强化冷却搅拌制备A356铝合金半固态组织
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摘要
针对现有搅拌轴与熔体换热不稳定,通过向搅拌轴内通入冷却水,自主设计了强化冷却搅拌装置,研究了装置的搅拌时间、搅拌速度和冷却条件对A356铝合金半固态微观组织的影响规律和熔体的凝固过程。实验结果表明:搅拌轴对熔体进行冷却和搅拌来提高熔体对流与换热,适当地提高搅拌转速,延长搅拌时间,微观组织逐渐由枝状晶转为球状晶,形貌变得越来越圆整;水冷却叠加搅拌促进了搅拌轴的散热,有利于熔体更快地降温,获得更大的过冷度,从而提高晶粒数量,改善晶粒形貌。
Aiming at the unstable heat transfer between the mixing shaft and the melt, an enhanced cooling mixing device was self-designed by introducing cooling water into the mixing shaft. The effects of rotation time, rotation speed and cooling condition on the microstructure of semisolid A356 aluminum alloy and the solidification process of melt were investigated.The results show that the melt is cooled and stirred by the mixing shaft to improve the convection and heat transfer. When the stirring speed and stirring time increase properly, the grains gradually change from dendrite to spheroid crystal, and the morphology becomes more and more round. Water cooling superimposed mixing technology promotes the heat dissipation of the mixing shaft. It is beneficial to faster cooling of melt and getting a bigger overcooling degree, thus increasing the grain number and improving the grain morphology.
Aiming at the unstable heat transfer between the mixing shaft and the melt, an enhanced cooling mixing device was self-designed by introducing cooling water into the mixing shaft. The effects of rotation time, rotation speed and cooling condition on the microstructure of semisolid A356 aluminum alloy and the solidification process of melt were investigated.The results show that the melt is cooled and stirred by the mixing shaft to improve the convection and heat transfer. When the stirring speed and stirring time increase properly, the grains gradually change from dendrite to spheroid crystal, and the morphology becomes more and more round. Water cooling superimposed mixing technology promotes the heat dissipation of the mixing shaft. It is beneficial to faster cooling of melt and getting a bigger overcooling degree, thus increasing the grain number and improving the grain morphology.
引文
[1] Liu Z Y, Mao W M, Wang W P, et al. Preparation of semi-solid A380 aluminum alloy slurry by serpentine channel[J]. Transactions of Nonferrous Metals Society of China, 2015, 25(5):1419-1426.
[2] Fang X G, Lu S L, Zhao L, et al.Microstructure and mechanical properties of a novel Mg-Re-Zn-Y alloy fabricated by rheo-squeeze casting[J]. Materials and Design, 2016, 94:353-359.
[3] Shabextari S G, Honarmand M, Saghafian H. Microstructural evolution of A380 aluminum alloy produced by gas-induced semi-solid technique(GISS)[J]. Advances in Materials and Processing Technologies, 2015, 1(1/2):155-163.
[4]周冰,康永林,祁明凡,等. AZ91D镁合金强制对流流变压铸组织与性能[J].材料工程,2014(10):1-5.
[5] Flemings M C, Martins R, Figueredo de A M, et al. Efficient formation of structures suitable for semi-solid forming[C]//The21th International Die Casting Congress.Cincinnati,2001:79-84.
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[7] Seo P K, Lee S M, Kang C G. A new process proposal for continuous fabrication of rheological material by rotational barrel with stirring screw and its microstructural evoluation[J]. Journal of Material Processing Technology, 2009, 209(1):171-180.
[8] Zhang F, Kang Y L, Yang L Q, et al. Taper barrel rheomoulding process for semisolid slurry preparation and microstructure evolution of A356 aluminum alloy[J]. Transactions of Nonferrous Metals Society of China, 2010,20(9):1677-1684.
[9] Zhou B, Kang Y L, Qi M F, et al. R-HPDC process with forced convection mixing device for automotive part of A380 aluminum alloy[J]. Materials, 2014, 7(4):3084-3105.
[10] Qi M F, Kang Y L, Zhou B, et al. A forced convection stirring process for Rheo-HPDC aluminum and magnesium alloy[J].Journal of Materials Processing Technology,2016,234:353-367.
[11] Flemings M C. Behavior of metal alloys in the semi-solid state[J]. Metallurgical Transactions B, 1991, 22(3):269-293.
