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1 Vol.20 No.2 The Chinese Journal of Nonferrous Metals Feb (2010) AZ61 ( ) (MEF-4A) X (XRD-6000) (JSM-5600LV) (EPMA-1600) MTS NFW-810 AZ61 AZ MPa AZ % AZ61 AZ61 Ca TG146.2 A Effects of electromagnetic field and microalloying of Ca on microstructure and mechanical properties of wrought AZ61 magnesium alloy REN Zheng, ZHANG Xing-guo, QUE Yue, SUI Li, ZHANG Tao, JIN Jun-ze (School of Materials Science and Engineering, Foundry Research Center, Dalian University of Technology, Dalian , China) Abstract: The continuous cast of wrought magnesium alloy AZ61 with or without electromagnetic field and microalloying of Ca was investigated. The microstructures and mechanical properties of the billets were analyzed by MEF-4A metallographic microscopy, XRD-6000 diffractometry, JSM-5600LV scanning electron microscopy, EPMA-1600 electron probe microanalyser and MTS NEW-810. The results show that the billets prepared by electromagnetic cast (EMC) and microalloying of Ca have smooth surface, and the defects, such as segregation and trapped oxide, on the billet surface can be eliminated. The microstructure is improved through applying electromagnetic cast (EMC) and microalloying of Ca the refined grains and β-mg 17 Al 12 phases with small size are observed. The electromagnetic field and microalloying of Ca can improve the tensile strength, and the yield strength of AZ61 billet is 259.4MPa, increased by 24.2% compared with that of AZ61 billet by direct cold casting (DCC), but microalloying of Ca is disadvantageous to increasing the elongation of AZ61 magnesium alloy. Key words: AZ61 magnesium alloy; electromagnetic field; microalloying; Ca [1] ( ) (105052) zxgwj@dlut.edu.cn

2 20 2 AZ [2] [3 4] [5] [6 7] [8 10] [11 13] [14 17] AZ61 AZ61 1 Table 1 Chemical composition of wrought magnesium alloy (mass fraction, %) Alloy Al Zn Mn Ca Cu Fe Si Mg 5.8~ 0.7~ 0.2~ AZ Bal AZC ~ 0.7~ 0.2~ 0.07~ Bal Al-10%Mn 15 min 720 AZC6101 AZ Ca 720~ min 720 Ar/SF 6 AZ61 AZC6101 (DCC) (EMC) d t/h 1.5 mm/s 2.5 khz 10 kw ( 99.7%) ( 99.99%) ( 99.9%) ( 99.9%) Al-10%Mn 700 RJ-2 ( ( ) NaCl 36%~38% CaF 2 15%~20% MgCl 2 44%~47%) h RJ-2 1%~2% 1 Fig.1 Schematic diagram of electromagnetic cast (XRF-1800) AZ61 AZC6101 d 15 mm 20 mm 200 # 400 # 600 # 800 # # # 4% MEF-4A XRD

3 X JSM 5600LV AZC6101 (EPMA-1600) GB/T R3 MTS NEW s AZ61 AZC (a) AZ61 AZ61 10kW ( 2(b)) AZ61 ( 2.5 khz 10 kw) [5] [6] [6] α AZ61 YOU [18] CaO/MgO AZC6101 Ca Mg O 2 CaO/MgO AZ (a) (b) AZ61 AZC6101 ( 3(c) (d)) AZ61 AZ61 ( 3(e) (f) (g) (h)) 2 AZ61 (DCC) AZC6101 (EMC) Fig.2 Appearance photos of AZ61 (DCC) (a) and AZC6101 (EMC) billets (b)

4 20 2 AZ Fig.3 As-cast microstructures of wrought magnesium alloys: (a) AZ61, DCC, at billet border; (b) AZ61, DCC, at billet center; (c) AZ61, EMC, at billet border; (d) AZ61, EMC, at billet center; (e) AZC6101, DCC, at billet border; (f) AZC6101, DCC, at billet center; (g) AZC6101, EMC, at billet border; (h) AZC6101, EMC, at billet center [19] Ca Mg AZ61 Ca α-mg Ca

5 α [15] Ca GRF Fe Zr AZ MPa AZ % 5 AZ % AZ % AZ61 XRD 4 AZ61 AZC α-mg β Mg 17 Al 12 4 (a) (b) AZC6101 AZ61 AZ61 SEM 6 4 (c) (d) AZC AZ61 (Mg, Al) 2 Ca [20] ( 6(c) (d)) ( 3) AZ61 AZC6101 6(a) (b) (c) (d) AZ61 XRD 4 ( ) 4 XRD Fig.4 XRD patterns of wrought magnesium alloys: (a) AZ61, DCC; (b) AZ61, EMC; (c) AZC6101, DCC; (d) AZC6101, ECC AZC6101 Ca Ca β ( 7) Ca Mg-Al Ca Mg 17 Al [14, 16] AZ AZ61 Al 2 Ca β-mg 17 Al 12 (Al 2 Ca β-mg 17 Al 12 ) 3 5 Fig.5 Mechanical properties of wrought magnesium alloys under different conditions 1) AZ61 2)

