Grain refinement in aluminium and the aluminium Al-Cu-Mg-Mn alloy by hydrostatic extrusion

Hydrostatic extrusion was used as a method for grain refinement in technically pure aluminium and in an aluminium alloy. Both materials were deformed up to a true strain of similar to 4. Such a deformation resulted in substantial grain size refinement to below 1 mu m in aluminium and below 100 nm in the aluminium alloy. In pure aluminium, microstructure evolution proceeds by a continuous increase in the grain boundary misorientation, without changing the grain size. In the aluminium alloy, which has lower stacking fault energy, grains continuously decrease in size, down to the nanometre scale. As a consequence of such microstructure evolutions, the mechanical properties of pure aluminium remain almost constant within a wide range of strains, whereas the mechanical properties of the aluminium alloy are significantly improved. From the present study, one can conclude that hydrostatic extrusion can offer an alternative way to produce nano-metallic elements made of aluminium alloys for light-weight applications.