LAYER THICKNESS EFFECT ON DUCTILE TENSILE FRACTURE OF ULTRAHIGH CARBON STEEL-BRASS LAMINATES

Laminated metal composites containing equal volume percentage of ultrahigh carbon steel (UHCS) and brass were prepared in three different layer thicknesses (750, 200, and 50 mum) by press-bonding and rolling at elevated temperature and were tensile tested at ambient temperature. A dramatic increase in tensile ductility (from 13 to 21 to 60 pct) and a decrease in delamination tendency at the UHCS-brass interfaces were observed as the layer thickness was decreased. The layer thickness effect on ductility is attributed to residual stress whose influence on delamination is decreased as the layer thickness is decreased. Suppression of delamination inhibits neck formation in the UHCS layers, allowing for extended uniform plasticity. For a given layer thickness, the tensile ductility decreases as the ratio of hardness of component layers is increased.