| 摘要: | 藉由光學顯微鏡(OM)、導電度(%IACS)、電子背向散射繞射(EBSD)、硝酸重量損失量測(ASTM G67)與機械性質量測，探討微量Zr (0.15wt%)、Sc (0.1wt%)與退火溫度，對AA5383（Al-5Mg-0.7Mn）合金之再結晶、抗敏化腐蝕、與機械與性質之影響。結果顯示，均質化過程中，因含微量Mn、Zr 與Sc 之合金，於晶粒內分別析出細小之MnAl4、Al3Zr與Al3Sc散佈相顆粒，有效阻礙再結晶、及晶粒成長，導致晶粒細化、及細晶強化；另外，微量Zr、Sc的添加，可提升合金之強度，其中又以退火溫度250℃時含Sc之合金強化效果最為顯著。低溫（250℃）退火時，合金發生部分再結晶，大部分仍屬織狀微結構，經敏化處理後，β相(Mg2Al3)會析出於晶界和次晶界上，此時合金具有較佳之抗敏化腐蝕能力，且因含Zr與Sc之合金，再結晶比例較含Mn合金低，所以含Zr與Sc之合金具有較佳耐腐蝕。當高溫（≥300℃）下退火，合金幾乎已經完全再結晶，導致抗敏化腐蝕能力的下降，晶粒愈細，抗蝕性愈低，此時，以含Mn合金有最佳之抗敏化腐蝕能力，含Sc合金則最低。當合金於高溫退火導致晶粒成長時，可略提升合金之抗敏化腐蝕能力。;This study used microstructure observation, electrical conductivity (%IACS), electron backscatter diffraction (EBSD), electron microscope (SEM), nitric acid corrosion weight loss test, tensile test and hardness test (HRF), etc., to discuss the effects of Zr (0.15wt%)、Sc (0.1wt%), and annealing temperature on the recrystallization, corrosion and mechanical properties of Al-5Mg-0.7Mn alloy.
The results showed that the alloy containing minor of Zr (0.15wt%) and Sc (0.1wt%) will precipitate Al3Zr and Al3Sc dispersed phase particles in the grains during the homogenization process, which can increase the recrystallization temperature of the alloy and effectively. In addition, the addition of trace amounts of Zr and Sc can improve the strength of the alloy, and the strengthening effect of the alloy containing Sc is the most significant when the annealing temperature is 250 °C. When annealed at a low temperature (250 °C), the alloy is partially recrystallized, and most of it still has a textured microstructure. After sensitization treatment, the β(Mg2Al3) phase will precipitate discontinuously on the grain boundary and subgrain boundary. Therefore, the alloy has excellent resistance to sensitized corrosion. Because the recrystallization ratio of the alloy containing Zr and Sc is lower than that of the alloy containing Mn. The alloy containing Zr and Sc has better corrosion resistance.
When annealed at high temperature (≥300°C), the alloy is almost completely recrystallized, and the β phase will continuously precipitate on the grain boundary, resulting in a decrease in the alloy′s resistance to sensitized corrosion. The finer the grains, the lower the corrosion resistance. Therefore, the corrosion resistance of Mn-containing alloys is the best. The sensitized corrosion resistance of the alloy is slightly improved when grain growth is induced by annealing at a high temperaturessure. |
