Effects of GD on microstructure and corrosion properties of Mg-4Zn alloy

Abstract

This work explores the multifaceted impact of gadolinium (Gd) on the microstructure and corrosion properties of a Mg-4Zn alloy, with implications for lightweight material applications. In recent years, magnesium (Mg) alloys have gained prominence in industries such as automotive and aerospace due to their favorable strength-to-weight ratios. Addition of zinc (Zn) and Gd presents a promising avenue for improving mechanical and corrosion properties.The addition of Gd can significantly alter the corrosion behavior of the alloy. Corrosion in Mg alloys is a critical concern, particularly in aggressive environments. This investigation commences with a systematic variation of Gd content in the Mg-4Zn alloy, ranging from 1% to 3%. Microstructural changes are meticulously examined through optical and scanning electron microscopy (SEM), elucidating Gd’srole in grain refinement, phase transformation and forming long-period stacking ordered (LPSO) phases. SEM images reveal distinct microstructural alterations at varying Gd concentrations. Comprehensive corrosion analysis encompasses electrochemical techniques and immersion tests in corrosive environments. These analyses unveil a clear correlation between Gd content and corrosion resistance, shedding light on the alloy's suitability for applications in aggressive environments such as marine or automotive settings. XRF analysis verified the chemical composition of the alloys and XRD analysis showed the peaks of phases containing Gd with Mg-Zn alloys at certain angles. The SEM analysis shows the presence of LPSO structures in the microstructures which lead to form a protective layer to decrease corrosion. The presence of Gd enhances the formation of this layer. The hardness of the alloy with 3% Gd is the highest among all three specimens. The electrochemical test demonstrates that the positive breakdown voltage reduces from -1.25 V for 1% Gd to -1.18 V for 3% Gd stating the corrosion reduction due to more Gd content. The corroded surface exhibits several micro cracks in the corroded zones in the surface and the amount is very less when the Gd content is higher. The results emphasize Gd's effectiveness as an alloying element, not only refining the grain structure but also significantly retarding corrosion propagation. The research findings demonstrate that these Gd-modified Mg-4Zn alloys hold great promise as lightweight, corrosion-resistant materials.