Impact of rolling technology on microstructure mechanical properties

Impact of rolling technology on microstructure, mechanical properties and thermal stability of high purity Al sheets M. Slámová 1, P. Homola 2, M. Cieslar 3 1 VÚK Panenské Břežany, s. r. o. , 2 Czech Technical University, Prague, 3 Charles University in Prague

SCHEDULE • Introduction • ARB x conventional rolling • Thermal stability • Mechanical properties • Summary

Ultra-fine grained materials Equal Channel Angular Pressing (ECAP) High Pressure Torsion (HPT) Cryogenic Working … Accumulative Roll-Bonding (ARB)

Advantages of ARB 1. No special equipment 2. Ability to produce large bulk materials

Material Al (99. 99) Cold rolling to thickness 2 mm Recrystallization annealing 350°C/30 min

ARB processing 1) Degreasing and wire-brushing with 0. 3 mm steel wire brush 2) Stacking of two pieces of 300× 50× 2 mm 3 3) Joining by Al wires 4) Rolling without lubricant to 50% reduction in thickness

Conventional rolling Thickness of 1, 0. 5, 0. 25 and 0. 125 mm (the same equivalent strains as obtained by 1 to 4 ARB cycles)

Initial structures

ARB 1 3 2 4

CR 1 3 2 4

CR ARB 2 2 3 3

ARB - TEM 1 3 2 4

CR - TEM 1 3 2 4

CR ARB 2 2 3 3

Temperature stability (ARB)

Temperature stability (CR)

Microstructure (ARB – 3 cycles) Init. 200°C. 250°C. 300°C.

Microstructure (CR – 87. 5%) Init. 200°C. 250°C. 300°C.

Summary • Sheets from high purity Al were prepared by ARB and cold rolling • The evolution of grain shape in CR samples is nearly the same as in ARB materials • The CR material is more thermally stable, recrystallization starts at higher temperature for all strain levels • The properties of both materials are comparable BUT the ARB material preserves its original thickness.