Abstract
The GTD 450 stainless steel is a kind of precipitation hardening martensitic stainless steel containing copper. This steel has been found to have numerous applications in the chemical and food industries, and for various compressor components in both gas and steam turbines due to its high strength, ductility and corrosion resistance. In this research, aging behavior has been investigated via optical metallopgraphy, transmission electron microscopy and micro-hardness measurement. The microstructure of solution treatment specimens is composed by lath martensite (with micro-twin) and retained austenite. The hardness of specimens which were aged at 510℃ is higher than the one aged at 590℃. In the over-aging case, the hardness curve of aged at 590℃ decreases faster than 510℃. In the case of 590℃ aging treatment, the reversed austenite has been formed, and the amount of reversed austenite increase with increasing time of aging treatment. The orientation relationship between the reversed austenite and the martensitic matrix has been determined to be [100]bcc//[110]fcc 、(011)bcc //(111)fcc ,which matches the Nishiyama-Wasserman relationship. In the case of aging at 510℃, the reversed austenite is not formed, but the orientation relationship between the retain austenite and the martensite is also N-W relationship.
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