MECHANICAL PROPERTIES OF ALUMINUM SHEETS AFTER ACCUMULATIVE ROLL BONDING USING TWO AND FOUR-HIGH ROLLING MILL

Abstract

This paper emphasized that there are a number of factors contributing to slightly different mechanical properties of aluminum sheets after rolling using a two or a four-high rolling mill. The major ones are the roll diameter, angular velocity, deformation zone, and surface roughness. In two-high rolling mill required annealing of the edges of the sheets, which was used to suppress the development of cracks. While higher rolling speed of the four high mill leads to higher deformation rates and a smaller deformation zone to higher pressures the in-between annealing of the edges, which was necessary on the two-high rolling mill allowed for prior precipitation evolution and therefore strengthening. The development of the oxide layer on the rolls of a two-high rolling mill was more rapid than on the rolls of a four-high rolling mill, because of relatively old and worn out surfaces, higher surface roughness as well as a bigger roll diameter. Thus, the mechanical properties of the sheets produced by a two-high and of four-high rolling mill cannot be directly compared. It is also worth pointing out that the hardness evolution of samples rolled using a two-high rolling mill preceded more quickly within the first 6 ARB cycles, but then subsided more quickly compared to a four-high rolling mill.