Tailoring microstructure and tensile properties of Mg-Si alloys varying solidification cooling rate and Si content

Abstract

Mg-Si alloys were investigated in terms of their microstructural characteristics and tensile properties, by varying solidification cooling rate and Si content. This type of investigation becomes essential since these alloys are considered potentially base alloys for new biocompatible and biodegradable materials that might be used to produce a variety of temporary implants. This because Silicon (Si) has been recognized as a vital mineral in the human body, aiding both the healing process and the development of the immune system. Despite these characteristics provided by Si, Mg-Si alloys typically have low ductility and tensile strength due to the presence of coarse Mg2Si particles. Therefore, efforts to understand and improve these properties are most welcome. In order to deepen the knowledge of these alloys, the present research analyzed three Mg-Si alloys: Mg-0.6 wt% Si, Mg-1.3 wt% Si and Mg-1.7 wt% Si regarding their microstructures and phase's morphologies produced in a broad range of solidification rates' samples and their corresponding tensile properties. The predominance of dendritic arrangement with the interdendritic region composed of the (Mg + Mg2Si) eutectic was noted for the Mg-0.6 wt% Si and Mg-1.7 wt% Si alloys. Eutectic cells prevailed for the Mg-1.3 wt% Si alloy, with cells varying from squarer and hexagonal to a more rounded shape with the decrease in cooling rate. Experimental influences of the microstructural parameters on the tensile properties have been verified. Except for the Mg-1.3 wt% Si alloy, the tensile properties of the other alloys were found to be roughly independent of the dendritic length scales in the verified ranges. In general, increased Si content led to a reduction in strength and ductility, probably due to the increase in the fraction of Mg2Si particles, which is an effective phase in the stress concentration during loading, shortening the break.