Microstructural evolution in a 17-4 PH stainless steel after aging at 400 C
- National Research Inst. for Metals, Tsukuba (Japan). Materials Physics Div.
- Toshiba Corp., Yokohama (Japan). Heavy Apparatus Engineering Lab.
The microstructure of 17-4 PH stainless steel at various stages of heat treatment, i.e., after solution heat treatment, tempering at 580 C, and long-term aging at 400 C, have been studied by atom probe field ion microscopy (APFIM) and transmission electron microscopy (TEM). The solution-treated specimen consists largely of martensite with a small fraction of {delta}-ferrite. No precipitates are present in the martensite phase, while spherical fcc-Cu particles are present in the {delta}-ferrite. No precipitates are present in the martensite phase, while spherical fcc-Cu particles are present in the {delta}-ferrite. After tempering for 4 hours as 580 C, coherent Cu particles precipitate in the martensite phase. At this stage, the Cr concentration in the martensite phase is still uniform. After 5000 hours aging at 400 C, the martensite spinodaly decomposes into Fe-rich {alpha} and Cr-enriched {alpha}{prime}. In addition, fine particles of the G-phase (structure type D8{sub a}, space group Fm{bar 3}m) enriched in Si, Ni, and Mn have been found in intimate contact with the Cu precipitates. Following spinodal decomposition of the martensite phase, G-phase precipitation occurs after long-term aging.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 316041
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 30, Issue 2; Other Information: PBD: Feb 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Combined atom-probe and electron microscopy characterization of fine scale structures in aged primary coolant pipe stainless steel
The effect of microstructural evolution on hardening behavior of type 17-4PH stainless steel in long-term aging at 350 deg. C