6 20 2 AZ SEM Fig.6 SEM images of extraction phase in magnesium alloys under different conditions: (a) AZ61, DCC; (b) AZ61, EMC; (c) AZC6101, DCC; (d) AZC6101, EMC 7 AZC6101 Ca Fig.7 EPMA image of Ca and corresponding map scanning of Ca element in AZC6101 alloy (EMC) AZ61 3) AZ61 AZ61 REFERENCES [1]. [M]. :, CHEN Zhen-hua. Magnesium alloys[m]. Beijing: Chemical Industry Press, [2] YANG Z, LI J P, ZHANG J X, LORIMER G W, ROBSON J. Review on research and development of magnesium alloys[j]. Acta Metallurgica Sinica, 2008, 21(5): [3] KAINER K U. Magnesium alloys and technologies[m]. New York: Jon Wiley & Sons Ltd, [4],. [M]. :, PAN Fu-sheng, HAN En-hou. High performance magnesium alloys and processing technology[m]. Beijing: Science Press, 2007.

7 [5]. [D]. :, JIA Fei. Study of technique optimization and structure property of electromagnetic continuous casting[d]. Dalian: Dalian University of Technology, [6],,,. [J]., 1999, 35(8): REN Zhong-ming, DONG Hua-feng, DENG Kang, JIANG Guo-chang. Study of initial solidification in soft contact electromagnetic continuous casting[j]. Acta Metallurgica Sinica, 1999, 35(8): [7] LI Ting-ju, NAGAYA S, SASSA K, ASAI S. Study of meniscus behavior and surface properties during casting in a high-frequency magnetic field[j]. Metall Mater Trans B, 1995, 26: [8] HAO Hai, ZHANG Xing-guo, YAO Shan, JIN Jun-ze. Improvement of casting speed and billet quality of direct chill cast aluminum wrought alloy with combination of slit mold and electromagnetic coil[j]. Mater Trans, 2007, 48: [9] LI Jian-chao, WANG Bao-feng, MA Yong-li. Effect of complex electromagnetic stirring on inner quality of high carbon steel bloom[j]. Mater Sci Eng A, 2006, 425: [10] LI Xin-tao, GUO Zhao-xiang, ZHAO Xiang-wei. Continuous casting of copper tube billets under rotating electromagnetic field[j]. Mater Sci Eng A, 2007, 460/461: [11],,,,,. [J]., 2007, 56(9): MA Xiao-dong, ZHANG Xing-guo, REN Zheng, FANG Can-feng, HAO Hai, JIN Jun-ze. The effects of electromagnetic field on the solidification structure of magnesium alloys in EMC process[j]. Foundry, 2007, 56(9): [12],,,,. AZ61 [J]., 2006, 35(8): FANG Can-feng, ZHANG Xing-guo, JI Shou-hua, YU Yuan-hao, JIN Jun-ze. Research on soft contact electromagnetic continuous casting of AZ61 magnesium alloy[j]. Rare Metals and Materials Engineering, 2006, 35(8): [13],,,,. AZ61 [J]., 2006, 55(3): YU Yan-hao, FANG Can-feng, ZHANG Xing-guo, HAO Hai, JIN Jun-ze. Study on technology parameter and properties of AZ61 magnesium alloy under soft-contact EMC[J]. Foundry, 2006, 55(3): [14] CAO G, KOU S. Hot tearing of ternary Mg-Al-Ca alloy castings[j]. Metals Mater Trans A, 2006, 37: [15] LEE Y C, DAHLE A K, STJOHN D H. The role of solute in grain refinement of magnesium[j]. Mater Trans A, 2000, 31: [16] LI Pei-jie, TANG Bin, KANDALOVA E G. Microstructure and properties of AZ91D alloy with Ca additions[j]. Mater Lett, 2005, 59: [17] HIRAI K, SOMEKAWA H, TAKIGAW Y, HIGASHI K. Effects of Ca and Sr addition on mechanical properties of a cast AZ91 magnesium alloy at room and elevated temperature[j]. Mater Sci Eng A, 2005, 403: [18] YOU B S, PARK W W, CHUNG I S. The effect of calcium addition to magnesium on the microstructure and compositional changes of oxide film formed at high temperature[j]. Mater Trans A, 2001, 42(6): [19],,. [M]. :, ZHOU Yao-he, HU Zhuang-qi, JIE Wan-qi. Solidification technology[m]. Beijing: China Machine Press, [20] YUSUKE N, AKIRA W, OHORI K. Effects of Ca, Sr addition on properties of Mg-Al based alloys[j]. Mater Trans A, 2006, 47(4): ( )

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