Magnesium Alloy Research Articles

Assessing hidden corrosion in AZ91 magnesium alloy via infrared thermography in simulated atmospheric acid rain conditions

Abstract Magnesium alloys have garnered significant attention in the aerospace and marine industries due to their exceptional mechanical properties, including low density and a high strength-to-weight ratio. Despite these advantages, their widespread adoption is hindered by susceptibility to corrosion, particularly under harsh environmental conditions. While considerable research has focused on uniform surface corrosion of magnesium alloys, studies addressing hidden corrosion remain limited. Hidden corrosion is a critical defect that can severely compromise the structural integrity of aging aircraft. In this study, the hidden corrosion behavior of the AZ91 magnesium alloy was explored using infrared thermographic non-destructive testing. Seven blind holes were drilled into the surface of the alloy, which was then exposed to simulated acid rain for ten days to examine the effects of corrosion. The rate of corrosion in the drilled samples was observed to be slightly higher compared to bare samples, likely due to the accumulation of acid in the crevices. Changes in the initial and final hole dimensions and volume were used to determine the corrosion rate, providing valuable insights into the mechanisms governing hidden corrosion in magnesium alloys. This work offers a deeper understanding of hidden corrosion, with potential implications for improving the longevity and safety of critical aerospace and marine components.

Synergetic effect of in-situ TiB2 reinforcement and nano precipitation on wear behavior of ZE41 magnesium matrix composite

The rise in carbon dioxide pollution and energy consumption has increased the demand for lightweight materials such as magnesium in automotive and aerospace industries. However, magnesium alloys face challenges like poor wear resistance and mechanical strength. To overcome these limitations, a promising approach involves developing heterogeneous hybrid microstructures through reinforcement addition and microstructural engineering. This study focuses on the tribological performance of a newly developed in-situ sub-micron sized TiB2/ZE41 composite under various microstructural conditions, comparing it to the unreinforced ZE41 Mg alloy. Wear experiments were conducted using a pin-on-disc tribometer under normal loads of 10, 20, 40, and 60 N at a sliding velocity of 1 m/s. Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) was used to analyze the worn surfaces in order to identify damage types and surface distortions. By correlating worn surface microstructures with test parameters, predominant wear mechanisms for each material condition under specific loads were determined. Results consistently showed that the presence of in-situ TiB2 reinforcements, β-phase, and rare-earth precipitates enhanced wear resistance regardless of the load conditions. Additionally, the study established a scientific understanding of the wear behavior of ZE41 Mg alloy, with and without in-situ TiB2 particles and precipitates, through analysis of dominant wear mechanisms, wear-induced subsurface deformation mechanisms, kernel average misorientation, grain orientation spread, and microhardness evaluation.

Exploring the Corrosion Performance of AZ31 Magnesium Alloy under Acidic and Alkaline Conditions

Exploring the Corrosion Performance of AZ31 Magnesium Alloy under Acidic and Alkaline Conditions

A strategy for introducing biopotency-enhanced chirality coating on bio-magnesium

Biomedical magnesium alloys (Mg) are often considered potential metallic materials for bone repair scaffolds due to their excellent biomechanical properties, biocompatibility, and biodegradability. However, their rapid degradation behavior is insufficient to support the rapid growth and repair of living tissues. The new surface modification methods to slow down the degradation rate of Mg scaffolds and promote the rapid growth of living tissues is urgent. Here, we developed a chiral-enhanced composite functional coating on the surface of biomedical magnesium. Specifically, a chiral supramolecular hydrogel with graphene oxide (GO) was used to simulate the chiral environment of biological systems, enhancing the adsorption of osteogenic growth factors. Additionally, the silane layers cleverly crosslink traditional silane chains with supramolecular chiral fibers through a hydrogen bond network, which allows the bonding strength (critical loads) of the composite coating to be maintained between 245–275 mN and retains structural integrity when soaked in SBF for 7 days. It was found that both MC3T3-E1 cells growth and BMP-2 adhesion were significantly enhanced by GO-added left-handed chiral coatings, which exhibit superior bone growth-promoting effects. In summary, incorporating chiral features into functional coatings represents a transformative approach in the design and application of bone defect repair materials.

