特殊固溶處理與後時效對ADC12鋁合金機械性質之影響

Effect of Special Solid Solutioning and Aging Treatments on Mechanical Properties of ADC12 Al Alloy

鍾佑祥(Y. X. Zhong) ； 許哲維(C. W. Hsu) ； 楊智富(C. F. Yang) ； 陳俊沐(C. M. Chen) ； 邱垂泓(C. H. Chiu) ； 曾發培(F. P. Tseng)

《鑄造工程學刊》 45卷2期 (2019/06) Pp. 27-34

摘要

壓鑄用ADC12鋁合金應用十分廣泛，但因其鑄件含有大量共晶矽、富銅晶出相與富鐵相等脆性組織，故其製品往往只能作為外觀件，若作為結構件則有延性與韌性不足之問題。本研究以成分微調搭配特殊熱處理方式來進行改善，共配製三種ADC12系列鋁合金，包括ADC12（10Si）、ADC12（11Si）兩種商用鋁合金以及改良型合金ADC12（+），並搭特殊固溶處理及後時效析出強化來提升壓鑄用ADC12鋁合金之機械性質。實驗結果顯示，兩種商用ADC12鋁合金在鑄造狀態下，其組織包括淺灰色之樹枝狀初晶α（Al）相以及樹枝狀晶間深灰色的共晶組織（共晶α+Si）；由於高壓鑄造件之冷凝速度快，其非平衡式凝固造成鑄件之初晶α相體積比增加。而添加0.02%Sr、0.3%Cr及0.3%Zr之ADC12（+）鋁合金顯現最佳之微觀組織與機械性質。所添加微量調質劑（Sr）可將合金內片狀共晶矽轉化為微細纖維狀，中和劑（Cr）將大片狀β-Al_5FeSi富鐵相轉化為細小塊狀之α-Al_(13)（Fe,Cr）_4Si_4，使合金之延伸率得以提升。機械性質數據顯示，不論商用或改良型之ADC12（+）鋁合金，在鑄造狀態下均屬脆性材質（延伸率均低於4.1%），但經460°C／0.5～2小時之特殊固溶處理，可使ADC12（10Si）、ADC12（11Si）及ADC12（+）三組合金之延伸率大幅提升，從4.2%、3.2%及3.9%分別提升至21.3%、21.8%及11.3%。若再經過175°C/8小時之人工時效，三組合金之UTS及延伸率分別達到：420MPa/8.5%、415MPa/6.5%及412MPa/7.9%。

關鍵字

ADC12壓鑄鋁合金 ； 機械性質 ； 特殊固溶處理 ； 時效

並列摘要

Die casting ADC12 Al alloy is widely used for many industrial applications. But due to its microstructures contain a large amount of brittle phases, including plate-like eutectic silicon and copper-rich and iron-rich precipitates, the casting products can only be used as exterior parts, not structural parts. As such, this study was conducted to improve its mechanical properties. Three ADC12-type alloys, including two commercial ADC12 alloys with different Si contents and a chemically modified ADC12 alloys, namely ADC12(10 Si), ADC12(11 Si) and ADC12(+), along with the effects of a special T6 heat treatments were examined. The results show that the cast microstructures of ADC12(10 Si) and ADC12(11 Si) alloys consist of light gray dendritic α (Al) phase as well as dark gray inter-dendritic eutectic mixture of α and Si. The ADC12(+) alloy with additions of 0.02% Sr, 0.3% Cr and 0.3% Zr exhibits modified microstructures, in which the Sr modifier and Cr neutralizer converted the shapes of coarse plate-like eutectic Si into fine fibrous-like and the thin sheet-like β-Al_5FeSi into small particles of α-Al_(13)(Fe,Cr)_4Si_4. After a special solution treatment for 0.5 to 2 hours at 460°C, the elongation of ADC12(10 Si), ADC12(11 Si) and ADC12(+) alloys increased dramatically from 4.2%, 3.2% and 3.9% to 21.3%, 21.8% and 11.3%, respectively. After subsequent artificial aging treatment of 8 hours at 175℃, the UTS and elongation of three ADC12 Al alloys are found to be 420 MPa/8.5%, 415 MPa/6.5% and 412 MPa/7.9%, respectively.

並列關鍵字

die cast ADC12 Al alloy ； elongation ； special solid solutioning treatment