17–4 PH (precipitation hardening) stainless steel is commonly used for the fabrication of complicated molds with conformal cooling channels using laser powder bed fusion process (L-PBF). However, their microstructure in the as-printed condition varies notably with the chemical composition of the feedstock powder, resulting in different age-hardening behavior. In the present investigation, 17–4 PH stainless steel components were fabricated by L-PBF from two different feedstock powders, and subsequently subjected to different combinations of post-process heat treatments. It was observed that the microstructure in as-printed conditions could be almost fully martensitic or ferritic, depending on the ratio of Cr_eq/Ni_eq of the feedstock powder. Aging treatment at 480 °C improved the yield and ultimate tensile strengths of the as-printed components. However, specimens with martensitic structures exhibited accelerated age-hardening response compared with the ferritic specimens due to the higher lattice distortion and dislocation accumulation, resulting in the “dislocation pipe diffusion mechanism”. It was also found that the martensitic structures were highly susceptible to the formation of reverted austenite during direct aging treatment, where 19.5% of austenite phase appeared in the microstructure after 15 h of direct aging. Higher fractions of reverted austenite activates the transformation induced plasticity and improves the ductility of heat treated specimens. The results of the present study can be used to tailor the microstructure of the L-PBF printed 17–4 PH stainless steel by post-process heat treatments to achieve a good combination of mechanical properties.

17-4 PH（沉淀硬化）不锈钢通常用于使用激光粉末床融合工艺 ( L- PBF)制造具有随形冷却通道的复杂模具。然而，它们在印刷条件下的微观结构随着原料粉末的化学成分而显着变化，导致不同的时效硬化行为。在本研究中，17-4 PH 不锈钢部件由两种不同的原料粉末通过L- PBF制造，然后进行不同的后处理热处理组合。据观察，在印刷条件下的微观结构几乎可以完全是马氏体或铁素体，这取决于 Cr _eq /Ni _eq的比率原料粉末。在 480 °C 下进行时效处理提高了印刷组件的屈服强度和极限拉伸强度。然而，由于更高的晶格畸变和位错积累，马氏体组织的试样与铁素体试样相比表现出加速的时效硬化反应，导致“位错管扩散机制”。还发现马氏体组织在直接时效处理过程中极易形成回复奥氏体，其中 19.5% 的奥氏体相在直接时效处理 15 小时后出现在显微组织中。较高比例的回复奥氏体激活相变诱导塑性并提高热处理试样的延展性。本研究的结果可用于定制微结构L- PBF 通过后处理热处理印刷 17-4 PH 不锈钢，以实现机械性能的良好组合。