| 摘要(英) |
This study investigates low-pressure casting experiments of A356 (Al-Si-Mg) aluminum alloy castings with varying thicknesses. The objective is to explore the flow filling and oxide film formation conditions and mechanisms in practical casting applications. By adjusting casting parameters such as low-pressure casting pressure, pressurization time, and mold preheating temperature, the study examines the issues of filling flow fronts. The findings are validated and analyzed using MAGMA 5.5 simulation software.
The experiments reveal that thicker castings exhibit better mechanical properties due to adequate holding pressure and complete filling, which provide sufficient dendritic arm spacing compensation. In contrast, 2.8 mm thick plates experience unstable flow at the tail end of the aluminum melt due to excessive pressure during mold filling, causing wave entrainment and air entrapment. This results in air and oxide film accumulation in the midsection of the test specimen, leading to poorer mechanical properties. Key findings are summarized as follows:
For 2.8 mm thick aluminum alloy plates in low-pressure casting, the proportion of wave entrainment and splashing is higher on the left side than on the right. Air entrapment forms at the mold entrance and propagates through the entire specimen, reducing mechanical properties on the left side compared to the right.
For 3.2 mm thick plates, wave entrainment, air entrapment, and splashing are all more pronounced on the left side than on the right. Air entrapment occurs due to excessive inlet flow speed, leading to flow front instability. Mechanical properties on the left side are inferior to those on the right.
For 4.5 mm thick plates, the proportion of air entrapment and splashing is higher on the right side than on the left. Although wave entrainment is slightly greater on the left, the difference is not significant. Mechanical properties on the left side surpass those on the right.
For 6.5 mm thick plates, the proportion of air entrapment, wave entrainment, and splashing is higher on the right side than on the left. Due to greater thickness, the internal filling process is slower and more stable, while the outer side provides more space for wave entrainment. Mechanical properties on the left side exceed those on the right.
During the filling process, plates located on the outer side exhibit higher inlet flow speeds than those on the inner side. The inlet speed affects the splashing ratio during mold filling. Splashing is highly unstable and often results in incomplete filling, causing air entrapment in the molten aluminum or rapid backflow to the tail end of the specimen, leading to significant air entrapment and increased oxide film and inclusion proportions.
Keywords: A356 aluminum alloy, low-pressure casting, oxide film, numerical simulation, mechanical properties
The experiments reveal that thicker cast specimens exhibit better mechanical properties due to sufficient holding pressure and time, which ensure complete filling and refinement of dendritic arm spacing. Conversely, for 2.8 mm thick plates, excessive pressure during mold filling causes unstable flow at the rear end of the aluminum liquid, resulting in wall impact, turbulence, and entrainment of air into the molten aluminum. This leads to the formation of excessive oxide films in the central section of the specimens, adversely affecting their mechanical properties.
For 2.8 mm thick plates in low-pressure casting:
The proportions of turbulence and splashing are greater on the left side than on the right.
Air entrainment forms at the mold entry point and propagates throughout the specimen with the molten aluminum′s flow, causing the left side to exhibit inferior mechanical properties compared to the right.
For 3.2 mm thick plates in low-pressure casting:
The proportions of air entrainment, turbulence, and splashing are also greater on the left side than on the right.
Air entrainment results from excessive flow speed at the mold entry, leading to instability in the flow front, causing the left side′s mechanical properties to be inferior to the right.
For 4.5 mm thick plates in low-pressure casting:
Air entrainment and splashing proportions are greater on the right side than on the left.
Although turbulence is slightly higher on the left side, the difference is not significant, and the left side exhibits superior mechanical properties compared to the right.
For 6.5 mm thick plates in low-pressure casting:
The proportions of air entrainment, turbulence, and splashing are all higher on the right side than on the left.
Due to the greater thickness, the flow speed during inner filling is slower and more stable, while the outer region experiences more turbulence due to the increased space, resulting in the left side having better mechanical properties than the right.
During the filling process, the outer plates have a higher mold entry speed than the inner plates. This entry speed influences the proportion of splashing during mold filling. Splashing is a highly unstable surface flow phenomenon, where the flow front may advance without complete filling, leading to air entrainment in the molten aluminum or backflow at the specimen′s rear end. This generates a large amount of air entrainment, significantly increasing the proportion of inclusions and oxide films. |
| 參考文獻 |
[1]https://kknews.cc/news/v65p48l.html. In.
[2]https://www.corrdata.org.cn/news/industry/2017-04-12/165323.html.
[3]Wang, P.-W. (2001). 除氣與除渣處理對於鋁合金品質的影響 National Central University].
[4]Crepeau, P. N. (1997). Molten aluminium contamination: Gas, inclusions and dross. Modern casting, 87(7), 39-41.
[5]Ye, J., & Sahai, Y. (1996). Interfacial behavior and coalescence of aluminum drops in molten salts. Materials Transactions, JIM, 37(2), 175-180.
[6]Roy, R. R., & Sahai, Y. (1997). Coalescence behavior of aluminum alloy drops in molten salts. Materials Transactions, JIM, 38(11), 995-1003.
