| dc.description.abstract | The effects of different pore sizes, wall thickness, and heat treatment on the compressive properties of 17-4PH stainless steel hollow spheres preform were investigated.
The results show that the porous preform made from H-PS spheres with large pores (H=4mm), thin wall (l=180μm), and sintered state (AS) exhibits a microstructure composed of plate-like martensite (with a hardness of Hv341) and lath-shaped δ-ferrite (with a hardness of Hv213). Compression testing reveals a plateau stress of 32MPa and an energy absorption capacity of 13.6 J/g. After solution treatment at 1050°C for 1 hour, copper atoms are re-dissolved into the matrix, and the microstructure still consists of plate-like martensite and lath-shaped δ-ferrite, with hardness of Hv308 and Hv208, respectively.
Upon aging treatment at 520°C for 4 hours, copper-rich phase (ε-Cu) precipitates in the matrix. The microstructure observed under an optical microscope remains as plate-like martensite and lath-shaped δ-ferrite, with hardness values of Hv383 and Hv215, respectively. It indicates a significant increase in the hardness of martensite compared to the sintered state, resulting in an increased plateau stress〖(σ〗_pl) of 58MPa and an energy absorption capacity of 24.2J/g. The hardness of δ-ferrite shows no significant change under various conditions. The mechanical properties of the porous preforms, including Hh-AS (large pores, h=250μm), Ll-AS (small pores, l=180μm), and Lh-AS (large pores, h=250μm), exhibit similar trends.
For L-PS sphere-prepared preforms, both the sintered state and aged state show increased density and plateau stress as the wall thickness (180μm, 250μm) increases. In the sintered state, the increase in wall thickness leads to an increase in plateau stress (σ_pl) from 59MPa to 91MPa, but the energy absorption capacity (W) decreases from 24.1 J/g to 19.1 J/g. The H-PS sphere-prepared preforms show improved compressive properties.
Under the same wall thickness (180μm, 250μm) and heat treatment conditions, smaller hollow sphere sizes result in higher plateau stress. It is found that preform with high wall thickness (250μm) and small pores (L-PS spheres), after aging treatment at 520°C, exhibit the best compressive properties with a plateau stress (σpl) of 141MPa and an energy absorption capacity (W) of 33.9 J/g. | en_US |