  The eutectic Ga-In (EGaIn) alloy has low vapor pressure, low toxicity, high
thermal and electrical conductivities, and thus has shown a great potential for
smart material applications. For such applications, EGaIn is maintained above
its melting point, below which it undergoes solidification and phase
separation. A scientific understanding of the structural and compositional
evolution during thermal cycling could help further assess the application
range of low-melting-point fusible alloys. Here, we use an integrated suite of
cryogenically-enabled advanced microscopy & microanalysis to better understand
phase separation and (re)mixing processes in EGaIn. We reveal an overlooked
thermal-stimulus-response behaviour for frozen mesoscale EGaIn at cryogenic
temperatures, with a sudden volume expansion observed during in-situ
heat-cycling, associated with the immiscibility between Ga and In during
cooling and the formation of metastable Ga phases. These results emphasize the
importance of the kinetics of rejuvenation, and open new paths for EGaIn as a
self-healing material.
