Effects of Aging Heat Treatment and Pore Architecture on the Microstructure and Compressive Behavior of Porous 17‐4PH Stainless Steel

This study investigates the combined effects of aging heat treatment and pore architecture on the microstructure, compressive behavior, and energy absorption performance of porous 17‐4PH stainless steel. Homogeneous, mixed pore‐size, stepwise gradient, and layered porous structures with a fixed porosity of 50% were fabricated using pressureless slurry sintering. Microstructural analyses reveal that aging at 480 °C promotes the formation of fine nanoscale Cu‐rich precipitates (CRPs) within the martensitic matrix, thereby strengthening the pore walls. Based on ISO 13 314, the 480 °C aged specimen exhibits the highest plateau stress of approximately 581.3 MPa and the highest absorbed energy per unit volume at 50% compressive strain of approximately 254.0 J·cm −3 among the heat‐treatment conditions. Further architectural analysis shows that pore‐size arrangement significantly regulates collapse sequence, stress redistribution, and deformation stability. The homogeneous small‐pore structure provides the highest fixed‐strain absorbed energy, whereas the SL gradient structure achieves the lowest stress drop ratio of approximately 5.8%, indicating improved collapse stability. The LSL layered structure offers a favorable balance between high plateau stress and absorbed energy. Overall, integrating aging‐induced pore‐wall strengthening with pore architecture design provides an effective strategy for tailoring the load‐bearing capacity, fixed‐strain energy absorption, and compressive stability of porous 17‐4PH stainless steel.