Experimental investigation and thermodynamic calculation of the phase equilibria in the Cu-Sn and Cu-Sn-Mn systems

Abstract

The phase equilibria in the Cu-rich portion of the Cu-Sn binary and Cu-Sn-Mn ternary systems have been determined using the diffusion-couple method, differential scanning calorimetry (DSC), high-temperature electron diffraction (HTED), and high-temperature X-ray diffraction (HTXRD) techniques. The present experimental results on the binary Cu-Sn system show the presence of the two-stage, second-order reaction in the bcc-phase region, rather than a two-phase equilibrium between the disordered bcc (A2) and the ordered bcc (D0 3 ) phases, as reported before. Phase equilibria in the Cu-Sn-Mn ternary system in the composition range of 0 to 30 at. pct Sn and 0 to 30 at. pct Mn at 550 °C, 600 °C, 650 °C, and 700 °C have been determined, and a ternary compound (Cu 4 MnSn) with a very small solubility has been detected. A thermodynamic analysis of the Cu-Sn-Mn ternary system including the Cu-Sn and Mn-Sn binary systems has also been carried out by the CALPHAD (Calculation of Phase Diagrams) method, in which the Gibbs energy of the bcc phase is described by the two-sublattice model in order to take into account the second-order A2/B2 ordering reaction. A consistent set of optimized thermodynamic parameters for the Cu-Sn-Mn system for describing the Gibbs energy of each phase results in a better fit between calculation and experiment.A2 → B2 → D0 3

Corrigendum to “Application of single pan thermal analysis to Cu–Sn peritectic alloys” [Acta Mater 56 (2008) 1519–1528]

“…Therefore, this transformation is most likely attributed to a second-order ordering reaction of the peritectic phase occurring during solidification. These measurements favor the Cu-Sn phase diagram of Liu et al [2]. …”

“…A close comparison with a microsegregation model that included back-diffusion in the primary a-solid phase allowed us to validate successfully the heat flow model. SPTA on Cu-Sn alloys have shown that the CuSn phase diagram recently reinvestigated in Liu et al's review [2] is the most reliable. Obviously, the thermal analysis method developed here can be used for other metals and alloys.…”

“…Two solid-state phase transformations have been measured: at 579.2°C, a very small bump on T S revealed the presence of a probable second-order reaction. Looking at the recent Cu-Sn phase diagram from Liu et al [2] (Fig. 6), this reaction has been attributed to the ordering reaction of the bphase, where it transforms from a disordered A2 structure to an ordered DO3 structure.…”

“…Furthermore, the Cu-Sn phase diagram found in most metals handbooks is based on thermal analyses and metallographic observations performed before 1970 [1]. Only recently have the phase equilibria in the Cu-rich portion of the system been thoroughly reinvestigated by Liu et al [2] using diffusion-couple, differential scanning calorimetry, high-temperature electron diffraction and high-temperature X-ray diffraction techniques. These authors reassessed the Cu-Sn phase diagram for temperatures below the peritectic reaction a þ liquid !…”

Application of single pan thermal analysis to Cu–Sn peritectic alloys

“…For a clear phase identification, concentration measurements have also been carried out using a microprobe. Finally, the observed solidification paths have been compared with the Cu-Sn phase diagram of Liu et al [2].…”