在不同Al-Al4C3细化剂添加量条件下, 对纯Mg熔体进行孕育处理. 当添加质量分数为1.0%Al-Al4C3细化剂时细化效果最佳, α-Mg晶粒平均尺寸由毫米级降至106 μm. 在纯Mg熔体中施加不同功率超声场, 当施振功率为600 W时细化效果最好. 研究表明, 空化泡破碎产生的过冷对形核具有促进作用, 空化泡的破裂及声流对熔体的搅动使得细小枝晶破碎, 形成新的结晶核心, 这一过程对形核起主要作用. 功率超声与Al-Al4C3细化剂共同作用于纯Mg熔体过程, 可以显著细化晶粒. 其机理为超声对杂质的“活化”作用.
The melt of pure Mg was inoculated at the conditions of different addition amounts of Al–Al4C3 refiner. When adding 1.0%Al–Al4C3 refiner, the refining effect is the best and the average grain size of α–Mg is reduced from millimeter level to 106 μm. Ultrasound fields with different power levels were applied on the melt of pure magnesium and the best refining effect was obtained when the power was 600 W. The results show that the undercooling formed by breakdown of cavitation bubbles may have a promoting effect to nucleate. The breakdown of cavitation bubbles and the agitations of acoustic stream on the melt cause the fragmentation of fine dendritic crystal which could form new crystallization nuclei, this process plays the main role for nucleating in the melt. The combined application of ultrasound and Al–Al4C3 refiner to the melt of pure Mg could significantly refine its grain. The mechanism would be an the activation effect of ultrasound on the impurities in the melt.
[1] Kojima Y. Plaftorm science and technology for advanced magnesium alloys[J]. Materials Science Forum, 2000 ,350351:3 -18.
[2] Watanabe H , Tsutsui H, Mukai T, et al. Super plastic behavoir in commercial wrought magnesium alloys[J] . Mater2ials Science Forum , 2000 , 350 351 : 171 -176.
[3] Mukai T, Watanabe H, Higashi K. Grain refinement of commercial magnesium alloys for high-strain-rate-super plastic forming[J].Materials Science Forum, 2000,350-351:159-170
[4] Tamura Y, Kono N, Motegi T, Sato E. Grain refining mechanism and casting structure of Mg-Zr alloys[J].Journal of Japan Institute of Light Metals, 1998,48(4):185-189
[5] Bramffit Bruce L. The effect of carbide and nitride additions on the heterogeneous nucleation behavior of liquid iron[J]. Metallurgical Transaction A, 1970, 1(7): 1987?1995.
[6] Eskin G I. Ultrasonic Treatment of Light Alloy Melts[M]. Amsterdam: Gordon and Breach,1998.
[7] Eskin G I.Broad prospects for commercial application of the ultrasonic(cavitation) melt treatment of light alloys[J].Ultrasonics Sonochemistry,2001,8(3):319-325.
[8] 陈锋．振动作用下铝合金的凝固、组织及性能特点[D]．南京：东南大学，1991．
[9] Komarov S V.Kuwabara M, Abramov O V. High power ultrasonics in pyrometallurgy: Current status and recent
development[J]. Isij Internatjonal, 2005, 45(12): l765—1782.
[10] 肖慎修，王崇愚，陈天朗。1998密度泛函理论的离散变分方法在化学和材料物理学中的应用(北京：科学出版社) 第92页
(Xiao Shen-xiu,Wang Chong-yu,Chen Tian-lang 1998 The Application of the Discrete Variational Method in the Density Functional Theory to Chemistry and Materials Physics (Beijing : Science Press) p92 (in Chinese)
[11] Yasudak, Saiki Y, Kubot, et a1. Influence of high-power ultrasonic irradiation on primary nucleation process during solidification[J]. Japanese Journal of Applied Physics, 2007, 46(7B): 4939—4944.
