Enhancement in Mechanical Properties of AA5052 Sheet for Small Ship by Cold Roll-Bonding Process

Abstract

A cold roll-bonding (CRB) process was applied to enhance the mechanical properties of AA5052 sheet for small ship. Two and four AA5052 sheets of 1 mm thickness, 40 mm width and 300 mm length were stacked, then roll-bonded to a thickness of 0.5 mm and 1 mm respectively by two-pass rolling after such surface treatment as degreasing and wire brushing. The rolling was performed at ambient temperature without lubricant using a 4-high mill at rolling speed of 6.0m/sec. The as roll-bonded AA5052 sheet was then annealed for 1h at various temperatures from 200 to 500℃. The as roll-bonded AA5052 sheets showed a deformation structure in which the grains are elongated to the rolling direction, however above 300℃ they exhibited the complete recrystallization structure consisting of equiaxed grains, regardless of the stack number. The grain diameter of specimens annealed at high temperatures above 300℃ was smaller in 4-layer stack than in 2-layer stack CRB. Both tensile strength and elongation of the specimens were better in 4-layer stack than in 2-layer stack CRB. The effects of stacking number on microstructure and mechanical properties of AA5052 sheets processed by CRB and subsequent annealing were discussed in detail.