Development of High-Strength Al-Cu-Mg Alloy by Combined Application of High-Pressure Torsion and Aging Treatment

Solution treated Al-Cu -Mg alloys with three different compositions were subjected to high-pressure torsion (HPT) for 1 to 50 turns, and then aged at 423 K. By conducting HPT process, the hardness of the three alloys significantly increased after 50 turns, and the average grain sizes were refined to 130-140 nm. After aging treatment, the hardness was further increased to 271 HV, 288 HV and 273 HV in the peak aging condition for the Al-4Cu-1.5Mg, Al-4Cu-3Mg and Al-5Cu-3Mg (in mass%) alloys, respectively. The contribution of several strengthening mechanisms was quantitatively evaluated in terms of grain boundary hardening, dislocation hardening, solid solution hardening and cluster/ precipitation hardening. It is shown from the quantitative evaluation that simultaneous strengthening due to grain refinement and nanoscale precipitates is successfully achieved by combined application of HPT process and subsequent aging treatment.