Effect of Loading Direction on Tensile-Compressive Mechanical Behaviors of Mg-5Zn-2Gd-0.2Zr Alloy with Heterogeneous Grains

The tension-compression yield asymmetry caused by the strengthening of Mg-Zn-Gd-Zr alloy due to extrusion deformation is an important issue that must be addressed in its application. In this study, the effects of loading direction on the tensile and compressive mechanical behaviors of Mg-5Zn-2Gd-0.2Zr alloy were systematically investigated. As the loading angle (the angle between the loading direction and the extrusion direction) increases from 0° to 30°, 45°, 60° and 90°, the tensile yield strength decreases more significantly than the compressive yield strength. Consequently, the tension-compression yield asymmetry is gradually improved. Additionally, the ultimate compressive strength decreases more markedly than the ultimate tensile strength with the increment of the loading angle. In tensile tests conducted at 0°, 30° and 45°, two distinct stages of decreasing strain hardening rates are typically observed. For the 60° and 90° tensile tests, one unusual ascending stage of strain hardening rate is observed. For all compressive tests, three stages of strain hardening are consistently noted; however, the increment in strain hardening rate caused by {10–12} extension twinning decreases with the increasing loading angle. A model combining loading angle and Schmid factor distribution was established. The calculated results indicate that the dominant deformation modes during the yielding process also vary significantly with the loading conditions. This clarification highlights the differences in yield strength variations between tension and compression. Finally, an analysis of the plane trace and crack propagation direction near the fracture surface reveals the fracture mechanisms associated with tensile and compressive tests at different loading directions. This study promotes understanding of the mechanical behaviors of Mg-5Zn-2Gd-0.2Zr alloy under different loading directions, and helps to thoroughly elucidate the anisotropic effects of texture on the mechanical properties of magnesium alloys.

Study on the investigation of creep behaviour in squeeze cast Ca-modified AZ91 magnesium alloy

ABSTRACT The AZ91 (Mg-Al) alloy is the most commonly used Mg-cast alloy with high specific strength and excellent die-castability; however, its poor creep performance limits its applications at elevated temperatures. In the present investigation, the effect of Ca addition on the microstructure development and creep performance of squeeze-cast AZ91 alloy recognised as AZX911 alloy has been investigated at 150°C–250°C temperature under 65 and 80 MPa stress. The addition of Ca in the AZ91 alloy results in the precipitation of the thermally stable Al2Ca intermetallic phase, which partially suppresses the precipitation of the thermally unstable β-Mg17Al12 phase and significantly improves the creep resistance of the AZ91 Mg alloy. The governing creep mechanism of AZX911 alloy is found to follow power law creep with n = 3.49 at 150°C that mainly results from dislocation climb. In contrast, a transition to power-law breakdown is observed at 175°C. The resistance to creep deformation of AZX911 further improves with heat treatment at 450°C as compared to the as-cast specimen of the same alloy due to the complete dissolution of the β-Mg17Al12 phase. The activation energy of phase dissolution, estimated using the Kissinger method, is found to be higher (923 kJ/mol) for the Al2Ca intermetallic phase as compared to that for β-Mg17Al12 phase (664 kJ/mol) in AZX911 alloy.

Outside-in directional sodium deposition through self-supporting gradient fluorinated magnesium alloy framework toward high-rate anode-free Na batteries

Constructing high-rate sodium anodes promotes the progress of high energy/power density Na metal batteries. However, it lacks effective strategies to regulate Na deposition behaviors under high current density and high capacity, greatly compromising their energy density, cycling life, and safety. Herein, we construct a self-supporting framework host consisting of nitrogen-doped carbon hollow nanofibers with uniformly embedded MgF2 (MgF2@NCHNFs), facilitating outside-in directional Na deposition. During the first Na plating, the MgF2 in the tube wall of NCHNFs is in-situ converted to gradient fluorinated alloy architecture, where the outmost NaF homogenizes Na+ flux, the subsurface sodiophilic N sites and gradient distribution Mg sites facilitate Na deposition into the internal space of hollow nanofibers. Thus, the MgF2@NCHNFs exhibit dendrite-free and directional Na deposition behaviors even at high rate (10 mA cm-2) and high capacity (10 mAh cm-2). The superiorities of the Na-MgF2@NCHNFs are demonstrated in high-rate anode-less/anode-free sodium metal batteries using sodium vanadium phosphate and sulfur as cathodes. Furthermore, the pouch cells deliver a superhigh capacity retention of 96.0 % over 400 cycles at 2 C. This work provides a new strategy for practical applications of multifunctional Na hosts in sodium metal batteries, and can extend to other metal batteries.

