• The first application of ultrasonic treatment (UST) for microstructure refinement in biodegradable Zn alloy. • UST processing eliminated the cracked and segregated CaZn 13 phase in Zn-Cu-Ca alloy after hot rolling. • The UST-processed Zn-Cu-Ca alloy indicated improved mechanical properties. • The corrosion of UST-Zn-Cu-Ca alloy is more uniform than the non-UST counterpart under the similar corrosion rate. • The uniform degradation mechanism favour the strength retention of UST-Zn-Cu-Ca alloy in vitro . Zn-1.0Cu-0.5Ca (TA15) alloy has shown promising characteristics of enhanced mechanical properties and biodegradability for absorbable cardiovascular stents, endovascular devices, and wound closure devices applications. In this study, the TA15 alloy for bioabsorbable biomedical applications is investigated. In the conventionally cast TA15 (TA15-C) alloy, CaZn 13 phase are present as a large dendritic network with an average size of 73.25 ± 112.84 μm. Hot rolling of the TA15-C alloy has broken the long and dendritic network of the CaZn13 phases, however, the refined phases are observed as segregations and the distribution is non-uniform. These segregated CaZn 13 suffered heavy localised corrosion which lead to poor mechanical properties in the as-fabricated condition and after biodegradation. Ultrasonic treatment (UST) during casting is identified as an effective technique for the refinement and redistribution of CaZn 13 particles in TA15 alloy, which successfully reduce the size of the CaZn 13 phase to 10.91 ± 4.65 μm in the as-solidified condition. After hot rolling, the UST processed TA15 (TA15-UST) shows improved mechanical properties due to grain refinement and the reduction in microstructural defects, i.e. the broken CaZn 13 phase. Results of 8-week immersion corrosion tests showed that both alloys possess very similar corrosion rate. However, TA15-UST has markedly improved corrosion homogeneity compared to TA15-N which favours the retention of mechanical properties even after prolonged exposure to physiological fluids.