Abstract
Abstract The effects of the single and compound addition of rare earth Gd and Er on corrosion resistance and residual strength of as-cast AM50 magnesium alloy were studied using XRD, SEM, EDS, the weightlessness test, electrochemistry method, and tensile test. The results of XRD and SEM showed that Al3Er, Al2Gd3, and Al–Mn–Gd(Er) phases appeared in the alloy structure after the addition of rare earth Er and Gd. The results from the weightlessness test and Tafel curves show that the corrosion resistance of the modified composite rare earth was improved. Stress concentration caused by a corrosion pit is the direct cause of the tensile samples after corrosion. The corrosion residual strength of modified composite rare earth specimens is better than that of modified single rare earth samples. Fracture analysis indicates that the addition of rare earth elements did not change the fracture mechanism of the alloy, and the fracture was still the cleavage fracture.
Highlights
Mg alloys, as the lightest metal structures, are widely applied in the automotive and aerospace industries owing to their ultra-high specific strength and specific stiffness, Among different material performance improvement methods, alloying is frequently used, alloying with rare earth elements (REEs) [5]
The structures, elements, and fractures of the specimens were observed under a scanning electron microscope (SEM) (ZEISS EVO18, Germany) equipped with an energy dispersive spectrometer (EDS)
The results of the original mechanical properties showed that the non-eroded strength did not differ largely among the three alloys, but the presence of Er and Gd improved the corrosion resistance and thereby increased the residual strength of AM50ErGd
Summary
As the lightest metal structures, are widely applied in the automotive and aerospace industries owing to their ultra-high specific strength and specific stiffness, Among different material performance improvement methods, alloying is frequently used, alloying with rare earth elements (REEs) [5]. Mg and REEs are both tightly arranged hexagonal structures, and the differences in atomic radius between them are within ±15%. Because of their similar electronegativity, REEs are all highly solid-soluble in Mg alloys. REE Gd has an electron arrangement of 4f75d16s2, and a semi-full 4f electron orbit, forming a stable electron structure [9]. Because of the very large atomic radius and since the outermost-layer s electron and the single-layer 5d electron are prone to loss, Gd can become Gd3+ with high chemical activity. The Er atom has an outermost valence electron status of 4f125d16s2 and belongs to trivalent REEs [11]
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