Al - Mg - Cu based alloys and pure Al processed by high pressure torsion : the influence of alloying additions on strengthening

The influence of alloying additions on strengthening of high pressure torsion (HPT) processed alloys was investigated using commercially pure Al (Al-1050 alloy) and five Al-(1-3)Mg-(0-4)Cu alloys (in wt%). Microhardness was measured on cross sections. For Al-1050 the microhardness reaches a peak at an effective strain of about 3 and subsequently decreases. The microhardness of Al-Mg-Cu alloys increases strongly and continuously with increasing equivalent strain. This workhardening rate is enhanced by increasing Mg content over the entire range of strain. Furthermore, the workhardening rates were higher in Cu-free and low Cu-containing (≤ 0.4%) Al-Mg alloys as compared to high Cucontaining Al-Mg alloy at strains less than 3. The results indicate that dislocation-solute and dislocation-cluster interactions play an important role in strengthening.