铁素体-贝氏体球墨铸铁的初步研究

本文研究了不同比率的铁素体-贝氏体两相组织对球墨铸铁拉伸特性和冲击韧性的影响。当铁素体球墨铸铁在900℃奥氏体化,400℃等温淬火,贝氏体体积分数为54％和93％时,延伸率及断面收缩率均出现两个峰值。实验证明,当铁素体和贝氏体的比率在最佳范围时,能明显提高其强度和韧性。X—射线衍射证实,贝氏体为无碳化物上贝氏体。能获得良好的韧性,主要由于在石墨球周围形成环状组织的无碳化物上贝氏体,可能是这种高强度、高韧性的贝氏体在石墨-贝氏体界面阻止了裂纹萌生的结果。

Preliminary Study on Ductile Cast Iron of Ferrite-bainite Duplex Matrix

The infflunce of different ratios of ferrite-bainite duplex matrix on the tensile properties and toughness of ductile cast iron is studied in the paper. When a ferrite ductile cast iron is austenitized at 900C and then austem-pered at 400C, 54% and 93% volume fraction of bainite are abtained, where two peaks appear both in the elongation and in the reduction of cross-sections. The testing has proved that the strength and ductility are remarkably increased when the ferrite and bainite ratio is optimal. The bainite is carbide-free upper bainite phase which has been verified by X-ray diffraction.Obtaining of excellent toughness is basically due to the upper bainite of "eye" structure of carbide-free bainite formed mainly around the graphite nodules. This is probably the result that the bainite has high strength and toughness preventing crack initiation at the graphi-te-bainite inteface.