Effects of Grain Refining and Modification on Mechanical Properties and Microstructures of Multielement Al-7.5Si Cast Alloy

Abstract:

With orthogonal tests the effects of grain refiners and modifiers, Al-10Sr, rare earth (RE) and Al-Ti-5B, on the mechanical properties of Al-Si alloy for automobile cylinder blocks were studied. The best result occurred when the proportion of refiners and modifiers was Al-10Sr = 0.1wt%, RE = 0.3wt%, Al-5Ti-B = 0.8wt%. With SEM and EDS the as-cast microstructures of materials after grain refining and modification were observed and analyzed. Tiny branch-shaped AlSi phase, thin-striped AlCu phase, new small bone-shaped AlSiMn phase, new leaf-shaped or feathered B(AlCuCe) phase as well as the phases of other metal compounds made the as-cast microstructures more complicated and more compact after grain refining and modification. Some brittle phases reduced in size obviously and distributed in the grain boundaries of plastic α-phase in network, which acted as intercrystalline strengthening to certain degree. During the tensile deformation these brittle phases could reduce the stress concentration, impeded dislocation movement, and then strengthened the alloy matrix. In addition after grain refining and modification the porosity was significantly reduced.

• Periodical: Applied Mechanics and Materials (Volume 312)
• Pages: 396-401
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.312.396
• Online since: February 2013
• Authors: Guang Lei Liu, Nai Chao Si
• Keywords: Al-Si Alloy, Grain Modification, Grain Refining, Mechanical Property, Microstructure, Orthogonal Testing

References

[1] Zhang Zhi-min, and Su Xin,"Lightweight aluminum alloy material in the modern automotive manufacturing technology application," Special purpose vehicle.

[2] Chen You-jun,"A study on the development strategy of China-auto parts industry," CHINA AUTO. vol.4, pp.12-13, 2006.

[3] 3.D.G. Mallapur, K. Rajendra Udupa, and S.A. Kori, "Studies on the influence of grain refining and modification on microstructure and mechanical properties of forged A356 alloy,"Materials Science and Engineering A. vol.528, pp.4747-4752, 2011.

DOI: 10.1016/j.msea.2011.02.086

[4] X.H. Zhang, G.C.Su, C.W.Ju, W.C. Wang, and W.L. Yan, "Effect of modification treatment on the microstructure and mechanical properties of Al-0.35%Mg-7.0%Si cast alloy,"Materials and Design. vol.31, pp.4408-4413, 2010.

DOI: 10.1016/j.matdes.2010.04.032

[5] A.K. Prasada Rao, K.Das, B.S. Murty, and M.Chakraborty, "Al-Ti-C-Sr master alloy-A melt inoculant for simultaneous grain refinement and modification of hypoeutectic Al-Si alloys," Journal of Alloys and Compounds. vol.480, pp. L49-L51, 2009.

DOI: 10.1016/j.jallcom.2009.02.147

[6] Liu Ying, and Zeng Jian-jun, "RE and Sb Combination Modification of Al-7Si-0.3Mg Alloy,"Special Casting & Nonferrous Alloys. vol.28, pp.587-591, 2008.

[7] A.Knuutinen, K.Nogita, S.D.McDonald, and A.K. Dahle, "Modification of Al-Si alloys with Ba,Ca,Y and Yb,"Journal of Light Metals. vol.1, pp.229-240, 2001.

DOI: 10.1016/s1471-5317(02)00004-4

[8] L. Lu, and A.K. Dahle, "Effects of combined additions of Sr and AlTiB grain refiners in hypoeutectic Al-Si foundry alloys," Materials Science and Engineering A. vol.435, pp.288-296, 2006.

DOI: 10.1016/j.msea.2006.07.081

[9] D. G. Mallapur, S. A. Kori, and K. Rajendra Udupa, "Influence of Ti, B and Sr on the microstructure and mechanical properties of A356 alloy,"J Mater Sci. vol.46, pp.1622-1627, 2011.

DOI: 10.1007/s10853-010-4977-3

[10] M.Timpel, N.Wanderka, G.S. Vinod Kumar, and J.Banhart, "Microstructural investigation of Sr-modified Al-15wt%Si alloys in the range from micrometer to atomic scale," Ultramicroscopy. vol.111, pp.695-700, 2011.

DOI: 10.1016/j.ultramic.2010.12.023

[11] Hu Hui-fang, Li Hua-ji, Xue Han-song, and Kong Fan-xiao, "Mechanical Properties of Cast High Silicon Aluminum Piston Alloy at High Temperature Based on Orthogonal Regression Design," Special Casting & Nonferrous Alloys. vol.28, pp.314-315, 2008.

[12] Sergio Haro-Rodríguez, Rafael E. Goytia-Reyes, and Dheerendra Kumar Dwivedi, "On influence of Ti and Sr on microstructure, mechanical properties and quality index of cast eutectic Al-Si-Mg alloy," Materials and Design. vol.32, pp.1865-1871, 2011.

DOI: 10.1016/j.matdes.2010.12.012