Investigation of the phase equilibria in the Sn-Bi-In alloy system

Abstract

This article presents an investigation of the phase equilibria in the Sn-Bi-In ternary alloy system, performed both by theoretical and experimental methods. Following the regular solution model and a standard thermochemical calculation, a theoretical evaluation of the phase equilibrium in the entire ternary system is conducted. The thermodynamic parameters required for the calculation are initially obtained by fitting the model to existing data available from prior studies. The theoretical results are then validated and further improved by experimental work in which alloys with several critical compositions were chosen and examined. In the experimental work, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and energy-dispersive X-ray (EDX) spectroscopy were jointly used to identify the transition temperatures and the phases in the microstructure. The resulting phase diagram agrees well both with the existing data and with the data from the current experiments. However, different from previous findings, this study finds a nonbinary nature of the Sn-BiIn and Sn-BiIn 2 quasi-binaries and nine invariant reactions, one eutectic, six peritectic and two peritectoid. The phase-reaction scheme (Scheil diagram), the liquidus projection, and the phase diagram, covering entire compositional ranges, are established.

Phase Equilibria in the Bi-In-Sn-Zn System. Thermal Analysis vs. Calculations

“…While the phase-transition temperatures are generally in agreement, the new phase diagram represents a different nature of the quasi-binaries, the number and type of the invariant reactions, and the reaction paths [23]. It is found that the Sn-BiIn and Sn-BiIn 2 quasi-binary systems are not pseudobinaries, which eventually leads to a phase diagram with only one eutectic reaction.…”

“…The phase diagram of the Bi-In-Sn ternary system was re-examined in the study of Yoon et al [23] and the calculated phase diagram has both similarities and dissimilarities to the previously determined one. While the phase-transition temperatures are generally in agreement, the new phase diagram represents a different nature of the quasi-binaries, the number and type of the invariant reactions, and the reaction paths [23].…”

“…[10] the univariant and invariant transitions were determined from onset temperatures and the liquidus from the last peak of DTA signal. The samples groups of numbers (23,25,27), (51, 53, 57) and (87, 89) were analyzed in 40-770 K (-233-497°C) temperature range with the heating and cooling rates of 2 deg/min in two consecutive cycles. Also the samples no.…”

“…In the case of the Bi-In-Sn system, the thermodynamic parameters were taken from the assessment of Yoon et al [23], with some later modification [7].…”

“…It is found that the Sn-BiIn and Sn-BiIn 2 quasi-binary systems are not pseudobinaries, which eventually leads to a phase diagram with only one eutectic reaction. Other invariant reactions (eight in total) are determined to be peritectic and peritectoid [23].…”