Study of fatigue crack growth behaviour of Al-Mg and Al-Mg-Sc-Zr alloys

Fatigue crack growth behaviour of Al-Mg and Al-Mg-Sc-Zr alloys is studied under different orientations and stress ratios. The microstructures and the fracture morphologies of each alloy are observed. For both alloys, they have Brass, S and Goss texture; while only Al-Mg alloy has Cube texture which indicates recrystallisation; as fatigue crack propagated, intergranular fracture transformed into transgranular fracture accompanied with gradually coarser crack surfaces. Al-Mg alloy is featured by large recrystallised grain, favourable plasticity, rougher crack surfaces, and with relatively strong crack growth resistance before rapid growth. While Al-Mg-Sc-Zr alloy with small grain size and relatively smoother crack surfaces, shown cyclic stability at higher Δ K level.