1995 Volume 81 Issue 11 Pages 1091-1096
This study is made to clarify the effect of strengthening mechanism of dual phase (ferrite plus martensite phase; DP) steels on the fatigue properties in comparison with ferrite pearlite steels. Several DP steels were obtained to change the kind of strengthening mechanism by adding various alloying elements to the low C-Mn-Cr-Mo DP steel. The strain-controlled and load-controlled fatigue tests were performed. Main results were as follows:
(1) Solid solution strengthening elements, such as silicon and phosphorus, and precipitation strengthening elements, such as niobium and titanium, exhibited a significant increase in fatigue limit. Increasing the carbon content, however, contributed to the fatigue limit to a very small extent.
(2) Considering the fact that the fatigue cracks initiated at the ferrite matrix, not in the second hard phase martensite, the experimental results are explained by strengthening of ferrite matrix being more effective to obtain a high fatigue limit than that of hard phase as well as in ferrite pearlite steels.
