable hardening effect in solution-annealed AM maraging steel after only a 6-hour hold at a temperature of 350 °C. High-resolution scanning and transmission electron microscopy (HRSEM, HRTEM) was used to identify the new precipitates. Very fine coherent microdomains containing mainly nickel and molybdenum layers were found. Particles of a new phase, Al0.5CNi3Ti0.5, were also detected. Additionally, various precipitates were also found in both the as-built and the AM solution-annealed maraging steel samples. Precipitates such as Ni3Ti, Al0.3Ni0.35Ti0.35 and Al2O5Ti, were also observed in the as-built condition. After subsequent solution annealing at 820 °C additional Ni3Mo particles and another type of Ti-rich particles, Ni4Ti3, were further found in the AM steel microstructure. The additional new phases which precipitated during the final hardening at 350 °C caused an 18 % (200 MPa) increase in strength.

中文翻译：

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粉末床熔炼马氏体时效钢1.2709的低温沉淀强化

对增材制造 (AM) 马氏体时效钢沉淀硬化的研究主要针对材料在 450–500 °C 峰值硬化温度下保持数小时后进行。即使在这些温度下保持很长时间后，较低的温度预计对机械性能也几乎没有影响。然而，本文表明，固溶退火 AM 马氏体时效钢在 350 °C 温度下仅保持 6 小时后，新的析出物就会生长并产生明显的硬化效应。使用高分辨率扫描和透射电子显微镜（HRSEM、HRTEM）来识别新的沉淀物。发现了非常精细的相干微区，主要含有镍和钼层。还检测到了新相 Al0.5CNi3Ti0.5 的颗粒。此外，在竣工样品和增材制造固溶退火马氏体时效钢样品中也发现了各种沉淀物。在竣工条件下还观察到诸如 Ni3Ti、Al0.3Ni0.35Ti0.35 和 Al2O5Ti 等析出物。随后在 820 °C 固溶退火后，在增材制造钢的显微组织中进一步发现了额外的 Ni3Mo 颗粒和另一种富钛颗粒 Ni4Ti3。在 350 °C 最终硬化过程中析出的额外新相导致强度增加 18 % (200 MPa)。