オーステンパ球状黒鉛鋳鉄における塊状残留オーステナイトの応力誘起マルテンサイト変態に関する電子顕微鏡観察 [in Japanese] Electron Microscopy Observations of Stress-Induced Martensitic Transformation for Retained Massive γ in Austempered Ductile Irons [in Japanese]
Access this Article
Search this Article
The excellent toughness of austempered ductile irons is considered due to stress-induced martensitic transformation. Stress-induced martensites have however not directly been observed metallographically in austempered ductile irons. TEM and SEM observations were thus carried out on internal and surface microstructures of austempered ductile irons. Ductile iron just austempered consisted of bainitic-ferrite, retained massive austenite (RM-γ) and retained fine austenite (RF-γ). No carbides were observed in the ferrite and on boundaries between the ferrite and austenite phases. On the other hand, lenticular or plate-like martensites with mid-rib and internal twins were observed in the RM-γ of austempered ductile irons subjected to subzero-cooling or fatigue-fracture. It is thus concluded that the excellent toughness is attributed to the stress-induced martensitic transformation in RM-γ, because no martensites were observed in RF-γ.
- Journal of Japan Foundry Engineering Society
Journal of Japan Foundry Engineering Society 73(11), 727-732, 2001-11-25
Japan Foundry Engineering Society