Mechanical Properties and Deformation Behavior in Severely Cold-Rolled Fe-Ni-Al-C Alloys with Lüders Deformation -Overview with Recent Experimental Results -

It has been reported that severely cold worked Fe-24.6Ni-5.8Al-0.4C (mass%) had a yield strength of 2 GPa and a fracture elongation of 20 %, in which huge amount of Lüders-type deformation was observed. In the present article, we summarize the reports for high-strength Fe-Ni-Al-C, Fe-Mn, Fe-Cr-Ni and Fe-Ni-Mn base steels with the Lüders-type deformation so far, and provide our latest data on the effects of alloying elements and the cold-rolling reduction on the microstructure and mechanical properties of cold-rolled Fe-Ni-Al-C alloys. Previous reports imply that the phase stability of γ phase affects the size of Lüders elongation, while the strategies to control the microstructure to achieve high strength and high ductility are currently unknown. Our latest study also shows that the γ-phase stability affects the Lüders strain. In addition, it is confirmed that severe cold rolling by 80 % enables the prolonged Lüders strain as much as 25 % in nominal strain. This prolonged Lüders strain is achieved by multiple propagation of Lüders-type bands.