Carbon in Bainitic Ferrite of Austempered Ductile Irons

沃斯回火延性鑄鐵中變韌肥粒鐵之碳含量分析

10.6409/JMSE.200503.0030

張柳春(L. C. Chang)；林進誠(J-C Lin)

austempered ductile iron ； bainitic ferrite ； austenite ； carbon concentration

材料科學與工程

37卷1期（2005 / 03 / 01）

30 - 35

英文

An analysis of published data was conducted to examine the amount of carbon trapped, in solid solution or as carbide, in bainitic ferrite of austempered ductile iron. The average values for upper and lower bainite were calculated to be 0.067 and 0.378 wt.%, respectively. Given the large scatter in the data for upper bainite, the usually assumed equilibrium value of 0.03 wt.% is acceptable. However, some upper bainite formed at low temperature can retain as high as 0.36 wt.% of carbon in solution. The fact that both upper and lower bainite can hold up similar amount of carbon is consistent with the postulation that ferrite in both types of bainite grows in an identical mechanism, and then carbon will either precipitate as carbide or partition into the surrounding austenite.