(α+γ)域からオーステンパ処理した球状黒鉛鋳鉄の疲労き裂進展特性

概要

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In the case that the matrix-microstructure of ductile cast iron was changed into the single-phase of bainite by austempering it from γ Phase region(full-austempering), the fatigue crack propagation resistance decreased considerably in the low △K region as compared with that of the as-cast material. In this paper, the effect of austempering from(α+γ)phase region(partial-austempering)was investigated to improve the fatigue crack propagation resistance of ductile cast iron. Fatigue tests were car-ried out at a stress ratio, R=0.1. The matrix-microstructure consisting of the dual-Phase of ferrite and pearlite in the as-castmaterial was changed into the dual-phase of ferrite and bainite by partial-austemperin, and the fatigue crack propagation resistance of the partial-austempered material was higher than that of the as-cast material in the entire △K region. The improvement of fatigue crack propagation resistance was due to the increase of crack closure which was induced by the roughness of the fracture Surface and the formation of the oxide deposits. Furthermore, it was found that the static tensile properties migbt be improved by partial-austempering.
社団法人日本材料学会の論文
1991-01-15