- 期刊
鋁合金A356熱處理及破裂靱性之研究
On Heat Treatments and Fracture Toughness of Aluminum Alloy A356
摘要
材料破裂靱性之求取，應用於設計上，可避免工程零組件及結構產生突發性之破壞；提高材料使用之壽命及安全性。矽鎂系鑄鋁合金在鑄造狀態下，組織中含有多量顆粒大、形狀尖銳之矽鎂化合物，以致機械性質大幅降低，一般均施以析出硬化熱處理，達到強化分析出效果。合金細化劑之添加，可使結晶粒細化，更加強機械性質之提升。細化劑一般均使用Al-Ti-B合金；而本研究則着重添加鍶（Sr）元素對鑄鋁合金A356之影響，並探討熱處理與金相組織、機械性質及破裂靱性之關係，同時並做電子顯微鏡及X-光繞射分析。結果發現，熱處理得當之A356鑄鋁合金，其破裂靱性K_(10)值可達21〜30M Pa．m^(1/2)，與擠製鋁材之K_(10)值雷同，而一般之機械性質，如：抗拉強度、延伸率、硬度及衝擊值等亦均佳。實驗結果並顯示，高溫短時間（560℃，3hrs）的固溶化熱處理，配以較高溫（180℃，4hrs）的時效化熱處理，所得之機械性質，並不亞於傳統熱處理（固溶化540℃，9hrs；時效化160℃，10hrs）之結果，且可有節省能源及工時之優點。
關鍵字
無資料並列摘要
The study of fracture mechanics of a material and its application to the design of machine parts or structures can prevent the occurrence of unpredicted catastrophic failure. In the as-cast condition, AI-Si-Mg alloys contains substantial quantity of large and sharp Mg-Si compound particles in the matrix. This causes significant decrease in mechanical properties. Hence, precipitation hardening heat treatment is usually applied to these alloys. Addition of modifiers can refine the grain size, and further increase the mechanical properties. The most often used modifier for cast aluminum is AI-Ti-B alloys. In this research, the addition of strontium and its effects on the cast aluminum alloy A356 was studied. The relationship between heat treatment, microstructure, mechanical properties, and fracture toughness were investigated. SEM fractography and X-ray diffractometry were also applied to study the fracture morphology and the micro-constituents of the material. The fracture toughness K_(10) of cast aluminum alloy A356 with proper heat treatment were found to be in the range of 21~30 MPa．m^(1/2), which is comparable to the wrought AI-Si-Mg alloys. The general mechanical properties, e. g. tensile strength, elongation, hardness, and impact toughness were all satisfactory as well. It was also found that high temperature solution treatment (560°C, 3 hours) accompanied with high temperature aging treatment (180°C, 4 hours) resulted in equivalent properties as that of the traditional treatment (540°C, 9hours solution traetment, 150~160°C, 10 hours aging treatment). This can contribute to the overall saving in the labor-time and energy.