The Investigation of Eutectic Structure of Al-Fe-Cr Ternary System in the Al-rich Corner
This research work presents a systematic and comprehensive investigation of Al-Fe-Cr alloys at sub-solidus temperature within the Al-rich corner of the ternary phase diagram. Due to the lack of detailed information on phase equilibria in this region, ten different alloys within the composition range of 96.6 - 99.6 at.% Al were studied, both in their as-cast and annealed states. Microstructural characterizations of the alloys were done using SEM, XRD, EMPA and optical microscopy techniques. Meanwhile, their thermal behavior was performed using DTA technique.
Based on the experimental results, the partial Liquidus and Solidus projections were drawn. The nature of the phase equilibria and invariant reactions observed among the phases [<Al>, θ<Al13Cr2>, η<Al11Cr2>, <Al13Fe4> and H<Al82.5Cr11.5Fe6>] were different from that recently reported in the literature. Also, the result of the mechanical properties, as revealed by Brinell Hardness Test, showed that eutectic Alloy 7 (97.63Al - 0.17Cr - 2.20Fe)at.% has the highest hardness value of approximately 456.33MPa (as cast) and 275.58MPa (annealed), as when compared with other investigated alloys. Conclusively, the research findings will help in the subsequent development of eutectic Al-Fe-Cr alloys with excellent mechanical properties especially for use in the Aerospace industry. The experimental results will also serve as important inputs in the future thermodynamic modelling of this system.