Effects of solidification cooling rate on the corrosion resistance of a biodegradable β-TCP/Mg-Zn-Ca composite.

Biodegradable beta-tricalcium phosphate (β-TCP) particle reinforced magnesium metal matrix composites (Mg-MMC) have attracted increasing interest for application as implant materials. This investigation was conducted to study the effect of cooling rate on the microstructure and corrosion behavior of a biodegradable β-TCP/Mg-Zn-Ca composite. The composite was fabricated under a series of cooling rates using a wedge-shaped casting mold. The microstructure of the composite was examined by optical and scanning electron microscopy, and the corrosion behavior was investigated using an electrochemical workstation and immersion tests in a simulated body fluid (SBF). Faster cooling rates were shown to refine the secondary phase and grain size, and produce a more homogenous microstructure. The refined microstructure resulted in a more uniform distribution of β-TCP particles, which is believed to be beneficial in the formation of a stable and compact corrosion product layer, leading to improved corrosion resistance for the composite.