2005 Volume 91 Issue 3 Pages 320-326
Tensile fracture and peeling behavior of the Fe-Zn intermetallic coating of galvannealed steel, together with that of the alumina coating of anodic-oxidized aluminum as a reference were studied. The Fe-Zn coating exhibited first multiple-fracture perpendicular to the tensile axis. Then the coating exhibited compressive fracture in the width-direction, followed by powdering and the mode ll-type crack extension in the δ1 layer and in the δ1 layer near the δ1-Γinterface. As a result, the upper ζ+ δ1and ζ+δ1+ Γ1 layers were peeled off and the thin δ1+ Γ1 + Γ and Γ1+ Γ layers remained on the steel. Under further applied strain, the remaining δ1+ Γ1+ Γ and Γ1+ Γ layers were fractured in compression in the width-direction, followed by powdering and debonding at the Γ-ubstrate interface. In such a two times-compressive fracture process, coating layers were peeled of The alumina coating on the aluminum substrate exhibited multiple-fracture perpendicular to the tensile stress as similarly as the Fe-Zn intermetallic coating. Then, when the coating was thin, the multiply-cracked layer fractured in compression perpendicularly to the tensile axis, accompanied by buckling and wedging, resulting in peeling as similarly as the galvannealed coating.