# Quaternary Zinc Alloys with Magnesium, Calcium and Strontium after Hydrostatic Extrusion—Microstructure and Its Impact on Mechanical and Corrosion Properties

## TL;DR

This paper studies a new zinc alloy with magnesium, calcium, and strontium to improve mechanical and corrosion properties for bioabsorbable implants.

## Contribution

A quaternary Zn alloy with Mg, Ca, and Sr is developed and processed via hydrostatic extrusion to enhance mechanical and corrosion properties.

## Key findings

- The alloy's microstructure includes α-Zn grains and intermetallic phases like Mg2Zn11, CaZn13, and SrZn13.
- Hydrostatic extrusion improved mechanical properties and uniform corrosion resistance in Hanks’ solution.
- SEM and XRD analysis confirmed the microstructure's impact on performance.

## Abstract

The development of bioabsorbable implants from Zn alloys is one of the main interests in the new generation of biomaterials. The main drawbacks of Zn-based materials are their insufficient mechanical properties. In the presented studies, a quaternary alloy composed of zinc with magnesium (0.2–1 wt. %), calcium (0.1–0.5 wt. %) and strontium (0.05–0.5 wt. %) was prepared by gravity casting followed by hot extrusion and then by hydrostatic extrusion. Microstructural characterization using scanning electron microscopy (SEM) and X-ray diffraction (XRD) phase analysis was performed. The mechanical properties were examined, using static tensile tests. Corrosion properties were analyzed using immersion tests. Samples were immersed in Hanks’ solution (temperature = 37 °C, pH = 7.4) for 14 days. All alloys were subjected after corrosion to SEM observations on the surface and cross-section. The corrosion rate was also calculated. The microstructure of the investigated quaternary alloy consists of the α-Zn grains and intermetallic phases Mg2Zn11, CaZn13 and SrZn13 with different grain sizes and distribution, which impacted both mechanical and corrosion properties. Thanks to the alloying by the addition of Mg, Ca, and Sr and plastic deformation using hydrostatic extrusion, outstanding mechanical properties were obtained along with improvement in uniformity of corrosion rate.