パンケーキオーステナイト厚さと生成する粒界フェライト厚さの関係

抄録

The grain boundary of the pancake austenite (γ) is a predominant nucleation site for ferrite (α). If the thickness of the pancake γ becomes small through deformation, the thickness of the α grains that are formed at the γ grain boundaries is also expected to become as small as the thickness of the pancake γ. On this basis, the relationship between the thickness of the pancake γ (TH_γ) and that of the grain boundary α (TH_α) is studied both experimentally and theoretically for a 0.16C-0.4Si-1.5Mn steel. When TH_γ is in the range of 30 to 300 μm, TH_α is 6-7 μm and independent of TH_γ. However, when TH_γ is less than 20 μm, TH_α decreases linearly with a decrease in TH_γ. Since the volume fraction of the pearlite is assumed to be 0.25, TH_α is expected to follow the relation TH_α<0.75TH_γ. The obtained relation was near TH_α= 0.375 TH_γ. The geometrical soft impingement is attributed to the decrease of TH_α.