Microstructures of erbium modified aluminum-copper alloys

E. Berghof-Hasselbächer, P.J. Masset, L. Zhang, L. Liu, Z. Jin, G. Schmidt, M.C. Galetz, M. Schütze

Alloying with rare earth metals improves to the mechanical properties and corrosion resistance of aluminum base alloys at high temperatures. The rare earth metal erbiummay be used for grain refinement. Within a project of computer-aided alloy development based on the CALPHAD (CALculation of PHAse Diagrams) method variousalloys were melted on the Al-rich side of the ternary system Al-Cu-Er under argon atmosphere and their microstructures were characterized in the as-cast state or afterlong-term isothermal annealing (400°C/960 hours) by means of different investigation techniques. As a result, the phases Fcc (Al), t1-Al8Cu4Er, q-CuAl2, h-CuAl, and Al3Erwere identified, their compositions and fractions were quantified, and their hardnesses were determined. The experimental obtained microstructures agree very wellwith the calculated solidification behaviors of the cast alloys. The knowledge gained from this work about the phase compositions and microstructures can also be utilizedfor the fine optimization of the phase diagram.

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