Semi-solid extrusion of Al-10%Mg alloy with a non-dendritic structure

A simple mechanical stirring treatment during semi-continuous casting produced an Al-10%Mg alloy billet with a non-dendritic globular structure. Cylindrical specimens machined from the cast billets with and without stirring were extruded to bars at extrusion temperatures (T_e) ranging 763 to 843K and extrusion ratio (R_e) of 25 or 36. Even at lower R_e of 25, bars extruded from specimens with a dendrite structure (D-bar) had defuse surface cracks at the extrusion condition of higher T_e than 793K and ram speed (V_R) of 10mm/s. Specimens with a non-denditic structure could be extruded to bars (N-bar) without any surface cracks at the almost of extrusion conditions except for the lowest T_e =763K. Although at as-extruded conditions N-bars had a little lager elongations and higher strengths than those for D-bar, both values were much lower than 35% and 320MPa for the hot-extruded bar (H-bar). With decreasing of V_R to 2mm/s, the poor ductility and strength of N-bars were improved at the all T_eS. Especially at T_e of 783K, the mechanical property comparing to that for H-bar was found to be attainable.