Investigation of The Effect of Semi-Solid Temperatures and Holding Times at Isothermal Range On Microstructure of AZ31 Mg Alloy

Yıl 2023, Cilt: 11 Sayı: 1, 10 - 24, 25.03.2023

Bahadır Akgün , Kadir Kocatepe

https://doi.org/10.29109/gujsc.1187050

Öz

Mg alloys have poor formability due to their hexagonal tightly packed (HCP) crystal structure, low active shear system at room temperature, and anisotropic behavior in polycrystalline structure. While this situation hindered the development and commercialization of Mg alloys to some extent in the past, today developments in machining, liquid forming and semi-solid forming technology have removed these obstacles. Semi-solid forming of alloys has been the subject of intense R&D since it was discovered in the 1970s. In the semi-solid forming method, it is aimed to obtain ideal microstructure of the alloy, including excellent fluidity, appropriate flow control, adjustable viscosity and controllable grain morphology, thanks to equiaxed spherical solid particles surrounded by liquid. In this study, it is aimed to achieve the spherical microstructure required for the semi-solid shaping of the extruded AZ31 Mg alloy by heating to semi-solid temperatures and isothermal holding in the semi-solid temperature range. To accomplish this objective, rapid heating in the induction coil and controlled holding in the isothermal temperature range were applied to the alloy. Heating the extruded AZ31 Mg alloy to a semi-solid temperature (565-630°C) and subsequently rapid cooling processes lead to many intermetallic Mg17Al12(γ) compounds with heterogeneous distribution both in the equiaxed primary Mg(α) grains and at the grain boundaries as well as a very little eutectic at the grain boundaries. As the semi-solid temperature value increased, the degree of spheroidization increased. However, it was found that the grain growth reached a maximum at one point and there was no significant change in the shape factor as a result of controlled holding time.

Anahtar Kelimeler

Semi-Solid Process, Spheroidization, Shape Factor, Grain Growth, Soaking time

Proje Numarası

6273

Kaynakça

• Chang, Z., et al., Semisolid rheoforming of magnesium alloys: A review. Materials & Design, 2020. 195.
• Feng, J., et al., Improved microstructures of AZ31 magnesium alloy by semi-solid extrusion. Materials Science and Engineering: A, 2021. 800.
• Kiuchi, M. and R. Kopp, Mushy/semi-solid metal forming technology–Present and Future. Cirp annals, 2002. 51(2): p. 653-670.
• Pola, A., M. Tocci, and P. Kapranos, Microstructure and properties of semi-solid aluminum alloys: a literature review. Metals, 2018. 8(3): p. 181.
• Meng, Y., et al., Cold formability of AZ31 wrought magnesium alloy undergoing semisolid spheroidization treatment. Materials Science and Engineering: A, 2015. 624: p. 148-156.
• Xu, Y., et al., Microstructure evolution of a SIMA processed AZ91D magnesium alloy based on repetitive upsetting-extrusion (RUE) process. Materials Characterization, 2016. 118: p. 309-323.
• Xu, Y., et al., Thixoforming of semi-solid AZ91D alloy with high solid fraction prepared by the RUE-based SIMA process. The International Journal of Advanced Manufacturing Technology, 2017. 93(9-12): p. 4317-4328.
• Tzimas, E. and A. Zavaliangos, Evaluation of volume fraction of solid in alloys formed by semisolid processing. Journal of Materials Science, 2000. 35(21): p. 5319-5330.
• Mirković, D. and R. Schmid-Fetzer, Solidification Curves for Commercial Mg Alloys Determined from Differential Scanning Calorimetry with Improved Heat-Transfer Modeling. Metallurgical and Materials Transactions A, 2007. 38(10): p. 2575-2592.
• Ohno, M., D. Mirkovic, and R. Schmid-Fetzer, Phase equilibria and solidification of Mg-rich Mg–Al–Zn alloys. Materials Science and Engineering: A, 2006. 421(1-2): p. 328-337.
• Kılıçlı, V., Yarı-katı döküm tekniği üretilen Al-Zn alaşımlarında yapı-özellik ilişkisinin incelenmesi. Mayıs 2010.
• Özer, M., Yarı-Katı Döküm Teknİğİ İle Üretİlen Al-Si Alaşımlarinda Yapı-Özellİk İlİşkİsİnİn İncelenmesi. 2010.
• Mohammadi, J., M. Ghoreishi, and Y. Behnamian, An investigation into the dissolution characteristics of γ precipitates in Mg-3Al-Zn alloy. Materials Research, 2014. 17(4): p. 996-1002.
• Totalmateria, AZ31B (GB). 2021.
• Monas, A., et al., Divorced Eutectic Solidification of Mg-Al Alloys. Jom, 2015. 67(8): p. 1805-1811.
• Zhao, Z., et al., Microstructural evolution of an ECAE-formed ZK60-RE magnesium alloy in the semi-solid state. Materials Science and Engineering: A, 2009. 506(1-2): p. 8-15.
• Fan, L., et al., The semi-solid microstructural evolution and coarsening kinetics of AZ80-0.2Y-0.15Ca magnesium alloy. Materials Characterization, 2019. 154: p. 116-126.
• Wang, L.-p., et al., Spheroidal microstructure formation and thixoforming of AM60B magnesium alloy prepared by SIMA process. Transactions of Nonferrous Metals Society of China, 2012. 22: p. s435-s444.
• Xu, H.Y., Z.S. Ji, and Z.Y. Wang, Microstructural Evolution of AZ91D-1.5%Er during Semi-Solid Isothermal Treatment. Solid State Phenomena, 2012. 192-193: p. 238-245.
• Xu, G., et al., Thermodynamic database of multi-component Mg alloys and its application to solidification and heat treatment. Journal of Magnesium and Alloys, 2016. 4(4): p. 249-264.