The study of 18R martensitic transformation in Fe-Mn-Al steels

• Main Authors: Shao-Chi Kao, 高紹騏
• Other Authors: Shyan-Kay Jou
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/vzurpq

碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 104 === Fe-C-Mn-Al steels with the potential to replace some Ni-Cr stainless steels have been studied for decades. Phase transformations are the basic requirement for the development of Fe-C-Mn-Al steels. We have studied the 18R martensitic phase transformations of steel A with the composition of Fe-0.098 C-28.5 Mn-8.8 Al and steel B Fe-0.28 C-19.6 Mn-7.7 Al in various heat treatments including heating to temperatures from 1350℃ to 1100℃ and cooling by water-quenching and/or air-cooling. Alloy A is composed of ferrite grains which are occupied by 18R martensitic plates after quenching from 1200℃ and/or above. At 1150℃, some 18R martensitic plates appear in ferrite with a dual-phase structure. No 18R martensite forms in the ferrite of the dual phases at 1100℃. So we confirm that the low temperature limit for the formation of 18R martensite of the steels locates at temperature between 1150℃ and 1100℃. Alloy B is composed of ferrite and austenite at temperatures above 1100℃. After water quenching at 1150℃ or above, the 18R martensitic plates appear in the ferrite grains with the grain size larger than the critical value. We have also observed the needle-free zones in the ferrite grains located nearby the austenite grains.