Influence of dispersoids on microstructure evolution and work hardening of aluminium alloys during tension and cold rolling

Abstract

The influence of dispersoids on work hardening of aluminium during tension and cold rolling has been studied by comparing Al–Mn alloys containing similar amounts of solutes but various dispersoid densities. The microstructure evolution with deformation strain was examined in transmission and scanning electron microscopy. It is found that a high density of fine dispersoids strengthens the materials significantly, but their strengthening effect diminishes as the strain increases. From a series of Bauschinger tests, it is found that the internal stress, due to particles, increases rapidly at the initial stage of deformation, but saturates at strains larger than 5%. It is concluded that the internal stress makes a small contribution to the work hardening and contributes to less than 10% of the total flow stress during monotonic loading at strains larger than 5%. The work-hardening behaviour has been correlated to the corresponding microstructure, and the strengthening mechanisms are discussed.

Keywords:

• aluminium alloys
• Bauschinger effect
• mechanical behaviour
• strengthening mechanisms
• work hardening

Acknowledgements

The authors are grateful for the assistance of Ning Wang and Pål Christian Skaret with SEM observations and tensile tests, respectively. This work was funded by the Research Council of Norway, Hydro and Sapa Technology, under the project MOREAL.