Deformation Of Magnesium Alloy Research Articles

Effect of extrusion temperature on microstructure and mechanical properties of ZTM631 magnesium alloy

Magnesium alloys are widely used in the fields of aviation, electronics, and automotive manufacturing due to their advantages of lightweight and high specific strength. Studying high-performance and low-cost deformed magnesium alloys to adapt to more application scenarios has important value. In the present work, the effect of extrusion temperature on the microstructure and mechanical properties of Mg-6Zn-3Sn-0.9Mn (ZTM631) alloy was investigated. Besides, the ultra-high cycle fatigue (VHCF) performance and fatigue failure mechanism of ZTM631 alloy was explored. Results show that extrusion temperature significantly affect the microstructure of ZTM631 alloys. Firstly, alloys extruded at 300℃ possess a relatively fine grain size, because the lower extrusion temperature prevent the grain growth. Secondly, phases precipitate at 300°C and 350°C with a large size (more than 1 µm) are mainly α-Mn phase. while for the alloys extruded at 400°C, both α-Mn and Mg2Sn phases with the size larger than 1 µm can be found in the matrix. Thirdly, alloys extruded at 400℃ exhibit the best mechanical properties, due to the combination of the grain refinement and precipitation strengthening. Fourthly, during the VHCF failure process, the crack preferentially generates at the densely distributed α-Mn phases for the alloy extruded at 300°C and 350°C, while the crack initiate near the Mg2Sn particles for the alloy extruded at 400°C. Also, undynamic recrystallized (un-DRXed) grains with severe deformation exist in the alloys extruded at 300℃ and 350℃, thus accelerating the crack initiation. This fundamental investigation provides theoretical information for developing high-performance Mg-Zn-Sn alloys with high strength and expanded their application fields.

Effects of Bulk LPSO Phases on Mechanical Properties and Fracture Behavior of As-Extruded Mg-Gd-Y-Zn-Zr Alloys

Despite the consensus on the constructive effect of LPSO (long-period stacking-ordered) phases, the true effect of bulk LPSO phases on strengthening and toughening in deformed magnesium alloys is still controversial. This article, which introduces the alloys Mg-8Gd-4Y-0.6Zn-0.5Zr, without bulk LPSO phases, and Mg-8Gd-4Y-1.6Zn-0.5Zr, containing bulk LPSO phases, details a systematically comparative analysis conducted to clarify the true contribution of bulk LPSO phases to the properties of as-extruded alloys. The results indicate that bulk LPSO phases significantly improve strength by refining grain sizes remarkably. But contrary to expectations, bulk LPSO phases themselves only provide a small strengthening effect and deteriorate plasticity, ascribed to the poor compatible plastic deformation of bulk LPSO phases. More importantly, this work may offer new insights into the strengthening and toughening of LPSO phases for further research and engineering applications of this series of alloys. Additionally, an example of a design strategy for Mg-Gd-Y-Zn alloys with superior strength and excellent plasticity is proposed at the end of this article.

Enhanced deformability of WE43 magnesium alloy by activation of non-basal slip and twinning deformation modes in the equal channel angular pressing at room temperature

Activation of the prismatic and pyramidal slip systems, along with the twinning as the secondary deformation mechanism, assists in the accommodation of a larger plastic strain during the deformation of magnesium alloys. In this paper, deformation mode activity and texture evolution of the WE43 magnesium alloy were investigated during core-sheath equal channel angular pressing (ECAP) at room temperature. Texture studies and transmission electron microscopy inspections suggest that the mechanisms behind the ECAP at room temperature assisted by back pressure were activation of (101¯0) prismatic slip (as the primary mechanism), as well as extension and contraction twinning.

Room temperature static recrystallization phenomenon in a deformed Mg96.6Zn1Y2.2Zr0.2 alloy

Room temperature static recrystallization phenomenon was observed in a deformed magnesium alloy (solid solution Mg96.6Zn1Y2.2Zr0.2 (at.%)), which was compressed at room temperature to a strain of 31.6% and placed naturally for 62 months. By characterizing the microstructure before and after natural placement with transmission electron microscopy, it was determined that the recrystallization mechanism was associated with the activation of a significant number of {101¯2} twins and 〈a〉 or 〈c + a〉 dislocations during the compression process, as well as the hindrance to dislocations of twin boundaries and stacking faults that were enriched with solute elements. These findings not only demonstrate that static recrystallization can occur at low strains and low temperatures over extended periods for some alloys, but also emphasize the importance of monitoring the microstructure and properties of the cold-worked alloys during long-term service without heat treatment.