Corrosion inhibition effect of sodium silicate/triethanolamine complex inhibitor on AZ91D magnesium alloy in 50% ethylene glycol coolant

Corrosion inhibition effect of sodium silicate/triethanolamine complex inhibitor on AZ91D magnesium alloy in 50% ethylene glycol coolant

Microstructural Evolution and Mechanical Properties of Extruded AZ80 Magnesium Alloy during Room Temperature Multidirectional Forging Based on Twin Deformation Mode.

This study investigates the preparation of ultrahigh-strength AZ80 magnesium alloy bulks using room temperature multidirectional forging (MDF) at different strain rates. The focus is on elucidating the effects of multidirectional loading and strain rates on grain refinement and the subsequent impact on the mechanical properties of the AZ80 alloy. Unlike hot deformation, the alloy subjected to room temperature MDF exhibits a lamellar twinned structure with multi-scale interactions. The key to achieving effective room temperature MDF of the alloy lies in combining multidirectional loading with small forging strains per pass (6%). This approach not only maximizes the activation of twinning to accommodate deformation but ensures sufficient grain refinement. Microstructural analysis reveals that the evolution of the grain structure in the alloy during deformation results from the competition between {101¯2} twinning or twinning variant interactions and detwinning. Increasing the forging rate effectively activates more twin variants, and additional deformation passes significantly enhance twin interaction levels and dislocation density. Furthermore, at a higher strain rate, more pronounced dislocation accumulation facilitates the transformation of twin structures into high-angle grain boundaries, promoting texture dispersion and suppressing detwinning. The primary strengthening mechanisms in room temperature MDF samples are grain refinement and dislocation strengthening. While increased dislocation density raises yield strength, it reduces post-yield work hardening capacity. After two passes of MDF at a higher strain rate, the alloy achieves an optimal balance of strength and ductility, with a tensile strength of 462 MPa and an elongation of 5.1%, significantly outperforming hot-deformed magnesium alloys.

Thin-walled and large-sized magnesium alloy die castings for passenger car cockpit: Application, materials, and manufacture

Thin-walled and large-sized magnesium alloy die castings for passenger car cockpit: Application, materials, and manufacture

Investigating formability of AZ31B magnesium alloy sheet with different texture and thickness in combination of the Erichsen experiment and CPFEM model

In this study, the formability of the AZ31B magnesium alloy sheets was investigated in combination of experiment and CPFEM modelling. The deformation mechanisms during the Erichsen forming were revealed and the effect of the related parameters were discussed. It was shown that the simulation results based on the normalized Cockcroft-Latham criterion are consistent with the experimental results. The maximum stress and strain concentrate at the center of dome, and exhibit an elliptical distribution shape. The difference of asymmetry situation between the sheets results from the different textures. The basal <a> slip is the dominant mode, and the prismatic <a> slip is also active to accommodate plastic strain in sheet plane. The relative activity of the pyramidal <c+a> slip is low, but very effective to accommodate the plastic strain in thickness direction. The sheet with higher relative activity of the prismatic <a> and pyramidal <c+a> slips exhibit higher formability. The sheet thickness influences the formability through changing the stress-strain response, as well as the orientation-relationship between stress state and grains which can affect the deformation mechanisms. The formability depends on the plastic strain accommodation ability that is comprehensively related to the averaged plasticity, orientation-relationship between stress state and grains, r-value and n-value. CPFEM modeling is convenient pathway to predict the formability.

