| Two types of martensitic alloy, Fe-C based martensitic steel (Fe-1.7%C) and Fe-Ni based martensitic alloy (Fe-27% Ni-0.14%C), were prepared and then the retained austenite decomposition behaviors of these alloys were investigated during tempering. The results obtained in this study are as follows. (1) The retained austenite of Fe-1.7%C martensitic alloy begins to decompose into bainite when tempered at 150℃ for one hour. On tempering at 280℃ for one hour, most amount of retained austenite contained in the alloy is transformed to bainite. (2) The integral breadth of retained austenite diffraction line increases as tempering temperature is increased up to about 280℃. This is because volume expansion occurs when the retained austenite is transformed to bainite. (3) In the case of Fe-27% Ni-0.14%C martensitic alloy, the retained austenite does not decompose although tempering is done up to higher temperature such as 430℃. (4) The line broading of retained austenite in the Fe-27% Ni-0.14%C martensitic alloy maintains a nearly constant value during tempering up to about 360℃, and then shows a decreasing value on further tempering at higher temperature than the point. |
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