Based on this theory, the short term tempered martensite plates, subdivide region of austenite, and the
strengthening of matrix is in accordance with the Hall-Petch relationship [2]. In Table4, (MA), it can be
seen that the strength is enhanced by the mixed structure of acicular lower bainite and tempered
martensite. Reduction of strength in UQA is due to the packet size of upper bainite and the reduction of
dislocation density.