[7]Cochran, B., Fenyes, M., Jeanneret, J., Mulae, R., & Crepeau, P. (1992). Flux practice in aluminum melting. AFS Transactions, 88, 737-742.
[8]http://alupure.com/gas_show-122.html.
[9]Huang, L.-W., Wang, P.-W., Shih, T.-S., & Liou, J.-H. (2002). Effect of degassing treatment on the quality of Al-7Si and A356 melts. Materials Transactions, 43(11), 2913-2920.
[10]Van Der Graaf, G., Van Den Akker, H., & Katgerman, L. (2001). A computational and experimental study on mold filling. Metallurgical and Materials Transactions B, 32, 69-78.
[11]Baum, M., Jasser, F., Stricker, M., Anders, D., & Lake, S. (2022). Numerical simulation of the mold filling process and its experimental validation. The International Journal of Advanced Manufacturing Technology, 120(5), 3065-3076.
[12]Park, J. M. (2010). Behaviours of bifilms in A356 alloy during solidification: developing observation techniques with 3-D micro x-ray tomography University of Birmingham].
[13]Liu, J., Wang, Q., & Qi, Y. (2019). Atomistic simulation of the formation and fracture of oxide bifilms in cast aluminum. Acta Materialia, 164, 673-682.
[14]Wang, Q., Crepeau, P., Davidson, C., & Griffiths, J. (2006). Oxide films, pores and the fatigue lives of cast aluminum alloys. Metallurgical and Materials Transactions B, 37, 887-895.
[15]Campbell, J. (2003). Castings. Elsevier.
[16]Tezer, F., Gursoy, O., Erzi, E., Zora?a, M., & D??p?nar, D. (2019). Determination of Liquid Metal Quality with Deep Etching Method. Shape Casting: 7th International Symposium Celebrating Prof. John Campbell′s 80th Birthday,
[17]Campbell, J. (2006). Entrainment defects. Materials science and technology, 22(2), 127-145.
[18]黃儒祥, & 許富淵. (2020). 回收鋁中氧化物雜質在保溫爐內沉澱現象之模擬及驗證. 鑄造工程學刊, 46(1), 25-40.
[19]Divandari, M., & Campbell, J. (2001). Mechanisms of bubble trail formation in castings. Trans. AFS, 109, 433-442.
[20]Shih, T.-S., Chen, P.-C., & Huang, Y.-S. (2011). Effects of the hydrogen content on the development of anodic aluminum oxide film on pure aluminum. Thin Solid Films, 519(22), 7817-7825.
[21]Chen, Y.-J., Huang, L.-W., & Shih, T.-S. (2003). Marking oxide films on the section of Al-XSi alloys by ultrasonic-vibration treatment. Materials Transactions, 44(6), 1190-1197.
[22]Huang, L.-W. (2003). 製程參數對鑄造鋁合金品質影響之研究 National Central University].
[23]李?栻. (2008). 金?液面氧化膜??合金?件?量的影?. 金?加工: ?加工(9), 56-58.
[24]Smith, T. (1966). Kinetics and mechanism of hydrogen permeation of oxide films on zirconium. Journal of Nuclear Materials, 18(3), 323-336.
[25]黃文星. (2000). 低壓鑄造製程灌模及凝固數值模擬系統之研發與實驗驗證 (3/3).
[26]Merlin, M., Timelli, G., Bonollo, F., & Garagnani, G. L. (2009). Impact behaviour of A356 alloy for low-pressure die casting automotive wheels. Journal of Materials Processing Technology, 209(2), 1060-1073.
[27]Bahmani, A., Hatami, N., Varahram, N., Davami, P., & Shabani, M. O. (2013). A mathematical model for prediction of microporosity in aluminum alloy A356. The International Journal of Advanced Manufacturing Technology, 64, 1313-1321.
[28]Yang, X., Din, T., & Campbell, J. (1998). Liquid metal flow in moulds with off-set sprue. International Journal of Cast Metals Research, 11(1), 1-12.
[29]D’Elia, F., Ravindran, C., Sediako, D., Kainer, K., & Hort, N. (2014). Hot tearing mechanisms of B206 aluminum–copper alloy. Materials & Design, 64, 44-55.
[30]孔令超. (2015). ?合金低??造?程的模?. ?造技?, 36(6), 1513-1517.
[31]Argo, D., & Gruzleski, J. (1988). Porosity in modified aluminum alloy castings. AFS Transactions, 96(1), 65-74.
[32]Sigworth, G. (1987). A scientific basis for degassing aluminum. AFS Transactions, 95, 73-78.
[33]https://www.zwickroell.com/tw/industries/metals/metals-standards/metals-tensile-test-astm-e8/ |
[Endnote RIS 格式]
[相關文章]
[文章引用]
[完整記錄]
[館藏目錄]
至系統瀏覽論文 (2030-1-31以後開放)
plurk
funp
live
udn
HD
myshare
netvibes
friend
youpush
delicious
baidu
Google bookmarks
del.icio.us
hemidemi
facebook
twitter
google
reddit