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

摘要

High-energy milling process has been used to prepare Al72Cu17Fe11 and Al80Cu10Fe10 alloys. X-ray diffraction (XRD) and Mossbauer experiments were used to investigate the structural properties of the milled and annealed samples. Both alloys were milled for up to 150 h and Mossbauer spectroscopy shows that the milled Al72Cu17Fe11 alloy has no free alpha-Fe phase, while the milled Al80Cu10Fe10 has 12% 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 Al80Cu10Fe10 case, the annealing process leads to the formation of Al7Cu2Fe and Al13Fe4 phases, imbedded in an alpha-Al matrix, at 923 K. The measured hyperfine parameter values of the Al7Cu2Fe phase are delta = 0.14 mm s(-1) and Delta = 0.17 mm s(-1). For the Al23CuFe4 phase observed in the annealing temperatures up to 873 K, these are the parameter values delta = 0.25 mm s(-1) and Delta = 0.28 mm s(-1). For the Al72Cu17Fe11 case, the annealing process produces chemically disordered crystalline Al7Cu2Fe. The latter phase is stable at temperatures up to 923 K and it has isomer shift and average quadrupole splitting values of 0.19 nun s(-1) and 0.39 mm s(-1), respectively. [References: 11]