鋁-矽合金具有良好加工性、耐蝕性佳、熱膨脹係數低等優點，因此在工業應用上相當廣泛。本研究選用的4832鋁合金為鋁-矽-銅-鎳-鎂合金，常用於汽車元件。然而元件在運轉狀態下常處於振動環境，因此振動破壞的阻抗是應用層面上必須面對的課題。在本研究中採用摩擦攪拌製程(Friction Stir Process, FSP)，探討材料在經過改質後，對於振動破壞阻抗能力的影響。4832鋁合金除了基地組織α-Al外，主要觀察到的晶出相為矽顆粒、δ(Al3CuNi)、τ1(Al9FeNi)、Q(Al5Cu2Mg8Si6)等。本材料在經過摩擦攪拌後，能夠讓矽顆粒及原本聚集的δ-τ1(-Q)分布變均勻，攪拌區的硬度也有提升。由振動試驗的數據顯示，在固定振動出力值以及固定試片初始偏移量的條件下，FSP材振動壽命優於O材及FSP-O材。將摩擦攪拌製程對於材料振動壽命的影響分成基地狀態以及晶出相分布型態兩方面進行探討：當基地狀態相近，而晶出相分布型態不同的條件比較(O材與FSP-O材)，改變晶出相型態對於材料振動壽命的提升效果有限；當基地狀態不同，而晶出相分布型態相近的條件比較(FSP材與FSP-O材)，摩擦攪拌強化基地對於振動壽命的提升效果較顯著。在此認為：摩擦攪拌製程對於材料振動壽命提升的主導因素為基地強化效應。
依改質區域取樣方向不同，針對FSPpara及FSPperp進行振動破壞裂紋解析，FSPpara的裂紋傳播與攪拌流紋相似，均呈弧狀樣貌。而FSPperp的裂紋則與攪拌流紋垂直，經過裂紋特徵定量化解析，FSPperp的振動壽命高於FSPpara，而裂紋轉折程度比較也呈現同樣情形，因此認為攪拌流紋排列方向(洋蔥環效應)影響振動裂紋傳播阻抗能力，為兩者振動壽命差異的原因。

Al-Si alloy is widely used for industrial applications due to its fine workability, high corrosion resistance, and low thermal expansion coefficient, etc. The 4832 aluminum alloy, which is Al-Si-Cu-Ni-Mg alloy system, is used for automobile components. However, the components are often in vibration condition while operating. Therefore, it is inevitable to deal with the issue of vibration fracture. In this study, friction stir process (FSP) is taken to discuss the effect upon vibration fracture resistance after modifying 4832 aluminum alloy.
In addition to α-Al matrix, there are four main segregate phases in 4832 aluminum alloy, including Si particles, δ(Al3CuNi), τ1(Al9FeNi) and Q(Al5Cu2Mg8Si6). After processing, Si particles and the agglomerate δ-τ1(-Q) are uniformly distributed, and the hardness of stirred zone also increased. According to the resultants of vibration tests, FSP sample exhibits better vibration life than O and FSP-O in the constant force condition and constant initial deflection condition. Investigation on the effect of friction stir process is divided into two aspects: the status of matrix and distribution condition of segregate phases. Comparing O with FSP-O: when the statuses of matrix are close, and let segregate phases distributed uniformly, the improvement of vibration life is limited. On the contrary, when we compare FSP sample with FSP-O: If the distribution situation of segregate phases are similar, the matrix intensified by friction stir process would be significant in enhancing vibration life. Therefore, the strengthening of matrix is considered the dominant factor in improving vibration life by friction stir process.
Based on the different sampling direction of modifying region, the vibration crack of FSPpara and FSPperp are analyzed respectively. The crack propagation of FSPpara is arc-like and parallel to the flow pattern caused by friction stir process. Crack propagation of FSPperp is perpendicular to the flow pattern.
The vibration life of FSPperp is better than FSPpara. According to the quantitative analysis about characteristic of vibration crack, the amplitude of crack reflection of FSPperp is also higher than FSPpara. It is thought that flow pattern (onion ring effect) could affect the resistance of crack propagation, which could be the reason for the variance of vibration life between FSPpara and FSPperp.

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