Corrosion resistance and biocompatibility of magnesium alloy with bioactive glass-reinforced hydrogel composite coatings

Magnesium (Mg) alloy is a promising candidate for biodegradable implants; however, its rapid degradation can create an unstable physiological environment that hampers tissue regeneration. To address this challenge, a polyvinyl alcohol (PVA) hydrogel composite reinforced with bioactive glass (BG) particles was developed as a coating for Mg alloy pellets, which underwent laser surface texturing (LST) and salting-out processes. results demonstrate that these treatments significantly enhance both the adhesiveness and swelling of the hydrogel coating. Notably, electrochemical corrosion assessments reveal a marked improvement in corrosion resistance, with the Mg–B1-L-S specimen exhibiting the highest performance after salting-out treatment. Electrochemical corrosion assessments revealed a significant enhancement in corrosion resistance for Mg alloy with the hydrogel coating, with the Mg–B1-L-S specimen showing superior performance following salting-out treatment. Immersion tests in simulated body fluid (SBF) confirmed the protective effect of the coatings, indicating that the addition of BG particles and salting-out treatment reduced mass loss and maintained pH stability. Biocompatibility evaluations through in vitro viability tests and osteogenic differentiation assays indicate that the Mg–B1-L and Mg–B1-L-S specimens exhibit superior cell activity, surface adhesion, and osteogenic potential. These findings highlight the effectiveness of PVA-BG hydrogel composite coatings in enhancing the corrosion resistance and biocompatibility of Mg alloy implants, positioning this approach as a significant advancement in the development of biodegradable materials for biomedical applications.

Study on the coating-formation process of micro arc oxidation coating on AZ31B magnesium alloy with Sc(NO3)3 addition

To investigate the effect of the addition of Sc(NO3)3 on the coating-formation process of AZ31B magnesium alloy MAO coating, microarc oxidation was conducted in a silicate-phosphate electrolyte containing 0.5 g/L Sc(NO3)3 for 15 s, 30 s, 60 s, 120 s, 240 s, and 1800 s. The oxidation voltage, surface morphology, and phase composition of the coatings were characterized using SEM, XRD, and XPS. The results indicated that Sc(NO3)3 hydrolytic complexation forms Sc(OH)2+ which leads to more uniform discharge micropores on the MAO coating surface, increasing the oxidation voltage. Compared to the MAO sample without Sc(NO3)3, the coating surface becomes denser and smoother. The MAO coating phase composition is MgO and Mg2SiO4, with Sc present as Sc2O3 in the coating.

Heterogeneous lamella mixed grain structures of strength-ductility synergy in medium strain rate rolled AZ31 magnesium sheets

The increase in strength of Mg and its alloys, like other metals, usually couples with a large reduction in ductility, which limits its widely application. A novelty heterogeneous lamella mixed grain structures could effectively achieve high strength-ductility synergy and are obtained by medium-strain rate rolling with high reduction in single-pass which is an industrial process that can be easily scaled up for large-scale production at low cost, i.e. tensile strength of ∼279 MPa and elongation of ∼21.2 % in low alloying magnesium alloy (AZ31). This novelty heterogeneous lamella mixed grain structure displays fine grain lamella and mixed grain lamella alternative distribution, and twins exist inside mixed grain lamella. During deformation, the twinning occurs in the mixed grain lamella and the heterogeneous lamella mixed grain structures have high Schmid factor (SF) for non-basal slip, resulting in the excellent plasticity. The strength is mainly provided by the fine grain lamella and the twins inside mixed grain lamella. The back stress induced by the heterogeneous structure could dynamically achieve strength and ductility. This work provides a new sight to design the heterogeneous lamella mixed grain structure to obtain different combination of strength and plasticity by adjusting grain size distribution, twin density in mixed grain lamella, aspect ratio of coarse grain and misorientation among coarse grain, fine grain and twin.

