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

Abstract

Single pan thermal analyses (SPTA) have been performed on Cu-14.5 wt.% Sn, Cu-21.3 wt.% Sn and Cu-26.8 wt.% Sn peritectic alloys. For this purpose, a SPTA assembly has been built and calibrated. As the latent heat is a function of temperature and composition during solidification of alloys, a new heat flow model coupled to a Cu-Sn thermodynamic database has been defined for the calculation of the corresponding evolutions of the solid mass fraction, f s ðT Þ. To verify the accuracy of this model, a close comparison with a microsegregation model that includes back-diffusion in the primary a-solid phase has also been conducted successfully. The thermal analyses have finally shown that the Cu-Sn phase diagram recently assessed in the review of Liu et al. is the most reliable.

Peritectic solidification of Cu–Sn alloys: Microstructural competition at low speed

“…10, the obtained solvus lines and the extrapolated equilibrium compositions C a and C p at T p differ from the Cu-Sn phase diagram defined in Section 3. However, substantial differences also exist between the various phase diagrams reported in the literature [32].…”

“…This is due to the particular shape of the Cu-Sn phase diagram, which shows a decreasing DT ). An important issue must be addressed here: for all DS experiments, two solid-state phase transformations have been identified for the b-phase: (i) the quench induced a partial decomposition of the b-phase into an acicular martensitic microstructure for compositions between about 22 and 24 wt.% Sn, thus preventing its indexing during EBSD analyses; and (ii) in agreement with single pan thermal analyses made on Cu-Sn alloys [32], the b-phase also transformed to an a + d lamellar structure via a eutectoid reaction for temperatures below 520 ± 5°C. .…”

“…b varies between 795.7 and 798°C and the equilibrium concentrations C a , C p and C L are not defined accurately. In a recent publication [32], single pan thermal analyses performed on Cu-Sn alloys revealed that the phase diagram reinvestigated by Liu et al [31] is the most reliable, even if the peritectic temperature and the corresponding equilibrium concentrations are not assessed accurately.…”

EBSD: a powerful microstructure analysis technique in the field of solidification

“…7). In this system, the α phase has an fcc structure, whereas the crystallographic structure of β is bcc but exhibits solid‐state transformations (Cortie & Mavrocordatos, 1991; Liu et al , 2004; Kohler, 2008; Kohler et al , 2008). As can be seen in Fig.…”

Determination of the thermophysical properties of a CuCr1Zr alloy from liquid state down to room temperature

“…Contrary to Differential Thermal Analysis (DTA), SPTA permits the analysis of a huge volume of metal (cm 3 order), thus reducing the effect of nucleation undercooling. Details of this method are available elsewhere [7]. The experiments are conducted with a cylindrical sample (diameter 13.8 mm, height 15 mm) using a high purity gas to minimise oxidation.…”