Materials Science and Engineering A 393 (2005) 109–117 Silicon morphology modification in the eutectic Al–Si alloy using mechanical mold vibration Numan Abu-Dheir, Marwan Khraisheh ∗ , Kozo Saito, Alan Male Center for Manufacturing and Department of Mechanical Engineering, University of Kentucky, Lexington, KY 40506-0108, USA Received 16 August 2004; received in revised form 24 September 2004; accepted 27 September 2004 Abstract It is well documented that applying mechanical vibration to the mold during solidification has a profound effect on the microstructure and mechanical properties of castings. However, it is still not well understood how mechanical vibration change the resulting microstructure. Most of the available studies are qualitative and provide little quantitative information that can be used by the casting industry. In this work, mechanical mold vibration is applied to an Al–Si eutectic (Al–12.5% Si) alloy at a frequency of 100 Hz and variable amplitudes in the range of 18–199 m. It is shown that the silicon morphology was strongly influenced by the level of vibration amplitude. Generally, increasing the vibration amplitude tends to reduce the lamellar spacing and change the silicon morphology to become more fibrous. However, exceeding a critical value of vibration amplitude tends to coarsen the silicon. The corresponding changes in mechanical properties are also investigated. It is shown that the maximum elongation is more influenced by vibration than the tensile strength for the range of conditions tested here. © 2004 Elsevier B.V. All rights reserved. Keywords: Casting; Mold vibration; Microstructure modification; Al–Si alloy 1. Introduction Controlling the microstructure that results from the cast- ing process is considered one of the main challenges faced by today’s foundry industry. The challenge is to produce defect- free metallic components that demonstrate optimal mechan- ical properties with the lowest cost and shortest lead-time. Fine equiaxed microstructures generally exhibit favorable mechanical properties of strength and ductility with low sus- ceptibility to microporosity and cracks. It is a common practice in industry to refine the microstruc- ture through the application of post processing techniques, e.g. heat treatment, rolling, etc. However, in-situ casting treat- ment for refining the microstructure provides a big advan- tage from the point of view of cost reduction. Several prac- ∗ Corresponding author. Tel.: +1 859 257 6262x219; fax: +1 859 323 1035. E-mail addresses: anuma0@engr.uky.edu (N. Abu-Dheir), khraisheh@engr.uky.edu (M. Khraisheh), saito@engr.uky.edu (K. Saito), atmale@engr.uky.edu (A. Male). tices are currently used during the casting process to pro- duce this microstructure. These method include rapid cool- ing [1], adding grain refiners [2,3], and rheocasting [4,5]. All of these techniques have proved successful in produc- ing equiaxed grains; however each has several associated disadvantages. Rapid cooling may produce cracking and it is not suitable for thin-section castings. Adding grain refin- ers may be harmful to the environment, and involves prob- lems like fading and poisoning [6–7]. Rheocasting, in spite of its discovery thirty years ago, still lacks the popularity that was anticipated. This is mainly due to the high cost associated with the preparation of the material appropriate for rheocasting and the resulting long lead-time. Subject- ing the solidifying melt to vibration has also proved suc- cessful in refining the microstructure. However, the lack of quantitative conclusive correlation between vibration param- eters and the resulting refinement has prevented this tech- nique from being more widely used. There are also other issues representing challenges to the application of vibra- tion as a refinement technique. These include the applica- bility to large castings, effect of initial mold temperature 0921-5093/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2004.09.038