Study on the Microstructure and Mechanical Properties of 17-4 PH Stainless Steel Depending on Heat Treatment and Aging Time
The microstructures and mechanical properties of 17-4 PH stainless steel at each steps of heat treatment, such as homogenizing, solid solution treatment followed by aging treatment, longterm aging at 400 °C, and recovery treatment, in order to obtain a better understanding of the embrittlement phenomena on aging, was investigated. As the homogenizing treatment time increased, the length of δ-ferrite decreased and elongated shape of δ-ferrite turned to sphere shape with the decrease of volume fraction. The solution treated specimen mainly consists of lath martensite with a small fraction of elongated δ-ferrite. The spherical particles existed a little in the martensite matrix, while no precipitates were found in the δ-ferrite at the solution treated specimen. As the aging treatment temperature increased, the strength decreased while the toughness increased. The fcc Cu-rich particles precipitated in the δ-ferrite during the long-term aging at 400 °C after the solution heat treatment. This precipitation causes the aged hardening after long-term aging accompanied by decreases in elongation and charpy V-notch energy absorption. The strength and elongation was restored after recovery treatment and the fcc-Cu precipitated were almost dissolved into the δ-ferrite matrix.
Jang Hyun Sung, Chan Gyu Lee, Yong Zoo You, Young Kook Lee and Jae Young Kim
W. D. Yoo et al., "Study on the Microstructure and Mechanical Properties of 17-4 PH Stainless Steel Depending on Heat Treatment and Aging Time ", Solid State Phenomena, Vol. 118, pp. 15-20, 2006