论文部分内容阅读
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。
In this paper, the effects of ferrite-bainite two-phase microstructure on tensile properties and impact toughness of ductile iron were studied. When ferrite ductile iron is austenitized at 900 ℃ and isothermally tempered at 400 ℃ with volume fraction of bainite of 54% and 93%, two peaks appear in both elongation and reduction of area. Experiments show that when the ratio of ferrite and bainite in the best range, it can significantly improve its strength and toughness. X-ray diffraction confirmed that bainite was carbide-free upper bainite. Good toughness can be achieved, mainly due to the carbide-free upper bainite that forms a ring-like structure around the graphite balls, probably because the high strength, high-toughness bainite prevents crack initiation at the graphite-bainite interface result.