Phase Identification of Cu-In Alloys with 45 and 41.25 at.% In Compositions

Abstract

In this work, the thermal stability of Cu-In alloys with 45.0 and 41.2 at.% In nominal compositions was investigated by differential scanning calorimetry (DSC), scanning electron microscopy, wavelength dispersive spectroscopy, and in-situ synchrotron x-ray powder diffraction (S-PXRD) over a temperature range from 25 up to 400 °C. The studied samples are mainly composed of a Cu₁₁In₉ phase together with minor amounts of the B phase (based on the NiAs-Ni₂In type structure) and, in one of the samples, with a minor amount of pure In. No evidence of the Cu₁₀In₇ (41.2 at.% In) phase was detected, not even in the sample with 41.2 at.% In nominal overall composition. The combined use of the S-PXRD and DSC techniques allowed us to identify two phase transitions involving the Cu₁₁In₉ phase, one of them corresponding to the $\upeta^{\prime} \rightleftharpoons {\text{B}} + {\text{Cu}}_{11} {\text{In}}_{9}$ reaction at T = 290 °C and the other to the peritectic $\upeta^{\prime} + {\text{L}} \rightleftharpoons {\text{Cu}}_{11} {\text{In}}_{9}$ reaction at T = 311 °C.