Corrosion fatigue of extruded magnesium alloys

Corrosion fatigue tests were carried out on extruded AZ31 (3% Al, 1% Zn, 0.3% Mn, Mg—the rest), AM50 (5% Al, 0.4% Mn, Mg—the rest) and ZK60 (5% Zn, 0.5% Zr, Mg—the rest) Mg alloys in air, NaCl-based and borate solutions. Nsol/Nair ratios (the relative fatigue life) were used for the analysis of the corrosion fatigue behavior of Mg alloys in various environments, where Nsol and Nair are the numbers of cycles to failure in the solution and in air, respectively. Extruded ZK60 alloy reveals very high fatigue and corrosion fatigue properties in comparison with other alloys. However, it has the lowest relative fatigue life (Nsol/Nair ∼10−3–10−2) or the highest sensitivity to the action of NaCl-based solutions in comparison with that of AM50 and AZ31 alloys (Nsol/Nair ∼10−2–10−1). Under the same stress, the corrosion fatigue life of extruded alloys is significantly longer than that of die-cast alloys (Nsol for extruded AM50 in NaCl is two to three times longer than that of die-cast AM50).