Texture and microstructure in very fine grain Al-Al_3Ti alloys obtained by extrusion of mechanically alloyed powders

摘要

Texture has been investigated in warm extruded Al - Al_3Ti bars obtained from mechanically alloyed powders. The effects of various high volume fractions of Al_3Ti phase (9, 18, and 27 vol.-percent) and the very fine grain sizes that can be obtained via the mechanical alloying processing route are described. Increasing the volume fraction of Al_3Ti phase tends to decrease the anisotropy of the extruded product. The conventional' aluminium texture characterised by a predominant <111>_(Al) fibre usually present in extruded bars is replaced at high volume fraction of Al_3Ti particles (27 percent) and small size of aluminium grains (300 nm) by a weak and broad <441>_(Al) fibre. This is suggested to be associated with a modification of the predominant deformation mechanism, changing from dislocation slip towards grain boundary sliding at small grain size.