本文探討A319.0鑄鋁合金中添加微量鈹與不同固溶溫度對富鐵相、矽粒子、富銅相之形態以及機械性質之影響。實驗結果顯示，鈹之添加不僅提昇Al-Al2Cu共晶溫度，並可以使部份針狀富鐵相(β-FeSiAl5)轉換為較無害之中文字形富鐵相(α-Fe2SiAl8)，同時減低針狀富鐵相之尺寸與數量。較細小針狀富鐵相在固溶處理(>500℃)時有助於溶解、分裂之進行，更高的固溶溫度則加速溶解與分裂之行為。然而，若固溶溫度超過了Al-Al2Cu共晶溫度，將會有Al-Al2Cu共晶熔化之液相產生，此液相在淬火時會形成非結構性組織，反而會降低材料之機械性質。 A319.0鑄鋁合金之破裂行為受富鐵相、富銅相以及矽粒子之形態和大小所影響，由破裂韌性試片之斷裂面金相分析顯示，破裂起始極易發生在針狀富鐵相之脆斷或針狀富鐵相與基地分離所形成之裂紋。結合鈹之添加與高溫固溶處理，可以降低針狀富鐵相之脆斷、及與基地分離之機會，因而，有效的提昇材料之強度、延性與破裂韌性。 The effects of beryllium (Be) and solution temperature on the morphologies of iron intermetallics, silicon particles and copper intermetallics that relates to the mechanical properties of A319.0 alloys are investigated. The experimental results indicate that adding Be to the alloy can raise the Al-Al2Cu eutectic melting temperature, change some platelet-like shape (β-Al5FeSi) of iron intermetallics to comparatively harmless Chinese-script morphologies (α-Al8Fe2Si), and reduce the amount and average length of β-Al5FeSi platelets. During high temperature solution treatment (>500℃), the thinner and smaller theβ-Al5FeSi platelets are, the faster they dissolve and fragment. However, where the solution temperature exceeds the Al-Al2Cu eutectic melting point, the Al-Al2Cu eutectic melts and results in an ultra-fine eutectic phase on quenching, which deteriorates mechanical properties. The fracture behavior of A319 alloy is affected by the morphologies of the iron intermetallics, silicon particles and copper intermetallics. Fractographic analysis of tested compact tension specimens reveals that the fracture processes are mainly initiated by void nucleation at β-Al5FeSi platelets as a result of their cracking and decohesion from the matrix. Adding Be to the A319.0 alloy and optimizing the solution temperature can significantly decrease the number of fracture-initiation sites of β-Al5FeSi platelets and improve the tensile properties and fracture toughness.
