| 摘要: | 本研究針對2024鋁合金以及7046鋁合金進行探討。探討不同合金成份、均質化處理(均質化溫度、冷卻速率)、擠製前之預熱溫度，對2024、7046鋁合金擠型性和機械性質的影響。 實驗以擠製時造成的最大壓力值以及表面品質來評估其擠型性，藉由DSC熱差分析儀分析材料擠出後以及經過時效後基地內析出狀態，利用光學顯微鏡(OM)、穿透式電子顯微鏡(TEM)觀察合金內再結晶情形以及析出強化相分布情形，以掃描式電子顯微鏡(SEM)觀察材料拉伸、衝擊斷裂面。 2024鋁合金最佳的均質化條件為溫度520℃時間10小時，可將鑄造時產生的偏析以及共晶相消除。雖然擠製前預熱溫度越高，擠製後的固溶程度越大，但是對2024鋁合金而言，預熱溫度越高，則越容易造成表面龜裂的現象，因此預熱溫度不可過高。高含量Cu、Mg的2024合金具有相當的強度，但是其衝擊韌性卻是最低的，而低含量Cu、Mg合金的強度雖低，但是卻有較高的衝擊韌性。 7046鋁合金最佳的均質化條件為溫度470℃時間24小時。擠製後造成基地的固溶度隨均質化溫度、預熱溫度的提高而增加，可得到較高的硬度值；但就強度而言，均質化溫度及預熱溫度越高，卻造成再結晶組織粗大，反而使強度下降。Zn含量改變對7046合金而言，對機械性質似乎沒有太大的影響，而Mg含量的改變就有明顯影響：7046-LMg雖然強度最低，但衝擊韌性卻是最高的。 The effects of the alloy compositions, homogenization and re-heating temperatures on the extrudability and mechanical properties of 2024 and 7046 aluminum alloys were investigated. In this study, the extrudability was evaluated with the maximum extrusion pressure and the surface quality of the extruded products. The mechanical properties were investigated using tensile, impact and hardness tests. Differential scanning calorimetry (DSC) in conjunction with transmission electron microscopy (TEM) were used to characterize the matrix precipitates of the alloys. The microstructural and fractured characterization were examined by optical and scanning electron microscopy (SEM). For the 2024 aluminum alloy, the homogenization treatment with 520℃ for 10h can effectively eliminate the segregation and eutectic phase of the cast alloy. The degree of the solute supersaturation was increased with the reheating temperatures, but too high reheating temperature would also cause a higher susceptibility to hot cracking during extrusion. The 2024 alloy with high Cu and Mg contents revealed a considerately tensile strength, but the lowest impact toughness; In contrast, the alloy with low Cu and Mg contents revealed lower strength but higher impact toughness. The existence of eutectic phase was found to significantly influence the toughness property but slightly on the tensile strength. For the 7046 aluminum alloy, the optimum homogenization treatment examined was 470℃ for 24h. The degree of the solute supersaturation of the alloy after extrusion was increased with increasing the homogenization and reheating temperatures. The results indicated that the extrudability was increased with extrusion temperature. Higher hardness values would be obtained by increasing homogenization and reheating temperatures, however, the tensile strength was opposite to the hardness measurements. This strength decay was primarily due to the coarsening of the recrystallized structure. Moreover, the mechanical properties were significantly affected by the variation of the magnesium content, but slightly affected by the zinc content. The 7046 alloy with low Mg content exhibited the lowest strength but highest impact toughness. |
