Microstructural Grading of Al-11 wt.%Mg2Si Hypoeutectic Alloy by Centrifugal Casting

Subject Areas : journal of New Materials

حجت اله امرایی ¹ (دانشجوی کارشناسی ارشد مهندسی مواد دانشگاه صنعتی سهند)
احد صمدی ² (استادیار مهندسی مواد دانشگاه صنعتی سهند)
اکبر وجد ³ (دانشجوی کارشناسی ارشد مهندسی مواد دانشگاه صنعتی سهند)

Received: 2015-12-30 Accepted : 2015-12-30 Published : 2010-09-23

Keywords: Functionally graded materials, hypoeutectic Al-11wt.%Mg2Si alloy, centrifugal casting, graded microstructure,

Abstract :

Centrifugal casting as a high capable technique has been frequently used for production of high performance castings. In two decades its capabilities has been progressed towards the production of cast components with functionally graded microstructures. A controlled attribution of the centrifugal force in this technique can cause a desirable grading of the microstructures hence properties in different sections of the castings. In this research, functionally graded Al-11wt.%Mg₂Si hypoeutectic alloy with graded distribution of α-Al phase was cast as a cylindrical specimen using the centrifugal casting. During the solidification, the initially formed α-Al grains due to the higher density in compared with the remained melt, were segregated in the centrifugal force direction. The microstructural observations reveal two distinguished layers in radial direction of the cast cylinder: the outer layer with a higher volume fraction of α-Al grains and the inner one with the eutectic structure. To modify the cast structure hence mechanical properties, the cast sample was subjected under solution and ageing heat treatments. The microstructural observations of the heat treated sample shows no noticeable change in the cast graded microstructure; however the eutectic structure was distorted from laminar to a fine dot-like structure. This minor microstructural evolution is accompanied with an increase in hardness of different sections of the sample.

References:



[1] Yan-bo, Z., Chang-ming, L., Kai, W., Mao-hua, Z., Yong, X. 2010. Characteristics of two Al based functionally gradient composites reinforced by primary Si particles and Si/in situ Mg₂Si particles in centrifugal casting. Trans. Nonferrous Met. Soc. China. 20: 361-370.

[2] Rajan, TPD., Pillai, RM., Pai, BC. 2008. Functionally graded Al-Al₃Ni in situ intermetallic composites: Fabrication and microstructural characterization. Journal of Alloys and Compounds. 453: L4-L7.

[3] Ogawa, T., Watanabe, Y., Sato, H., Kim, I., Fukui, Y. 2006. Theoretical study on fabrication of functionally graded material with density gradient by a centrifugal solid-particle method. Composites: Part A. 37: 2194-2200.

[4] Zhang, J., Wang, Y., Zhou, B., Wu, X. 1998. Functionally Graded Al/Mg₂Si In-situ Composites Prepared by Centrifugal Casting. Journal of Materials Science Letters. 17: 1677-1679.

[5] Chen, W., Wang, Q., Zai, C., Ma, C., Zhu, Y., He, W. 2001. Functionally graded Zn-Al-Si in-situ composites fabricated by centrifugal casting. Journal of Materials Science Letters. 20: 823-826.

[6] Wang, Q., Wei, Y., Chen, W., Zhu, Y., Ma, C., Ding, W. 2003. In situ surface composites of (Mg₂Si+Si)/ZA27 fabricated by centrifugal casting. Materials Letters. 57: 3851-3858.

[7] Zhang, J., Fan, Z., Wang, Y., Zhou, B. 2000. Hypereutectic aluminium alloy tubes with graded distribution of Mg₂Si particles prepared by centrifugal casting. Materials and Design. 21: 149-153.

[8] Qudong, W., Yongjun, C., Wenzhou, C., Yinhong, W., Chunquan, Z., Wenjiang, D. 2005. Centrifugally cast Zn-27Al-xMg-ySi alloys and their in situ (Mg₂Si + Si)/ZA27 composites. Materials Science and Engineering A. 394: 425-434.