| CHENG Dan-dan,YAO Huai,JIAO Yan-ke,XIONG Yi.Microstructure Evolution and Degradation Mechanism of As-extruded Mg-1.8Zn-0.5Zr-xGd (0≤x≤2.5wt.%) Bio-magnesium Alloys[J],51(7):195-206 |
| Microstructure Evolution and Degradation Mechanism of As-extruded Mg-1.8Zn-0.5Zr-xGd (0≤x≤2.5wt.%) Bio-magnesium Alloys |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.07.019 |
| KeyWord:magnesium alloy extrusion microstructure corrosion resistance |
| Author | Institution |
| CHENG Dan-dan |
Zhengzhou Vocational College of Finance and Taxation, Zhengzhou , China |
| YAO Huai |
School of Materials Science and Engineering, Henan University of Science and Technology, Henan Luoyang , China |
| JIAO Yan-ke |
School of Materials Science and Engineering, Henan University of Science and Technology, Henan Luoyang , China |
| XIONG Yi |
School of Materials Science and Engineering, Henan University of Science and Technology, Henan Luoyang , China |
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| Abstract: |
| The work aims to improve the corrosion resistance of Mg-0.5Zr-1.8Zn-xGd (x=0, 0.5wt.%, 1.0wt.%, 1.5wt.%, 2.0wt.%, 2.5wt.%) bio-magnesium alloys in the simulated body fluid. Mg-0.5Zr-1.8Zn-xGd alloys are treated by solid-solution and extrusion to get uniform fine microstructure. The grain morphologies, texture, phase compositions and surface corrosion morphology are analyzed by OM, SEM, EDS, EBSD and TEM. The corrosion resistance of the alloysis characterized by electrochemical curves and corrosion tests. The surface elements with chemical states before and after corrosion of Mg-0.5Zr-1.8Zn-xGd alloys are texted by XPS. The results show that when the extrusion temperature and extrusion ratio are 360 ℃ and 7.7, the alloy undergoes relatively complete dynamic recrystallization. With the increase of Gd content, the grain size gradually decreases, and the corrosion resistance first increases and then decreases. The alloy with a Gd content of 1.5wt.% has a good corrosion resistance, and the corrosion rate is about 0.447 mm/a. When the Gd content is 1.5wt.%, a small amount of nano-sized round rod-shaped (Mg,Zn)3Gd phase particles and nano-sized elliptical spherical Mg2Zn11 phase particles are precipitated in the alloy, and with the increase of Gd content, the number and volume fraction of second phase particles in the alloy gradually increase. The corrosion process of Mg-0.5Zr-1.8Zn-1.5Gd alloy is divided into three stages with the increase of soaking time within 120 h. The formation and thickening of Mg(OH)2 corrosion products on the alloy surface leads to a rapid decrease in the corrosion rate at the initial stage. The subsequent formation and thickening of compact Mg(OH)2, (Ca, Mg)3(PO4)2 and Ca10(PO4)6(OH)2 corrosion products lead to a slow decrease in corrosion rate. Finally, the formation and dissolution of corrosion products reach a dynamic equilibrium, resulting in a stable corrosion rate.Extrusion deformation can significantly enhance the corrosion resistance of Mg-0.5Zr-1.8Zn-xGd alloys by effectively refining the grains with homogenize and disperse precipitate distribution. |
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