[12] Doherty R D, Lee Ho-In, Feest E A. Microstructure of stir-cast metals[J]. Materials Science and Engineering, 1984, 65(1):181-189.
[13]管仁国,马伟民.金属半固态成形理论与技术[M].北京:冶金工业出版社,2005.
[14]李涛,陈光,林鑫,等.搅拌条件下二元合金凝固组织的形态演化[J].金属学报,2006,42(6):577-583.
[15] Das A, Fan Z. Morphology development of solidification structure under forced fluid flow:experimental observation[J]. Materials Science and Technology, 2013, 19(5):573-580.
[16] Pilling J, Hellawell A. Mechanical deformation of dendrites by fluid flow[J]. Metallurgical and Materials Transactions A,1996, 27(1):229-232.
[17] Zhou B, Kang Y L, Zhu G M, et al. Forced convection rheoforming process for semisolid slurry preparation and numerical simulation of 7075 aluminum alloy[J].Transactions of Nonferrous Metals Society of China, 2014, 24(4):1109-1116.
[18]张景新,张奎,刘国钧,等.电磁搅拌制备半固态材料非枝晶组织的形成机制[J].中国有色金属学报. 2000, 10(4):511-515.
[2] Fang X G, Lu S L, Zhao L, et al.Microstructure and mechanical properties of a novel Mg-Re-Zn-Y alloy fabricated by rheo-squeeze casting[J]. Materials and Design, 2016, 94:353-359.
[3] Shabextari S G, Honarmand M, Saghafian H. Microstructural evolution of A380 aluminum alloy produced by gas-induced semi-solid technique(GISS)[J]. Advances in Materials and Processing Technologies, 2015, 1(1/2):155-163.
[4]周冰,康永林,祁明凡,等. AZ91D镁合金强制对流流变压铸组织与性能[J].材料工程,2014(10):1-5.
[5] Flemings M C, Martins R, Figueredo de A M, et al. Efficient formation of structures suitable for semi-solid forming[C]//The21th International Die Casting Congress.Cincinnati,2001:79-84.
[6] Ji S, Fan Z, Bevis M J. Semi-solid processing of engineering alloys by a twin-screw rheomoulding process[J]. Material Science and Engineering A,2001, 299:210-217.
[7] Seo P K, Lee S M, Kang C G. A new process proposal for continuous fabrication of rheological material by rotational barrel with stirring screw and its microstructural evoluation[J]. Journal of Material Processing Technology, 2009, 209(1):171-180.
[8] Zhang F, Kang Y L, Yang L Q, et al. Taper barrel rheomoulding process for semisolid slurry preparation and microstructure evolution of A356 aluminum alloy[J]. Transactions of Nonferrous Metals Society of China, 2010,20(9):1677-1684.
[9] Zhou B, Kang Y L, Qi M F, et al. R-HPDC process with forced convection mixing device for automotive part of A380 aluminum alloy[J]. Materials, 2014, 7(4):3084-3105.
[10] Qi M F, Kang Y L, Zhou B, et al. A forced convection stirring process for Rheo-HPDC aluminum and magnesium alloy[J].Journal of Materials Processing Technology,2016,234:353-367.
[11] Flemings M C. Behavior of metal alloys in the semi-solid state[J]. Metallurgical Transactions B, 1991, 22(3):269-293.
[12] Doherty R D, Lee Ho-In, Feest E A. Microstructure of stir-cast metals[J]. Materials Science and Engineering, 1984, 65(1):181-189.
[13]管仁国,马伟民.金属半固态成形理论与技术[M].北京:冶金工业出版社,2005.
[14]李涛,陈光,林鑫,等.搅拌条件下二元合金凝固组织的形态演化[J].金属学报,2006,42(6):577-583.
[15] Das A, Fan Z. Morphology development of solidification structure under forced fluid flow:experimental observation[J]. Materials Science and Technology, 2013, 19(5):573-580.
[16] Pilling J, Hellawell A. Mechanical deformation of dendrites by fluid flow[J]. Metallurgical and Materials Transactions A,1996, 27(1):229-232.
[17] Zhou B, Kang Y L, Zhu G M, et al. Forced convection rheoforming process for semisolid slurry preparation and numerical simulation of 7075 aluminum alloy[J].Transactions of Nonferrous Metals Society of China, 2014, 24(4):1109-1116.
[18]张景新,张奎,刘国钧,等.电磁搅拌制备半固态材料非枝晶组织的形成机制[J].中国有色金属学报. 2000, 10(4):511-515.