Effect of Pulsed Magnetic Field on Microstructure and Mechanical Properties of Eutectic Al-Si Alloy
- PDF / 720,061 Bytes
- 6 Pages / 593.972 x 792 pts Page_size
- 58 Downloads / 220 Views
CTION
OWING to the excellent properties, such as good abrasion and corrosion resistance, low thermal-expansion coefficient, high strength to weight ratio, and good castability, eutectic and near-eutectic Al-Si alloys have been widely used in automotive applications, especially for cylinder blocks and heads, pistons, and valve lifters.[1,2] The eutectic in the Al-Si alloys occur at about 12 wt pct Si, and the microstructure of eutectic Al-Si alloy should contain only the eutectic mixture (a-Al + eutectic silicon). In general, the mechanical properties of eutectic Al-Si alloy depend not only on the chemical composition but, more importantly, also on morphology and size of eutectic silicon. In unmodified eutectic Al-Si alloy, the main eutectic reaction occurs at 847.15 K (574 °C) as a binary reaction, which results in coarse irregular plate-like or needle-like eutectic silicon which is harmful to the mechanical properties of the eutectic Al-Si alloy.[3] The modification of eutectic silicon is being studied more extensively with increasing usage. Three well-known eutectic modification methods have been developed so far, namely, chemical modification,[4–6] quench modification,[7] and superheating modification.[8] The application of a pulsed magnetic field (PMF) in the solidification of metals is considered an effective method to refine grains and improve the mechanical properties of the metals, and it has been paid more attention in recent years. PMF process has several advantages such as simple equipment, high efficiency, low investment, extensive alloy application scope, as L. ZHANG, Lecturer, is with School of Aeronautical Manufacture Engineering, Nanchang Hangkong University, Nanchang, 330063, People’s Republic of China. Contact e-mail: [email protected] Manuscript submitted July 1, 2012. Article published online December 14, 2012. 390—VOLUME 44B, APRIL 2013
well as low pollution because of the noncontact with the melt.[9–11] Yang et al. applied PMF during the solidification of Mg-Al-Zn alloys and Al-Cu alloys, and the grain refinement was achieved with proper thermal control under the action of PMF.[11,12] Although the effect of PMF on the solidification of metals has been studied extensively, to the best of our knowledge, the effect of PMF on eutectic silicon structure has not been investigated. Moreover, few studies have referred to the effect of PMF on the mechanical properties.[12] Therefore, in the current study, the effect of PMF on microstructure and mechanical properties of eutectic Al-Si alloy were studied.
II.
EXPERIMENTAL PROCEDURES
Al-12.4Si alloy was prepared using the commercialpurity Al and Al-20Si master alloy (all composition quoted in the current study, in mass pct unless otherwise stated). The composition of the Al-12.4Si alloy was assessed using atomic absorption spectrometer (VARIAN-AA240, Netherlands), and is shown in Table I. The experiment was carried out by using a self-developed PMF solidification apparatus, and a sketch map of the experimental solidification apparatus is shown in Figure 1. In the equivalent
Data Loading...
