Mechanical and corrosion characteristics of micro-arc oxidized magnesium alloy (ZE41) friction stir welds in modified SBF

Abstract

Magnesium is a popularly known class of biodegradable metallic biomaterials, and it has spent most of its time in corrosion environments that must be validated before it can be used in real bio applications. This work studies the adaptability of rare earth magnesium alloy (Mg-RE) ZE41 welds for in vitro bio applications. Magnesium rare earth ZE41 alloy plates were welded through a friction stir joining process. The fabrication of a defect-free and strong friction stir butt joint was confirmed by microscopic analysis and mechanical tests. The joint efficiency of 79.25% was arrived from the tensile test based on ultimate tensile strength (UTS). The microhardness at WN, HAZ and base material were measured as 82, 63, and 70 respectively. A silicate electrolyte-based micro-arc oxidation (MAO) coating process was carried out on base and weld samples to study the corrosion behaviour of uncoated and coated samples in modified simulated body fluid (m-SBF). The average coating thickness of the samples was 40 µm. Then the processed samples were immersed in the m-SBF solution for 0.25 h, 72 h, and 168 h, and the degradation behaviour of all the samples was studied. The surface morphology and compositions were analysed through X-Ray diffraction and field emission scanning electron microscopy (FE-SEM) on all the MAO-coated and uncoated bases as well as weld samples. The electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation (PDP) tests were employed to evaluate the electro-chemical induced corrosion behaviour of the samples. The results revealed that MAO-coated ZE41 welded samples have better corrosion mitigation properties with a corrosion rate of 12.45 mpy after 168h of immersion than all other counterparts due to the compact oxide layer formation and further apatite mineral phase deposition that helps to delay the surface degradation of friction stir welded ZE41.

A surface and corrosion characterisation of micro arc oxidation treated friction stir welded ZM21 and ZE41 magnesium alloy: a comparison study

“…It was found that the weld samples exhibited lower yield and tensile strengths as compared to the base material samples. The variation in tensile strengths was attributed to the inclusion of different phases of non-homogeneity in the structure because of plastic deformation [34]. During tensile tests, tensile failures occurred in the heat-affected zone (HAZ) of the weld samples, and similar trends were reported in related studies.…”

“…Furthermore, it can be deduced from the EIS studies that the SZ of the FSW joint displayed better corrosion resistance properties compared to the corrosion resistance of the base metal in both the untreated and MAO-treated conditions. The enhanced corrosion resistance of the stir zone (SZ) is attributed to the rapid and easier development of a stable passive layer [34], a direct consequence of the microstructural transformations induced by the friction stir welding (FSW) process.…”

A Review on the Corrosion Performance of Magnesium Alloys in Biomedical Applications

“…Nonetheless, these procedures can be expensive and timeconsuming. Coatings, such as anodizing and plasma electrolytic oxidation, can provide excellent corrosion resistance but can be prone to delamination and cracking [38,39]. Hence, the choice of method depends on the specific application and performance requirements.…”

Microstructure and mechanical properties of friction stir welded AZ31 magnesium alloy reinforced with ZrB2

“…Specifically use of ZrB 2 particles as reinforcement has always enhanced the mechanical properties of MMCs [17,18]. To achieve this, a carefully designed set of welding parameters is employed during the FSW process [19,20]. The study encompassed an examination of essential mechanical features, such as ultimate tensile strength, yield strength, hardness, and corrosion tests.…”