Corrosion fatigue of magnesium alloys

To study the fatigue life of extruded AZ31 (3%A1, l%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 and NaCl-based solutions, corrosion fatigue tests were carried out using a rotating beam type fatigue machine. For the analysis of the corrosion fatigue behavior of Mg alloys in different environments, fitted N_sol/N_air ratio considered as a relative corrosion fatigue life is used. Here N_sol and N_air are the numbers of cycles to failure in the solution and in air, respectively. An extruded ZK60 alloy shows very high fatigue and corrosion fatigue properties in comparison with other alloys. However, ZK60 shows the lowest values of the relative fatigue life (N_sol/N_air∼10^-3-10^-2) compared to that for AM50 and AZ31 alloys (N_sol/N_air ∼10^-2 - 10^-2). Generally, extruded alloys in comparison to earlier studied die-cast alloys show a higher sensitivity to the action of NaCl; however, under the same stress, their corrosion fatigue life is significantly longer than that of die-cast alloys.