Effect of minor Zr and stabilizing treatment on the corrosion and mechanical properties of AA5383 alloys
| Autor: | Chun-Hung Yen, 顏俊宏 |
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| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 This study explored the effects of zirconium and stabilization on the mechanical and corrosion properties of AA5383 alloys by microstructural observations, ASTM G67 nitric acid corrosion weight loss tests, hard corrosion, and mechanical property tests (hardness, drawing). The results show that the annealing temperature is the main factor to change the microstructure and mechanical strength of Al-Mg alloy. Annealing temperature is lower than 250°c for recovery structure, annealing temperature is higher than 250°c and begins to change into partial recrystallization structure. Among them, the hardness and tensile strength show a direct relationship with each other. The results of NAMLT and SSRT tests show that the β-phase corrosion morphology is affected by the annealing structure. Among them, the poorly-arranged microstructure and recrystallization structure make the β phase precipitate along the grain boundaries after sensitization of the alloy, and the grains exhibit exfoliation corrosion after sensitization and corrosion. In addition, when aluminum-magnesium alloy is annealed at 200-250°C, the composition phase changes from α+β to α-phase, and after sensitization, the β-phase precipitates more dispersed and less continuous, so the intergranular corrosion susceptibility is increased. And stress corrosion sensitivity is the lowest. Aluminum-magnesium alloy containing trace amounts of zirconium contains Al3Zr particles, and has fine-grained strengthening and dispersion strengthening effects, which makes the hardness higher than that of alloys without added zirconium, and effectively inhibits differential row slip and grain growth, and raises the recrystallization temperature of alloys. However, in the chill roll and recovery stage, the coarsening of Al3Zr particles becomes a heterogeneous nucleation site due to the differential structure, so that the β phase is precipitated along the grain boundary, and the Al3Zr particles are easily precipitated and the corrosion resistance of the material deteriorates. After the annealing treatment at a relatively high temperature of 280°C, the aluminum-magnesium alloy containing Zr has the effect of inhibiting recrystallization, and the micro-fibrous structure of the microstructure and the partially recrystallized structure coexist, and the corrosion resistance of the alloy is superior to that of the Zr-free alloy. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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