Influence of homogenization on the microstructure, mechanical properties and texture of the twin-roll cast AA8006 sheet processed by accumulative roll-bonding

Miroslav Karlík,Petr Homola,Jiří Čapek,Petr Harcuba,Peter Sláma,F De Geuser,A Deschamps,G Salloum-Abou-Jaoude,J.-C Ehrström,L Salvo,P Jarry,C Sigli

doi:10.1051/matecconf/202032605003

Abstract

Unhomogenized and homogenized AA8006 (Al-Fe-Mn-Si) alloy sheets twin-roll cast to strip 8.5 mm thick, processed by accumulative roll-bonding (ARB) on 2 mm thick sheets up to 6 cycles were studied. The microstructure was characterized by means of scanning and transmission electron microscopy and electron backscattered diffraction (EBSD), mechanical properties were monitored by hardness measurements and tensile tests. The macroscopic texture was determined by X-ray diffraction. The initial texture of the unhomogenized sheet is rotated cubic {001}<110> combined with recrystallization R texture {011}<211>, while the homogenized sheet has a cubic texture {001}<100> with remaining rolling component C {112}<111>. One ARB cycle leads to the formation of low-angle grain boundaries (LAGB) in original coarser grains and to a low angle rotation of the subgrains bounded by LAGB. After the 3rd and 6th ARB cycle unhomogenized and homogenized sheets show a common rolling texture of cold-rolled aluminium. The thermal stability of sheets processed by 6 ARB cycles was tested by isochronal annealing for 30 min up to 450°C. The homogenized sheet starts to recrystallize at 250°C, while the fine grain structure of the unhomogenized sheet is thermally stable up to 400°C.

Highlights

Accumulative Roll-Bonding (ARB) is a technique of grain refinement by severe plastic deformation (SPD) proposed by Saito et al [1]
ARB does not require any special equipment as other SPD methods such as equal channel angular pressing (ECAP) [2], high pressure torsion (HPT) [3], or cyclic extrusion and compression (CEC) [4], but only a conventional rolling mill
The softening behaviour of the homogenized AA8006 sheet processed by 6 ARB cycles, i.e. the onset of recrystallization at 250°C is similar to the results reported for the same homogenized alloy in [20] after 3 and 5 ARB cycles

Summary

Introduction

Accumulative Roll-Bonding (ARB) is a technique of grain refinement by severe plastic deformation (SPD) proposed by Saito et al [1]. Since the sheet thickness remains unchanged by this cycle, ARB processing can be repeated as many times as desired, and an extremely high plastic strain is imposed on the material, resulting in structural refinement and increase of strength. An energy efficient technology of twin-roll casting (TRC) is known to produce materials with fine particles and small grain size, which are good starting materials to further grain refinement by ARB processing. A substantial grain refinement by ARB could be accompanied by dissolution and reprecipitation of second phase particles [8,15]. It can have a similar effect as homogenization. A study of the homogenization and ARB processing on the microstructure, texture and mechanical properties of a commercial TRC AA8006 alloy is presented

Results

Discussion

Conclusion