Influence Factors of Ferrite Cast Iron of Low-temperature Impact Fracture Behavior

doi:10.3901/JME.2016.10.025

Abstract

Abstract: Impact toughness of QT400-18L ductile iron is measured by V-notch Charpy impact test at room and low temperatures. scanning electron microscope(SEM) is used to analyze the impact fracture morphology. The dislocation density near impact fracture surfaces at different temperatures is calculated by X-ray diffraction(XRD) diffraction method. Experimental results show that the energy absorbed by impact test decreases significantly with the decrease of graphite grade. Three damage models of graphite nodules are found during impact fracture. Cracks mainly form at grain boundaries under low temperatures due to dislocation pile-up. Inclusions on grain boundaries lead to the formation of microcavities on dimple fracture. As the temperature decreases, both the density of dislocation and the number of mobile dislocation are decreased. The density of dislocation is about 1.32×10¹⁵m^-2 at room temperature, and the density of dislocation is about 0.39×10¹⁵m^-2at -60 ℃.

Key words: dislocation, ductile to brittle transition, ferrite cast iron, grain boundary, graphite nodules, impact absorbed energy

CLC Number:

TG143

LI Rongde, ZHANG Xinning, JIANG Lipeng, JIANG Ke. Influence Factors of Ferrite Cast Iron of Low-temperature Impact Fracture Behavior[J]. Journal of Mechanical Engineering, 2016, 52(10): 25-31.

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