Interfacial Reaction in Twin-Roll Cast AA1100/409L Clad Sheet During Different Sequence of Cold Rolling and Annealing

Abstract

Besides cold rolling reduction and annealing temperature and time, sequence of cold rolling and annealing also affects interfacial reaction in twin roll cast (TRC) clad sheet. This is because of short contacting time between Al melt and steel and small rolling reduction in as-cast TRC sheet, which results in small and uneven distribution of metallurgical bonding in the sheet. In as-cast sheet, no intermetallic compound (IMC) appears at the bonding interface after 510 °C × 1.5 h annealing and the sheet has a high peeling strength of 21.5 N/mm. However, incubation period of IMC is shortened in the 40% cold rolled sheet. A 2.2 μm thick IMC layer appears in the 40% sheet after 510 °C × 1.5 h annealing and the peeling strength decreases to 15.5 N/mm. 25% reduction cannot reduce the incubation period. This is because the bonding interface becomes tight enough and its energy storage increases after 40% cold rolling and as a result, the inter-diffusion of Al and Fe atoms is enhanced during annealing.