- 學位論文
鋯元素改質對6061鋁合金機械性質與顯微組織之影響
Effect of Zirconium Modification on Microstructure and Mechanical Properties of 6061 Aluminum Alloy
摘要
本研究將針對A6061鋁合金分別添加0.2 wt.%、0.4 wt.%與1.2 wt.%的鋯元素，並以消失模鑄造法製成試樣後施以T6熱處理，再將處理完成的試樣進行成分分析、硬度試驗、微觀結構分析及機械性質測試，以瞭解不同鋯添加含量對各項性質的影響。 實驗結果發現，當固溶化處理時間固定時，隨著鋯添加量增加其所需的人工時效時間也會增加，且硬度會隨著時間的增加而提升。在顯微組織觀察中發現，添加鋯之後，晶粒尺寸會明顯地變小，但添加量超過0.4%時，晶粒細化之效果並無顯著的變化。而在機械性質上，添加鋯改質後，其性質也有所改變，拉伸強度在鋯添加量為0.2%時達到172.68 MPa最大值；而經T6熱處理後，則是在添加量為0.4%時達273.35 MPa。在硬度方面，未經熱處理之樣本中，在添加量為0.4%時則達到最大值69.6 HV；之而在經熱處理中的樣本中，以添加量為0.4%經30小時之時效硬化後達到最大值133.6 HV。在衝擊試驗方面，未經熱處理之樣本中，在添加量為0.2%時達到最大值686.0 J/m；在熱處理後則是以添加加量為0.4%時達到最大值741.13 J/m。以X光繞射儀分析之結果可看出，添加鋯後之析出相為Al3Zr4， 而在熱處理後產生的析出相主要為Al3Zr與Zr2Si。
並列摘要
Zirconium modified A6061 aluminum alloys were manufactured by lost foam casting process with 4 kinds of addition content, which are 0 wt.%, 0.2 wt.%, 0.4 wt.% and 1.2 wt.%. The solution treatment and artificial aging schedules were optimized to obtain superior mechanical properties and confirmed chemical composition within the crystals of the solid solution was uniform. Then, the effect of the modified alloys on the microstructure and mechanical properties were evaluated. The investigation says the necessary time for aging treatment increases while zirconium content increasing with fixed solution treatment time. The hardness also increases with time increasing. The microstructure indicates that grain size decreases after zirconium added but the effect of it doesn't change remarkably after zirconium content over 0.4 wt.%. Mechanical properties are also influenced after modified. The tensile stress reaches 172.68 MPa with 0.2% zirconium added; and it reaches 273.35 MPa after 0.4% zirconium added through T6 heat treatment. Besides, the hardness hits 69.6 HV with 0.4 wt.% before heat treatment; after T6 heat treatment, it hits 133.6 HV with 0.4 wt.% zirconium added. The impact stress approaches 686.0 J/m with 0.2 wt.% zirconium added before heat treatment, and it is raised to 741.13 J/m with 0.4 wt.% zirconium after T6 heat treatment. The X-ray diffraction results show that the main precipitation phase are Al3Zr4 with zirconium modified before heat treatment, Al3Zr and Zr2Si after heat treatment.