Effect of complex alloying of Sc, Zr and Ti on the microstructure and mechanical properties of Al–5Mg alloys

The effect of complex alloying of Sc, Zr and Ti on the microstructure, recrystallization resistance and mechanical properties of Al–5Mg alloys is investigated. The complex alloying of Sc, Zr and Ti refines the grain size of Al–5Mg alloys to 62 μm, which is only half the size that of the alloy containing only Sc. The recrystallization temperature rises from 250 to about 450 °C. The yield strength increases from 135 to 250 MPa, which is close to the ultimate tensile strength of Al–5Mg. Ultimate tensile strength values above 390 MPa can be obtained, which are 40% larger than that of Al–5Mg. Though the uniform elongation of alloys decreases from 30 to 17%, the ductility is still excellent. The reason is that the complex alloying of Sc, Zr and Ti decreases the eutectic composition of Al–Al3Sc, which is favorable to the formation and stablization of primary and secondary complex particles such as Al3(Sc1−xZrx), Al3(Sc1−xTix). These particles not only increase the heterogeneous nucleation of the α-phase in melt but also effectively pin dislocations, grain boundaries or sub-boundaries.