Mechanical properties and microstructure of aluminum alloy 2618 with Al3(Sc, Zr) phases

The tensile properties of a 2618 (Al–Cu–Mg–Fe–Ni) alloy containing scandium and zirconium were measured at 293, 473, 523 and 573 K to study the temperature influences on the experimental alloys. The microstructure was observed by using optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the addition of scandium and zirconium to 2618 alloy resulted in a primary Al3(Sc, Zr) phase. Such phase could refine the alloy grains because it acted as a core of heterogeneous crystallization during solidification. The secondary Al3(Sc, Zr) particles that precipitated from the α(Al) solid solution were fully coherent with the matrix and had an obvious precipitation hardening effect. They also made the S′ phase precipitate more homogeneously. The strengths of the 2618 alloy with Al3(Sc, Zr) phases increased at both ambient and elevated temperatures, without a decrease of ductility.