Structural properties and phase transformation in mechanically alloyed Al/Cu/Fe system

High-energy milling process has been used to prepare Al sub 72Cu sub 17Fe sub 11 and Al sub 80Cu sub 10Fe sub 10 alloys. X-ray diffraction (XRD) and Moessbauer experiments were used to investigate the structural properties of the milled and annealed samples. Both alloys were milled for up to 150 h and Moessbauer spectroscopy shows that the milled Al sub 72Cu sub 17Fe sub 11 alloy has no free alpha -Fe phase, while the milled Al sub 80Cu sub 10Fe sub 10 has 12 percent of alpha -Fe. XRD patterns indicate both compositions are disordered nanostructured phases. Differential scanning calorimetry measurements were performed to study structural phase transitions in the milled samples. The 150 h milled samples submitted to annealing process revealed that the alloys have distinct Fe environments, which seeds the formation of different crystalline phases. In the Al sub 80Cu sub 10Fe sub 10 case, the annealing process leads to the formation of Ald7Cud2Fe and Al sub 13Fed4 phases, imbedded in an alpha -Al matrix, at 923 K. The measured hyperfine parameter values of the Ald7Cud2Fe phase are delta = 0.14 mm s super -1 and Delta = 0.17 mm s super -1. For the Al sub 23CuFed4 phase observed in the annealing temperatures up to 873 K, these are the parameter values delta = 0.25 mm s super -1 and Delta = 0.28 mm s super -1. For the Al sub 72Cu sub 17Fe sub 11 case, the annealing process produces chemically disordered crystalline Ald7Cud2Fe. The latter phase is stable at temperatures up to 923 K and it has isomer shift and average quadrupole splitting values of 0.19 mm s super -1 and 0.39 mm s super -1, respectively.