Enhancement of TiB Grain Refining Effect on A356 Gravity Die Casting with the Addition of Yttrium

Lim Ying Pio, Wang Chan Chin

Departmentof Mechanical Engineering, Universiti Tunku Abdul Rahman, Kuala Lumpur, Malaysia.

DOI: 10.4236/msa.2012.310104                

Abstract

The present work investigates the effect yttrium on the grain refining efficiency of Al-5Ti-1B in gravity die cast A356 aluminum alloy. A series of casting experiments were carried out in which the Ti and B contents were maintained constantly at 0.1 and 0.02 wt% respectively. The inoculation level of yttrium was manipulated at the amount of 0, 0.1, 0.2, 0.3, 0.4 and 0.5 wt%. Microstructural characterization of the as-cast A356 alloy was investigated by means of optical microscope and its phases are detected by XRD. XRF is used to determine the contents of inoculating elements such as Ti, B and Y so that their actual optimal ratio in the casting can be approximated. The mechanical properties tested are tensile strength and hardness. The inoculation of yttrium was found to enhance the grain refinement effect of Al-5Ti-1B grain refiner and improve the mechanical properties. The optimal weight percentage of yttrium was discovered to be 0.3. The grain refining efficiency of combining yttrium and Al-5Ti-1B on A356 aluminum alloy was mainly attributed to the heterogeneous nucleation of TiB₂ and TiAl₃ particles which were dispersed more evenly in the presence of yttrium and also as a result of α-Al grain growth restriction by AlY₃compound precipitated at grain boundaries during solidification.

Keywords

Al-5Ti-1B Grain Refiner; Gravity Dies Casting; Mechanical Testing; Microstructure; XRD; XRF; Yttrium

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	A. K. Prasada Rao, K. Das, B. S. Murty and M. Chakra- Borty, “Microstructural Features of As-Cast A356 Alloy Inoculated with Sr, Sb Modifiers and Al-Ti-C Grain Refiner Simultaneously,” Materials Letters, Vol. 62, No. 2, 2008, pp. 273-275. doi:10.1016/j.matlet.2007.05.020
[2]	H. L. Zhao, H. L. Baia, W. G. Jun and S. K. Guana, “Preparation of Al-Ti-C-Sr Master Alloys and Their Refining Efficiency on A356 Alloy,” Materials Characterization, Vol. 60, No. 5, 2009, pp. 377-383. doi:10.1016/j.matchar.2008.10.012
[3]	R. Prasada, A. K. Das, K. Murty and B. S. Chakraborty, “On the Modificationand Segregation Behavior of Sb in Al-7Si Alloy during Solidification,” Materials Letters, Vol. 62, No. 12-13, 2007, pp. 2013-2016.
[4]	B. Chalmers, “The Structure of Ingots,” Journal of the Australian Institute of Metals, Vol. 8, 1963, pp. 255-263.
[5]	S. A. Metz and M. C. Flemings, “A Fundamental Study of Hot Tearing,” The Merton C. Flemings Symposium on Solidification and Materials Processing, USA Publishers, Cambridge, 2000, pp. 181-188.
[6]	D. Apelian, G. K. Sigworth and K. R. Whaler, “Assessment of Grain Refinement and Modification of Al-Si Foundry Alloys by Thermal Analysis,” AFS Transactions, Vol. 92, 1984, pp. 297-307.
[7]	D.G. McCartney, “Grain Refining of Aluminium and Its Alloys Using Inoculants,” International Materials Reviews, Vol. 34, 1989, pp. 247-260.
[8]	J. A. Spittle, J. M. Keeble and M. A. Meshhedani, “The Grain Refinement of Al-Si Foundry Alloys,” Light Metals, 1997, pp. 795-800.
[9]	W. S. Miller, L. Zhuang, J. Bottema, et al., “Recent Development in Aluminum Alloys for the Automotive Industry,” Materials Science and Engineering, Vol. 280, No. 1, 2000, pp. 37-49. doi:10.1016/S0921-5093(99)00653-X
[10]	Y. Birol, “Grain Refining Efficiency of Al-Ti-C Alloys,” Journal of Alloys and Compounds, Vol. 422, No. 1-2, 2006, pp. 128-131. doi:10.1016/j.jallcom.2005.11.059
[11]	W. O. Ngalaa and H. J. Maier, “Creep-Fatigue Interaction of the ODS Superalloy: PM 1000,” Materials Science and Engineering A, Vol. 510-511, 2009, pp. 429-433.doi:10.1016/j.msea.2008.06.056
[12]	P. J. Zhou, J. J. Yu and X. F. Sun, “Role of Yttrium in the Microstructure and Mechanical Properties of a Boron- Modified Nickel-Based Superalloy,” Scripta Materialia, Vol. 57, No. 7, 2007, pp. 643-646. doi:10.1016/j.scriptamat.2007.06.003
[13]	H. Z. Li, X. P. Liang and F. F. Li, “Effect of Y Content on Microstructure and Mechanical Properties of 2519 Aluminum Alloy,” Transaction of Nonferrous Metals Society of China, Vol. 17, No. 6, 2007, pp. 1194-1198.doi:10.1016/S1003-6326(07)60248-9
[14]	“Heat Treating, Metals Handbook,” 9th Edition, ASM International, Metals Park, Vol. 4, 1981.
[15]	C. X. Xu, B. F. Lu and Z. L. Lü, “Grain Refinement of AZ31 Magnesium Alloy by Al-Ti-C-Y Master Alloy,” Journal of Rare Earths, Vol. 26, No. 4, 2008, pp. 604- 608. doi:10.1016/S1002-0721(08)60146-5
[16]	Y. Y. Chen, Y. F. Si and F. T. Kong, “Effects of Yttrium on Microstructures and Properties of Ti-17Al-27Nb Alloy,” Transaction of Nonferrous Metals Society of China, Vol. 16, No. 2, 2006, pp. 316-320. doi:10.1016/S1003-6326(06)60054-X