Texture weakening and ductility improvement of Mg-1.1Mn-0.5Al alloy via medium temperature-high reduction rolling: twinning variants selection and dynamic recrystallization mechanism

The weakening of basal texture is beneficial to improve the formability and mechanical properties of deformed magnesium alloys. In this paper, the microstructure and texture evolution of single pass rolled Mg-1.1Mn-0.5Al alloys with various reduction of 10%–60% at 200 °C were observed to reveal twin variants selection and mediated dynamic recrystallization (DRX) mechanism. The results showed that the type and volume fraction of activated twins were strongly related to rolling reduction. Primary {101¯2} tensile twins (TTWs), which were mainly activated in the 10% reduction rolled alloys, were not sufficient to induce recrystallization due to the absence of cumulative dislocation and lower plastic strain energy. In contrast, {101¯1}/ {101¯3} compression twins (CTWs) and {101¯1}−{101¯2}/ {101¯3}−{101¯2} double twins (DTWs) were preferred for recrystallization because of higher dislocation accumulation and stored strain energy. The occurrence of DRX was beneficial to absorb stored energy, relax stress concentration and weaken basal texture in adjacent domains. Due to the sufficient stress provided by massive basal slip dislocations, the type I and type II DTWs were more commonly observed than the type III and type IV variants, which involved much more dissociations of the mixed <c+a> dislocations in deformed magnesium alloys.

Microstructure and mechanical properties of Mg-Al-Sn-Ca alloy extruded by asymmetric severe shear extrusion with different asymmetric coefficients

Magnesium alloys with grain refinement and texture weakening are long-term targets in the field of light alloys. A new asymmetric severe shear extrusion (ASSE) process is developed in this paper, which is specially designed to refine the grain and weaken the texture of deformed magnesium alloys. The effect of asymmetry coefficient (AC) on microstructure and properties of extruded products was studied. The results show that ASSE can effectively change metal flow. AC-1.5 shows the best mechanical properties, grain refinement (∼8.6 µm) and texture weakening. The yield strength is about 175.9 MPa and elongation is about 19 %. This study provides a theoretical basis for the further development of partial symmetric extrusion.

Microstructure and mechanical properties of GTA-based wire arc additive manufactured AZ91D magnesium alloy

Wire arc additive manufacturing offers advantages in producing large metal structures. The current research on GTA-based wire arc additive manufacturing (GTA-WAAM) of magnesium alloys is focused on deformed magnesium alloys, mainly on the Mg-Al alloy system. However, there is little research on GTA-WAAM for casting magnesium alloy. This study investigates the microstructural characteristics and mechanical properties of AZ91D magnesium alloy (AZ91D-Mg) deposited by GTA-WAAM. Single-pass multilayer thin-walled components were successfully fabricated. The results show that equiaxed grains dominate the microstructure of the deposited samples. During the remelting process, the precipitated phases dissolve into the matrix, and they precipitate and grow from the matrix under the thermal effect of the subsequent thermal cycle. The mechanical properties in the vertical and horizontal directions are similar, showing higher overall mechanical properties than the casting parts. The average yield strength is 110.5 MPa, the ultimate tensile strength is 243.6 MPa, and the elongation is 11.7%. The overall hardness distribution in the deposited sample is relatively uniform, and the average microhardness is 59.6 HV0.2.

Corrosion resistance evaluation of biodegradable magnesium alloy vascular stents optimized by mechanical adapted polymer coating strategy

Surface modification coating of magnesium alloy stents as a physical barrier is to inhibit the corrosive medium from contact with matrix. In view of the complex deformation behavior of stent, mechanical adopted polymer coating strategy was considered in our work. Here, a relatively high plasticity polymer- poly(butyl acrylate) (PBA) was applied as the outer protective layer on the surface of magnesium alloy discs and stents through a dip-coating method and ultrasonic spraying system respectively. Compared with low plasticity poly(d,l-lactide) (PDLLA) control group, mechanical property of PBA polymer film were detected, furthermore, the static corrosion behaviors of PBA/MgF2 flake samples were investigated by electrochemical and immersion tests for a period time. The morphologies and degradation behaviors of stents after grip-expansion were conducted to explore the mechanical adaptability of PBA/MgF2 coating with magnesium alloy stent. PBA/MgF2 composite coating could improve the corrosion resistance of both static and deformed magnesium alloys, exhibiting a long-term protection. Especially, PBA-coated stent maintained the structural integrity and a relatively smooth surface after 21 days of service. Therefore, it is inferred that a coating material with high elongation at break is more mechanical adaptability with stent deformation to reduce the degradation rate of magnesium alloy stents.

Study on High-Strain-Rate Deformation of Magnesium Alloy Using Underwater Shock Waves Generated by High-Voltage Electric Discharge of Thin Wire

Magnesium is an abundant material with high specific strength, and its use as a structural metal is increasing. However, its properties cause difficulty in its formation at room temperature. Therefore, the objective of this study was to form a magnesium alloy at room temperature using an underwater shock wave generated by the discharge of an aluminum wire. Forming was conducted using an auxiliary plate composed of aluminum instead of magnesium alloy alone. In addition, hyperbolic and parabolic pressure vessels were employed. Numerical simulations were performed to measure the pressure values, propagation of underwater shock waves, and deformation of the magnesium alloy. Large deformation was observed when an auxiliary aluminum plate was placed on the upper surface of an AZ31 magnesium alloy plate inside the hyperbolic pressure vessel.

