GAUGE REDUCTION IN TWIN-ROLL CASTING OF AN AA5052 ALUMINUM-ALLOY - THE EFFECTS ON MICROSTRUCTURE

This paper describes the microstructural variations and development fr om the as-cast state through cold rolling and annealing of a Twin-Roll cast AA5052 alloy as a function of critical casting parameters like c asting speed and gauge reduction. By optical characterization, conside rable difference in the as-cast structure is found due to a gauge redu ction from 5mm to 1.9mm, and the cooling rate is reduced in the thinne r strip. These observations are supported by results from computer mod elling of temperature distributions in the process. Higher cooling rat es measured in the surface area are found to influence the later preci pitation and recrystallization in a profound way. Analysis in TEM reve als that the metastable A1(m)Fe is the common primary phase and precip itation of A1(6)Fe starts near the surface after cold rolling acid sub sequent annealing.