[SY-E6] Symposium E-6

[SY-E6] Delamination cracks in wire-drawn fully pearlitic steels.

^○Masaki Tanaka¹, Yelm Okuyama¹, Tatsuya Morikawa¹, Toshiyuki Manabe² (1.Kyushu Univ., Japan, 2.Nippon Steel & Sumitomo Corporation, Japan)

Wire-drawn fully pearlitic steel was twisted at room temperature. As a result, a delamination crack propagated along the longitudinal direction of the wire. The fracture surface of the delamination crack was compared with the fracture surface obtained by an impact test at 120K, demonstrating that the delamination crack is neither a simple cleavage nor ductile shear one. Backscattered electron and transmission electron microscopy images indicated that the cementite lamellae immediately beneath the delamination crack had vanished. In addition to that, a fine-grained structure was observed. This indicated that the delamination fracture was not a brittle one but a shear one associated with local severe plastic deformation.