| CUI Bo-shuai,WANG Jian-gang,ZHANG Xin,FENG Zhi-hao,YANG Guang,YUE Yan-fang,LI Jian-hui.Effect of Heat Treatment on Microstructures and Corrosion Properties of SLM AZ91D Magnesium Alloy[J],50(3):323-329, 365 |
| Effect of Heat Treatment on Microstructures and Corrosion Properties of SLM AZ91D Magnesium Alloy |
| Received:April 11, 2020 Revised:July 08, 2020 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2021.03.035 |
| KeyWord:AZ91D magnesium alloy selective laser melting solid solution treatment aging treatment microstructure corrosion resistance |
| Author | Institution |
| CUI Bo-shuai |
School of Materials Science and Engineering, Hebei University of Science and Technology, Shijiazhuang , China |
| WANG Jian-gang |
School of Materials Science and Engineering, Hebei University of Science and Technology, Shijiazhuang , China |
| ZHANG Xin |
School of Materials Science and Engineering, Hebei University of Science and Technology, Shijiazhuang , China |
| FENG Zhi-hao |
School of Materials Science and Engineering, Hebei University of Science and Technology, Shijiazhuang , China |
| YANG Guang |
School of Materials Science and Engineering, Hebei University of Science and Technology, Shijiazhuang , China |
| YUE Yan-fang |
School of Materials Science and Engineering, Hebei University of Science and Technology, Shijiazhuang , China |
| LI Jian-hui |
School of Materials Science and Engineering, Hebei University of Science and Technology, Shijiazhuang , China;Hebei Key Laboratory of Material Near-Net Forming Technology, Shijiazhuang , China;Hebei Engineering Laboratory of Aviation Lightweight Composite Materials and Processing Technology, Shijiazhuang , China |
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| Abstract: |
| This paper is devoted to investigate the effect of heat treatment on the microstructures and properties of resistance to corrosion of AZ91D magnesium alloy fabricated by Selective Laser Melting(SLM). The method adopted in this paper was to fabricate the samples of AZ91D magnesium alloy by SLM, and then solution treatment (T4) and solution-aging treatment (T6) were conducted, respectively. The microstructures and resistance to corrosion of AZ91D magnesium alloy samples with SLM, T4 solid solution and T6 solution-aging were tested and examined through metallographic microscope, scanning electron microscope, X-ray diffraction and electrochemical workstation. The results demonstarted that a substantial amount of the β-Mg17Al12 phases were dissolved in the matrix, and the size of grains was increased from 5 μm to 60 μm after being treated with solid solution at 420 ℃ for 6 hours. When the samples are heated to 200 ℃ for 2 hours after aging treatment, the β-Mg17Al12 phase precipitated from the matrix. Further, as the aging time being extended from 2 h to 6 h, the amount of precipitated phases were increased gradually. After being immersed in a solution of 3.5% NaCl for 120 hours, the corrosion pits on the surface of the samples were smaller, while larger corrosion pits appeared on T4 samples. In addition, the T6 samples demonstrated the most serious corrosion, with different sizes and depth of corrosion pits on the surface. The polarization curve of the samples showed that, Jcorr of the SLM sample was the smallest, with (1.889±0.2)×10–5 A/cm2, which also indicated the best resistance to corrosion. Jcorr of the samples treated by solution + aging for 2 hours was the largest, with (1.225±0.2)×10–4 A/cm2, indicating the worst corrosion resistance. As a result, regarding the resistance to corrosion in 3.5% NaCl solution, the order of corrosion resistance of different heat treatment samples is:the SLM sample >the T4 sample >the T6 sample. To summarize, the grain size of SLM samples was the finest and its resistance to corrosion was the best. The β-Mg17Al12 phases of SLM sample after solution treatment at 420 ℃ for 6 hours were dissolved substantially, and the size of the grains increased by an order of magnitude. After aged at 200 ℃ for 2 hours, the resistance to corrosion of samples are the weakest. When aging time was prolonged to 6 hours, however, the resistance to corrosion of the AZ91D alloys will be enhanced with the number of β-Mg17Al12 phases increased. |
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