Microstructural evolution of the amorphous layers on Mg-Zn-Ca alloy during laser remelting process

Abstract

Mg-Zn-Ca bulk metallic glasses (BMGs) have been regarded as new biodegradable materials for orthopedic implants, while size constrains limit their biomedical applications. In this study, Mg-based amorphous layers with the nominal composition of Mg65Zn30Ca5 have been successfully produced using the laser remelting method. The influences of laser scanning speed on the microstructural characteristics of Mg-Zn-Ca amorphous layers during laser remelting process were investigated systematically by experiments and numerical simulations. Amorphous phase could be formed when the laser scanning speed was kept above 1000 mm/min. The remelted layer mainly consisted of a gradient structure: amorphous-crystalline composite layer, transitional layer and crystalline substrate. The increase of the laser scanning speed was benefit to improve the corrosion resistance of the remelted layer due to the formation of amorphous structure. Analysis of the temperature distributions and related thermal profiles simulated using the finite element method indicated that the crystallization could be suppressed with the increase of the laser scanning speed, which would shorten the residence time and leads to higher cooling rate in this process as well.