H. Kaya 1 , S. Engin 2 , E.Çadırlı 3 , U. Böyük 1 , N. Maraşlı 2

1. (a) (b) b a Electrical Properties As a Function of Solidification Parameters of Bismuth-Tin-Silver Eutectic Alloy H. Kaya1, S. Engin2, E.Çadırlı3, U. Böyük1, N. Maraşlı2 1Erciyes University, Department of Science Education, Kayseri, Turkey, 2 Erciyes University, Department of Physics, Kayseri, Turkey , 2Erciyes University, Department of Physics, Niğde, Turkey, 3.Experimental Results Measured values of electrical resistivity dependence on the values of G and V are given in Fig. 3. 1. Introduction Unidirectional solidification of eutectic alloys has received considerable attention in the past few years because the alignment of fibers or plates in some of these eutectics produces attractive directional physical or mechanical properties. Most of the work has been done on binary alloys of eutectic and near eutectic compositions, and only recently work has been initiated in the area of ternary eutectic alloys. The development of lead-free solders has emerged as one of the key issues in the electronics packaging industries. Bi-Sn-Ag ternary alloy has been considered as one of the lead-free solder materials that can toxic solders without increasing soldering soldering temperature. This study investigates the effect of temperature gradient and growth rate on the elecritical properties of the Bi-43.47 wt.% Sn-0.68 wt.% Ag alloy. 2. Experimental Procedure 2.1 Solidification and microstructures Bi-Sn-Ag alloy was directionally solidified upward with different growth rates (V=6.6-132.8 mm/s) at a constant temperature gradient (G=2.3 K/mm) and with different temperature gradients (G=2.3-5.7 K/mm) at a constant growth rate (V=13.2 mm/s) using a Bridgman–type growth apparatus (Fig. 1). The quenched samples were removed from the graphite crucible and the metallographic process, the microstructures of the samples were revealed (Fig. 2). 2.2. Measurement of the electrical resistivity The electrical resistivity strongly depends on temperature. In metals, electrical resistivity increases with increasing temperature. The dependence of electrical resistivity on the temperature is often expressed as a slope in the electrical resistivity versus temperature graph. The dependence of the electrical resistivity on solidification parameters and temperature were analyzed. Variations of r with solidification processing parameters and the microstructure parameter are plotted and shown in Fig. 3. Figure 3. (a) Variation of electrical resistivity as a function temperature gradients. (b) Variation of electrical resistivity as a function growth rates 4. Conclusions In present work, the influence temperature and solidificationprocessing parameterson themechanical properties of Sn- Bi-Ag ternary alloy were investigated.Theresults aresummarized as follows: The values of r have been measured on the directionally solidified samples. It was found that the values of r increase with increasing the values of G and V. The establishment of the relationships among r, G and V can be given as; r=8.6x10-6G0.05 and r=11.6x10-6 V0.09. Figure 1. (a) Block diagram of the experimental setup (b) The details of the Bridgman type directional solidification furnace. • References • K.W. Richter, H. Ipser, Intermetallics 11 (2003) 101. • M. Gündüz, H. Kaya, E. Çadırlı and A. Özmen, Mat. Sci. Eng. A 369 (2004) 215. • H. Kaya, U. Böyük, E. Çadırlı, N. Maraşlı, Kovove Mater. 48(5) (2010) 291. • Kaya H., Çadırlı E., Gündüz M. and Ülgen A. J. Mat. Eng. and Perf., 12(5),544–551. • H. Kaya, U. Böyük, E. Çadırlı, N. Maraşlı, Materials and Design,in press (2011). • R. Brandt, G. Neuer, Int J Thermophys 28 (2007) 1429–1446. Figure 2. Typical optical images of the growth morphologies of directionally solidified Sn-Bi-Ag eutectic alloy on transverse section (a): G=2.33 K/mm, V=13.25 mm/s and (b) G=2.33 K/mm, V=132.83 mm/s.