Study on Processing Conditions for Semi-Solid Forging of Magnesium Alloys

Abstract:

Magnesium alloy castings are mainly formed by the die casting method, but this method has the disadvantage that product properties such as strength vary due to many defects inherent in casting. In this study, AZX912 (a flame-retardant magnesium alloy with 2% calcium added to AZ91D alloy) was semi-solid forged using a servo press and die cushion system to stabilize product properties. Experiments were conducted to refine the α-phase and reduce the yield point, and the stirring speed was changed and its effect was investigated. Observation of the microstructure of the molded product using an optical microscope showed that the average grain size of the α-phase became smaller as the stirring speed increased. Tensile tests were conducted on specimens cut from the compacts, and the yield point increased as the stirring speed increased. This is thought to be due to compliance with Hall Petch's law. The microstructure of the molded product was observed under an optical microscope and showed a three-layer structure with a dendrite shape in the upper part (about 5%), a grain structure in the middle part (over 90%), and a chill layer in the lower part (less than 5%). Comparison of the thickness of the chill layer showed that the thickness of the chill layer decreased as the solidus ratio increased.

• Periodical: Solid State Phenomena (Volume 348)
• Pages: 21-26
• DOI: https://doi.org/10.4028/p-2HlJZU
• Online since: August 2023
• Authors: Shuji Furuta, Hiroki Nakagawa, Tatsuya Tanaka*, Masahiro Sasada, Shinichi Nishida, Shun Yasuhara, Hayato Ueno
• Keywords: AZX912, Diecushion, Magnesium Alloys, Semi Solid Forging, Servo Press, Tensile Test

References

[1] Saikawa, S, "Development trend of magnesium alloy castings for automotive lightening", J. JILM, Vol. 60, No11 (1995), pp.571-577 (in Japanese).

[2] Sakakibara, k." Die casting of magnesium", J. JILM, Vol. 59 (2009), pp.464-475(in Japanese).

[3] Kamado, S. and Kojima, Y. "Semi-solid Stir-casting and Forming of Magnesium Alloys", Materia Japan Vol. 33, No.9(1994), pp.1149-1158(in Japanese).

DOI: 10.2320/materia.33.1149

[4] Namba, A. "Semi-solid metal processing", J. JILM, Vol. 45 (1995), pp.346-354(in Japanese).

[5] Jun Yanagimoto, Jian-Bo Tan , Sumio Sugiyama and Yi Meng: "Controlled Semisolid Forging of Aluminium Alloys Using Mechanical Servo Press to Manufacture Products with Homo- and Heterogeneous Microstructures", Materials Transactions, Vol. 54, No. 7 (2013) pp.1149-1154

DOI: 10.2320/matertrans.m2013098

[6] Sugiyama, S." General review on semisolid processing", Production Research, Vol. 65, No.6 (2013), pp.803-809(in Japanese).

[7] Shuji FURUTA, Tatsuya TANAKA, Masahiro SASADA, Shinichi NISHIDAand Inomi ISOBE "Study on semi-solid forging of magnesium alloys", ICM&P2022,Tu-1C-1