摘 要
本研究以A356 (Al-Si-Mg)系之鋁合金進行不同厚度鑄件低壓鑄造實驗，本實驗目的為探討不同厚度之試片鋁合金於實務低壓鑄造上的流動填充與氧化膜生成的條件與方式，透過調整鑄造參數，如低壓鑄造壓力、加壓時間、模具預熱溫度等來探討與機械性質關係，並輔以MAGMA 5.5鑄造模擬軟體互相驗證分析。
實驗得知低壓鑄件試片越厚，其機械性質較佳，原因為保壓時間與壓力充足得到完整的填充與樹狀晶枝狀間距得到補充。相對來說厚度2.8 mm的板件會因鋁湯充模時壓力過大，導致尾端鋁湯流動不穩定介面撞擊模壁造成浪捲、捲氣，將其帶進鋁液內部並向中間段補充，導致過多的氧化膜在試棒中間段產生使得機械性質不佳。
在低壓鑄件填充過程中，位在外側的板件入模速度大於位在內側的板件，入模速度影響了鋁湯充模噴濺的比例。噴濺屬於極為不穩定的液面流動，很容易波前先行通過卻並未完整填充，導致熔融鋁合金中間產生捲氣，或是過快流至試片尾端造成回流，產生大量的捲氣，使得介在物與氧化模的比例大增，影響A356低壓鑄件的機械性質表現。關鍵字：A356鋁合金、低壓鑄造、氧化膜
ABSTRACT
This study investigates the low-pressure die casting of A356 (Al-Si-Mg) series aluminum alloy with varying casting thicknesses. The primary objective is to explore the flow behavior and oxide film formation under practical casting conditions for specimens of different thicknesses. By adjusting casting parameters such as pressure, pressurization time, and mold preheating temperature, the study examines issues related to the stability of the filling front. MAGMA 5.5 casting simulation software is employed to validate and analyze the experimental results.
The experimental findings reveal that thicker castings exhibit better mechanical properties. This is attributed to sufficient pressure and holding time during solidification, which enable complete mold filling and compensate for dendritic spacing. In contrast, the 2.8 mm thick specimens show inferior mechanical properties due to unstable flow at the tail end during mold filling. Excessive pressure leads to turbulence and impingement of molten aluminum on the mold wall, causing wave formation and air entrapment. These defects introduce oxide films into the aluminum, particularly in the mid-section of the specimens.
Additionally, the filling speed is found to be higher in specimens located on the outer side of the mold compared to those on the inner side. This variation in filling speed increases the likelihood of splashing, an unstable flow behavior that often results in incomplete filling and gas entrapment. Rapid flow toward the specimen’s end followed by backflow further contributes to excessive entrapped air and oxide films, ultimately degrading the overall material quality and mechanical properties.Keywords：A356 Aluminum Alloy, Low-Pressure Die Casting, Oxide Film