Grain Refinement of 6061 Al Alloy by the Modified Strain-Induced Melt- Activated(SIMA) Process for Semi-Solid Processing

The dynamic process of fine grain evolution of 6061 aluminum alloy during modified strain-induced, melt-activated (SIMA) process was studied. The modified SIMA process employed casting, two stage homogenization, warm multi-forging, and recrystallization and partial melting (RAP). Multi-forging was carried out at a strain rate of 9x10-3 s-1 to accumulate high strains, with decreasing temperature from 250 to 200 °C. The alloy multi-forged with the accumulated strain of about 12 and RAP at 640 °C for 10 min exhibited the uniform equiaxed recrystallized grain structure. Accordingly, it was evident that multi-forging was very effective on grain refinement and grain size uniformity. The present modified SIMA process was discussed as an alternative thermo-mechanical processing for preparing the alloys with fine grained structure for semi solid processing.