Production of AA6061 billets for thixoforging

The extruded AA6061 alloy recrystallized during heating to the semisolid state, producing nearly equiaxed polygonal grains with high angle boundaries. Melting started at triple junctions during subsequent isothermal heating and progressed along grain boundaries. The low melting point eutectic phase and the high angle grain boundaries introduced through recrystallization both promoted the grain boundary melting process. Complete grain boundary wetting, a perfectly cylindrical slug shape and an average grain size below 100 microns were obtained after 5 minutes at 640 degrees C for an extrusion ratio of 14:1.