The oxidation behaviour of an AZ91D magnesium alloy at high temperatures

Native Oxide Films on AZ31 and AZ61 Commercial Magnesium Alloys – Corrosion Behaviour, Effect on Isothermal Oxidation and Sol–gel Thin Film Formation

“…As Czerwinski [26] reported, the maximum oxide thickness achieved during heating (as converted from weight gain data) was equal to 64 nanometres for 197°C. This film thickness is too small to produce a sufficient signal for conventional materials characterisation techniques (Optical microscopy, SEM/EDX, XRD or TEM) [27].…”

“…From XPS analysis of oxide film thickness, it is observed that this value in the AZ61-P specimen is some 2 nm thicker than on the AZ31-P specimen (Figure 5a). The differences in film thickness among the two alloys are probably related with the degree of perfection of the oxide films and differences in diffusion rate of the reaction products [13], [26] and [58]. The higher film thickness values obtained with the AZ61 alloys, which contain more Al than AZ31 alloy, may be related to the heterogeneous structure associated with the β-precipitation phase located in the boundaries (Figure 3b).…”

“…It will be observed From XPS analysis of oxide film thickness, it is observed that this value in the AZ61-P specimen is some 2 nm thicker than on the AZ31-P specimen (Figure 5a). The differences in film thickness among the two alloys are probably related with the degree of perfection of the oxide films and differences in diffusion rate of the reaction products [13], [26] and [58]. The higher film thickness values obtained with the AZ61 alloys, which contain more Al than In the literature about the corrosion of magnesium alloys, it is normal to associate the diameter of the capacitive loop in the HF/MF region with the charge transfer resistance (RCT) of the corrosion process [9,59,60] value which is inversely related to the corrosion current (icorr) through the well-known Stern-Geary equation [61]:…”

“…Czerwinski [26] studied the oxidation behaviour of AZ91D Mg alloy at different temperatures. His results showed that AZ91D exhibited protective oxidation only at a temperature of 197°C, while at higher temperatures, the behaviour was non-protective and associated with the formation of oxide nodules and their coalescence into a loose fine-grained structure.…”

Diagnosis and Analysis of Oxide Films in Cast Magnesium Alloys by Ultrasonic-Vibration Treatment

“…Spinel has a low free energy so that is often forms at the interface of the matrix and magnesia or intermetallic compound. 1,[4][5][6] These oxide films can also serve as nucleation sites for the formation of pores or inclusions in cast magnesium alloys, which of cause accelerates fatigue crack propagation eventually leading to fatigue failure. 7) In other words an oxide film is extremely harmful to the quality of cast magnesium.…”