Li Yiyi, female, Han nationality, is a native of JiangSu Province. She graduated from University of Science & Technology Beijing. In the 1990s, Li worked as a researcher at the Metal Research Institute of the of Sciences, and concurrently held the position of superintendent of the Institute.
In her early research on high Mn austenite low temperature steel, she designed the Fe-Mn-Al system phase diagram and the phase appraisal method. Li discovered that antiferromagnetic transformation exists in low temperature and in Fe-Mn alloy, and that the growth of e-martensite core follows fault overlapping and polaxis mechanism. Over the decades, she solved the difficult problem that was previously only theoretically assumed but not verified by experiment. Since 1982, Li has continuously presided over national key science and technology subjects in four "Five-year Plan" periods. She produced five kinds of intensity level hydrogen resistance steel. Li was also responsible for the design of alloy ingredients, thermal processing and phase appraisal, and developed scientific ideas, technical routines and organization for implementation. She is currently specializing in special alloy preparation technology and computer simulation. In recent years, she was responsible for a precision pipeline material base.
Li Yiyi was elected as an academician of the of Sciences in 1993.