Abstract
The rheo-squeeze casting (RSC) process is a newly-developed casting process for high-performance components. In order to further improve the mechanical properties of magnesium alloys, AZ91-2wt.%Ca (AZX912) alloy was prepared by the RSC process and then subjected to heat treatment. The microstructure evolution and mechanical properties of AZX912 alloy during heat treatment were investigated. It was found that during solid solution treatment at 410 °C, β-Mg17Al12 phase with low melting point dissolves into α-Mg matrix, while the connected network-like Al2Ca phase with high melting point tends to separate gradually, and the tips of Al2Ca phase is partially spheroidized. With the increase of solid solution time, the yield strength (YS) of AZX912 alloy decreases gradually while the ultimate tensile strength (UTS) and elongation to failure (Ef) increase continuously. Isothermal ageing at 225 °C promotes the precipitation of β-Mg17Al12 phase in the matrix of AZX912 alloy. The hardness reaches the peak after ageing for 96 h and the increase in hardness is about 24.8%. The precipitation of β-Mg17Al12 phase during ageing treatment is beneficial to YS but harmful to Ef. The mechanism of microstructure evolution during heat treatment and its effect on mechanical properties are discussed.
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Kabirian F, Mahmudi R. Effects of Rare Earth Element Additions on the Impression Creep Behavior of AZ91 Magnesium Alloy. Metall Mater Trans A, 2009, 40: 2190–2201.
Cheng Suling, Yang Gencang, Fan Jianfeng, et al. Effect of Ca and Y additions on oxidation behavior of AZ91 alloy at elevated temperatures. Trans Nonferrous Met Soc China, 2009, 19: 299–304.
Amberger D, Eisenlohr P, Goken M. Microstructural evolution during creep of Ca-containing AZ91. Mater Sci Eng A, 2009, 510: 98–402.
Amberger D, Eisenlohr P, Goken M. On the importance of a connected hard-phase skeleton for the creep resistance of Mg alloys. Acta Mater, 2012, 60: 2277–2289.
Wu Guohua, Fan Yu, Gao Hongtao, et al. The effect of Ca and rare earth elements on the microstructure, mechanical properties and corrosion behavior of AZ91D. Mater Sci Eng A, 2005, 408: 255–63.
Fan Z. Semisolid metal processing. Int Mater Rev, 2002, 47: 49–85.
Wu Shusen, Lu Shulin, An Ping, et al. Microstructure and property of rheocastlng aluminum-alloy made with Indirect ultrasonic vibration process. Mater Lett, 2012, 73:150–153.
Dai Wei, Wu Shusen, Lu Shulin, et al. Effects of rheo-squeeze casting parameters on microstructure and mechanical properties of AlCuMnTi alloy. Mater Sci Eng A, 2012, 538: 320–326.
Lu Shulin, Wu Shusen, Dal Wei, et al. The indirect ultrasonic vibration process for rheo-squeeze casting of A356 aluminum alloy. J Mater Process Technol, 2012, 212:1281–1287.
Mahathaninwong N, Plookphol T, Wannasin J, et al. T6 heat treatment of rheocasting 7075 Al alloy. Mater Sci Eng A, 2012, 532: 91–99.
Esgandari B A, Mehrjoo H, Nami B, et al. The effect of Ca and RE elements on the precipitation kinetics of Mg17Al12 phase during artificial aging of magnesium alloy AZ91. Mater Sci Eng A, 2011, 528: 5018–5024.
Wang Qudong, Chen Wenzhou, Zeng Xiaoqin, et al. Effects of Ca addition on the microstructure and mechanical properties of AZ91 magnesium alloy. J Mater Sci, 2001, 36: 3035–3040.
Zhang Yang, Wu Guohua, Liu Wencai, et al. Microstructure and mechanical properties of rheo-squeeze casting AZ91-Ca magnesium alloy prepared by gas bubbling process. Mater Des, 2015: 67: 1–8.
Xue Feng, Ming Xuegang, Sun Yangshan. Microstructures and mechanical properties of AZ91 alloy with combined additions of Ca and Si. J Mater Sci, 2006, 41: 4725–4731.
Zhang Yang, Wu Guohua, Liu Wencai, et al. Preparation and rheo-squeeze casting of seml-solld AZ91-2wt.%Ca magnesium alloy by gas bubbling process. J Mater Res, 2015, 30: 825–832.
Liang S M, Chen R S, Blandin J J, et al. Thermal analysis and solidification pathways of Mg-Al-Ca system alloys. Mater Sci Eng A, 2008, 480: 365–372.
Zhang Jumei, Wang Zhlhu, Jiang Bailing, et al. Influence of annealing and spheroidizing treatment on microstructure and mechanical properties of AZ91 magnesium alloy. China Foundry, 2013, 10: 34–38.
Wang Zhiwei, Yan Hong, Huang Wenxian. Effect of solution treatment on microstructure and hardness of rheo-forming AZ91-Y alloy. China Foundry, 2016, 13: 383–388.
Caceres C H, Davidson C J, Griffiths J R, et al. Effects of solidification rate and ageing on the microstructure and mechanical properties of AZ91 alloy. Mater Sci Eng A, 2002, 325: 344–355.
Srinivasan A, Pillai U T S, Pal B C. Effects of elemental additions (SI and Sb) on the ageing behavior of AZ91 magnesium alloy. Mater Sci Eng A, 2010, 527: 6543–6550.
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*Yang Zhang Male, born in 1988, Lecturer, Ph. D. His research interests mainly focus on the semi-solid processing of Mg alloys and super-light Mg-Li alloys. To date, he has published more than 10 papers.
This work was financially supported by National Natural Science Foundation of China (No. 51601076 and No. 51401093) and Natural Science Fund for Colleges and Universities in Jiangsu Province (No. 16KJB430013).
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Zhang, Y., Li, Xp., Sun, Sp. et al. Microstructure evolution and mechanical properties of rheo-squeeze casting AZ91-Ca alloy during heat treatment. China Foundry 14, 485–491 (2017). https://doi.org/10.1007/s41230-017-7025-y
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DOI: https://doi.org/10.1007/s41230-017-7025-y