AUTHOR=Jiang Quantong , Lu Dongzhu , Liu Chang , Liu Nazhen , Hou Baorong 

TITLE=The Pilling-Bedworth Ratio of Oxides Formed From the Precipitated Phases in Magnesium Alloys

JOURNAL=Frontiers in Materials

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2021.761052

DOI=10.3389/fmats.2021.761052

ISSN=2296-8016

ABSTRACT=<p>The Pilling-Bedworth ratio of oxides preferentially formed from the precipitated phases in magnesium alloys were calculated. The results showed that the PBR value of Nd<sub>2</sub>O<sub>3</sub> preferentially formed from Mg<sub>12</sub>Nd was 1.0584, and the PBR value of Y<sub>2</sub>O<sub>3</sub> preferentially formed from Mg<sub>24</sub>Y<sub>5</sub> was 1.1923. Both the Nd<sub>2</sub>O<sub>3</sub> and Y<sub>2</sub>O<sub>3</sub> would provide a good protection to the Mg matrix. The Gd<sub>2</sub>O<sub>3</sub> preferentially formed from Mg<sub>3</sub>Gd, whereas the MgO preferentially formed from MgNi<sub>2</sub>. The PBR value of these two oxides were both larger than 2. The corresponding oxides formed from the common precipitated phases Mg<sub>17</sub>Al<sub>12</sub>, MgZn<sub>2</sub>, MgCu<sub>2</sub>, Mg<sub>2</sub>Ca, Mg<sub>12</sub>Ce, and MgAg were all less than 1. The oxide films formed on surfaces of pure Mg and Mg-xY (<italic>x</italic> = 3, 5, 7 wt.%) alloys at high temperatures were analyzed. The results showed that the oxide films were composed of a Y<sub>2</sub>O<sub>3</sub>/MgO outer layer and an inner layer rich with Y<sub>2</sub>O<sub>3</sub>. The formation of Y<sub>2</sub>O<sub>3</sub> was mainly caused by the oxidation of Mg<sub>24</sub>Y<sub>5</sub>. The more Y<sub>2</sub>O<sub>3</sub> existed in the composite oxidation film, the better corrosion resistance of the Mg-Y samples.</p>