Abstract
Friction Extrusion (FE) is a recently developed forming process that uses localized plastic deformation and high localized temperatures to refine the microstructure of the precursor alloy. FE has the potential to reduce thermal processing times and overall energy consumption. In the current study, conventional extrusion, and FE 6061 aluminum alloy (AA6061) rods were subjected to variable solution heat treatment times 0.9 to 3.6 kiloseconds (ks) to obtain modified T4 and T6 tempers. Microhardness testing and microstructural evaluation were performed to evaluate changes in mechanical properties; and to compare the response of conventional and friction-extruded materials to variations in the solution heat treatment times. The conventional aluminum samples required a solution treatment time of 1.8 ks (30 minutes) to achieve the typical ASM Handbook hardness value of 107 HV for the T6 temper. The friction-extruded, modified T6 tempered samples held for 0.9 ks (15 minutes) exhibited an average hardness of 109.2 HV. Therefore, the required thermal processing time was reduced by 50% (from 1.8 to 0.9ks). The nominal T4 temper hardness values were not achieved by the FE-processed or conventional samples for any of the hold times for the modified T4 temper thermal cycles. The modified T4 tempered FE-sample with a hold time of 3.6 ks (1 hour) reached a maximum hardness of 72 HV. However, the as-received AA6061 FE samples had an average hardness value of 74.5 HV, achieving the nominal hardness for an AA6061-T4 temper condition. Therefore, the FE process offers the potential for elimination of the requirement of a thermal cycle in order to achieve T4 temper properties for 6061 aluminum alloys.