Crystallization kinetics and microstructural analysis of lanthanum-modified zinc alloys

The development of functional engineering materials based on non-ferrous metals has progressed in recent years, and the incorporation of rare earth metals is a key strategy aimed at modifying the structural components of alloys to enhance their mechanical properties. The work presented herein investigates the effect of lanthanum addition on the microstructure and type of phases formed during crystallization. The effects of alloying elements on the solidification derivative curve and the monotectoid solid-state transformation of ZnAl10Cu1 alloys are also discussed. The overall impact of lanthanum addition was determined based on studies of the microstructure morphology, phase composition, and changes in the derivation curves of the studied alloys. Optical microscopy, scanning electron microscopy, and transmission electron microscopy were employed for structural analysis, and thermal-derivative analysis (TDA) was used to investigate the phenomena occurring during solidification in hypereutectic zinc alloys with various chemical compositions The results of this study indicate that the addition of La modifies the derivation curve during solidification by changing the morphology of the α phase and decreasing the monotectoid transformation temperature (α→α’). The presence of the Zn₅La phase in the a′ + η eutectics was also confirmed.