Kinetics of Aging and Changes in the Mechanical Properties of Mg – Y – Nd – Gd – Zn – Zr Cast Magnesium Alloy During Overburning

Kinetics of Aging and Changes in the Mechanical Properties of Mg – Y – Nd – Gd – Zn – Zr Cast Magnesium Alloy During Overburning

High-throughput screening of the potential alloying elements for high-strength Mg alloys based on solid-solution strengthening

Abstract 49 types of alloy atomic dopants and their effects on the doping stability and micro-mechanical behaviour of magnesium matrix were investigated using density functional theory and high throughput first-principles calculations. Geometry optimization was performed for each doping system, and the ability of atom doping into the magnesium matrix was assessed based on the doping energy and atomic radius. Results show that the transition metal elements have negative or near negative doping energy, especially for the elements with a radius that similar to Mg. The micro-mechanical properties of the doping system were evaluated by computing the fracture energy and theoretical tensile stress. Through a screening on the doping stability and strengthening effect of 49 types of alloy atoms, a set of elements (Re, Os, Ir, Tc and W, etc.) are screened out that could strengthen the magnesium matrix with a good doping stability. The high throughput screen results serve as a theoretical guide for the selection of appropriate alloy elements for designing the high-strength magnesium alloys in the regime of solid solution strengthening effects.

SLM Magnesium Alloy Micro-Arc Oxidation Coating

In this study, we utilized Selective Laser Melting (SLM) technology to fabricate a magnesium alloy, and subsequently subject it to micro-arc oxidation treatment. We analyzed and compared the microstructure, elemental distribution, wetting angle, and corrosion resistance of the SLM magnesium alloy both before and after the micro-arc oxidation process. The findings indicate that the SLM magnesium alloy exhibits surface porosity defects ranging from 2% to 3.2%, which significantly influence the morphology and functionality of the resulting film layer formed during the micro-arc oxidation process. These defects manifest as pores on the surface, leading to an uneven distribution of micropores with varying sizes across the layer. The surface roughness of the 3D-printed magnesium alloy exhibits a high roughness value of 180 nanometers. The phosphorus (P) content is lower within the film layer compared to the surface, suggesting that the Mg3(PO4)2 phase predominantly resides on the surface, whereas the interior is primarily composed of MgO. The micro-arc oxidation process enhances the hydrophilicity and corrosion resistance of the SLM magnesium alloy, thereby potentially endowing it with bioactivity. Additionally, the increased surface roughness post-treatment promotes cell proliferation. However, certain inherent defects present in the SLM magnesium alloy samples negatively impact the improvement of their corrosion resistance.

Corrosion behaviour of the magnesium-cerium binary alloy designed for degradable medical implants

ABSTRACT Magnesium (Mg) alloys containing rare earths (RE) gained special attention as promising candidates for degradable implant applications. Cerium (Ce) is one of the RE elements which can be tolerated by the human physiological system when used as an alloying element in Mg alloys. In this current research work, Mg-Ce binary alloys (0%, 0.5%, 1%, 1.5%, and 2% Ce by weight) were prepared by the stir-casting method. The developed alloys were characterised, and corrosion performance was assessed by immersion experiments in normal saline solution and by electrochemical experiments. The degradation rate of the developed alloys was measured as decreased with the increased Ce content up to 1.5%. From the polarisation studies, lower corrosion current density values 3.5 × 10−5 A/cm2 and 4.1 × 10−5 A/cm2 were observed for Mg-1.5%Ce and Mg-2%Ce alloys, respectively compared with the other samples. The surface morphologies after removing the corrosion products revealed more degraded regions for Mg and alloys with lower Ce content (0.5% and 1%) compared with 1.5% and 2% Ce. From the results, it is concluded that developing an Mg-Ce alloy with an optimum fraction of Ce (1.5%) is promising to produce degradable Mg-based medical implants with controlled degradation.

Modification of the constitutive model and fracture model of magnesium alloys based on Lode parameter

Modification of the constitutive model and fracture model of magnesium alloys based on Lode parameter

Design of flat hole-clinching for joining polymer and metal sheets

There is a growing need for joining processes capable of joining dissimilar materials, specifically lightweight materials. In this study, flat hole-clinching (FHC) is developed for joining polycarbonate and AZ31 magnesium alloy sheets. A ductile fracture criterion is calibrated using tensile tests and employed in the finite element analysis of the process to investigate the effect of geometric parameters on the joint characteristics and strength. A tool concept is also proposed for the FHC process. Results show that the FHC process enables to successfully connect these sheets without fracture. The flat hole-clinched joint resisted the maximum force of 0.9 kN in the pull-out test, and failed with bottom separation mode.