Kink martensite in a duplex Fe-Mn-Al-C alloy

Abstract

A needle phase within a BCC matrix was found in duplex Fe-Mn-Al-C alloys. It has been identified to have the long period stacking order (LPSO) structure of 18R(5[bar 1])[sub 3] transformed from the BCC parent phase. Later, the LPSO structure was suggested to be a 18R(4[bar 2])[sub 3] martensite phase. Recent reports show that the LPSO structure is close to the 18R(4[bar 2])[sub 3] rather than the 18R(5[bar 1])[sub 3] structure on the basis of high resolution TEM, diffraction patterns and computer simulation. The single shear phenomenological theory was used to calculate te crystallography of this BCC [yields] 18R(4[bar 2])[sub 3] martensitic transformation. The calculated crystallography is in good agreement with experiments and is similar to that of the BCC/18R (or 9R) martensite in other alloy systems. Kink martensites also were often observed in the Fe-Mn-Al-C alloy. Martensite having the kink morphology was also found in Fe-Al-C and in duplex stainless steels quenched from temperatures higher than 1,200 C. However, there has been no report on the crystallographic relationship of the kink martensites. Therefore, the purpose of this paper is to present a detailed TEM analysis and a phenomenological interpretation on the crystallography of kink martensites in the duplex Fe-Mn-Al-Cmore » alloy.« less