Impact of spherulite-type crystalline defects on the mechanical and electrochemical properties of Ti40Cu36Zr10Pd14 metallic glasses

Abstract

One of the limitations to the use of certain bulk metallic glasses is related to the formation of crystalline zones or defects, often called “spherulites”, during the casting process. In the case of Ti40Zr10Cu36Pd14 (at%) metallic glass, which is a candidate for biomedical applications, spherulites of diameter up to few hundreds of microns were previously reported, but their crystallographic features and their role in the mechanical behavior and the corrosion resistance remains to be determined.In this work, a detailed description of the microstructure of spherulites is provided. Tensile, compression and fatigue tests were carried out. In addition, corrosion behavior was studied by global and local electrochemical measurements. The spherulites have a deleterious effect on the tensile and fatigue strength of the alloy, even if it still retains strength properties that are far superior to conventional crystalline materials. The electrochemical studies do not show any difference in potential between the spherulite and the amorphous matrix, which indicates that the presence of spherulites is probably not the direct cause of the pitting phenomenon observed, which is unfortunately a clear drawback of this alloy when considering biomedical implants.