Failure Investigation of Cold-Rolled ZnTiCu Alloy Fracture During Bending Under Ambient Temperature Conditions

Abstract

Bending ductility is an important quality parameter of the ZnTiCu rolled sheet for the fabrication of specially formed members in construction industry. Fabrication of such components is usually realized under severe loading conditions (i.e., high strain rate forming using manual tools or press brake machinery) and even sometimes under low temperature environment in the construction field, which is very often close to or less than 0 °C. Bending orientation is also an important parameter, since texture-sensitive Zn alloy cold-worked strip affects ductility performance in direction transverse to the rolling direction. A failure analysis process was implemented on a ZnTiCu bent sheet possessing cracks on outer bent areas. Light optical metallography, and scanning electron microscopy coupled with energy dispersive spectrometry, along with mechanical testing were the principal investigation techniques employed to evaluate the failure. The presence of pronounced elongated grain structure combined with coarse and continuous Ti-rich intermetallic phase, likely reduces the fracture resistance against the transverse stress field imposed by bending, stimulating, thus crack initiation and propagation.