Microstructures and mechanical properties of Mg–5Li–4Sn–2Al–1Zn alloy after hot extrusion

In this work, Mg–5Li–4Sn–2Al–1Zn deformed magnesium alloy was prepared and the effects of the extrusion process on its microstructure, texture evolution, and mechanical properties were investigated. The microstructures of as-homogeneous and as-extruded alloys were characterized by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results show that the alloy underwent dynamic recrystallization (DRX) after hot extrusion processes. Drastic refinement occurred in grain size, and the weakening of the basal fiber texture was obvious after the Forward-Parallel Channel Extrusion process, and the microstructure was more uniform. As a result, the mechanical properties of the alloy were superior after the Forward-Parallel Channel Extrusion process, and the best combination of strength and plasticity was obtained after the 105° FPE process. YS, UTS, and EL were 187 MPa, 275 MPa, and 15%, respectively. The increase in strength is mainly attributed to grain boundary strengthening and the pinning effect of shattered particles on the migration of dislocations and grain boundaries. The increase in plasticity can be explained by the activation of non-basal slip and the weakening of the basal fiber texture, the fine grains can coordinate the plastic deformation well and improve the plasticity of the alloy to some extent.

Analysis of the Microstructure Role in the Yield Asymmetry of Extruded Mg-LPSO Alloys Using In Situ Diffraction Experiments

The effect of microstructure and processing parameters on the mechanical behavior of extruded Mg-Y2x-Znx alloys containing different volume fractions of the long-period stacking order (LPSO) phase is evaluated using in situ diffraction experiments. The Mg-LPSO extruded alloys exhibit a microstructure consisting of a mixture of fine dynamically recrystallized α-Mg grains, highly oriented non-recrystallized coarse α-Mg grains with the basal plane parallel to the extrusion direction, and particles of the LPSO phase elongated in the extrusion direction. The volume fraction of dynamically recrystallized α-Mg grain areas tends to increase as the volume fraction of the LPSO phase and the processing stress increase. In situ diffraction experiments have allowed the understanding of the elastic–plastic behavior of non-DRXed and DRXed grains, and their individual contribution to the macroscopic deformation of magnesium alloys containing LPSO phases and, consequently, the reverse tension–compression asymmetry.

Study on the compressive deformation behavior of a basal textured AZ31 magnesium alloy from the perspective of local strain

For basal textured magnesium alloy subjecting to in-plane compression, the deformation is complicated since twinning, dislocation slipping and their intersecting are involved. In this work, a high-resolution digital image correlation (HR-DIC) technique combined with electron backscatter diffraction (EBSD) was used to quantitatively study the deformation behavior of AZ31 alloy in in-plane compression. Grain-scale local strain characteristics were emphasized. It is found that the local strain in the twined region is homogeneous and will not continuously increase with the applied nominal compression strain if no dislocation slipping is activated. When twinning is accompanied by dislocation slipping in the deformation of magnesium alloys, which is actually the common case, the strain contribution by the twinning can be calculated by transferring its shear from the twin frame to the sample frame. The results of this work can be beneficial for further understanding of deformation mechanism of magnesium alloy and the development of physics-based simulation models.

Comparison of Corrosion Performance of Extruded and Forged WE43 Mg Alloy.

Adjusting the microstructure through the deformation process is one of the ways to improve the properties of Mg alloys. Most studies have focused on the influence of the microstructure after deformation treatment on the mechanical properties of Mg alloys. In this paper, extruded and forged Mg-Gd-Y-Nd-Zr alloys were selected to investigate the corrosion performance of two deformed magnesium alloys immersed in 0.6 M NaCl solution using a hydrogen evolution test, a weight loss test, an immersion experiment, and an electrochemical test. The results showed that WE43 alloys undergoing different deformation treatments presented different microstructures, which led to different corrosion behaviors and corrosion resistance. The extruded WE43 alloy showed uniform corrosion, while the forged WE43 alloy suffered severe local galvanic corrosion. Meanwhile, the corrosion rate of the forged WE43 alloy was about four times faster than that of the extruded WE43 alloy.

The role of grain boundary plane in slip transfer during deformation of magnesium alloys

Slip transfer across grain boundaries (GBs) is an important mechanism for HCP metals to accommodate intergranular deformation incompatibility. In this work, an in-situ SEM/EBSD study was conducted to study basal-slip-induced non-basal <a> slip behavior in a Mg–Y alloy. The indices of dislocation slip systems of slip traces at sample surface were determined by a lattice rotation analysis method based on EBSD images. It was shown that the disorientation angles of GBs have a strong influence on the slip transfer behavior. The experimentally determined preferential disorientation angle ranges for basal-slip-induced pyramidal I <a> slip and prismatic <a> slip events have been correlated to the geometrical compatibility between the source and triggered slip systems, in terms of m' criterion. However, a statistic showed that some slip transfer events do not obey the m' criterion. Instead, they are rather sensitive to the GB plane orientations. To reveal the roles played by the GB plane, sectional polishing and EBSD characterization to determine the orientation of GB plane have been conducted. It is revealed that, in addition to the GB disorientation angle, the activation of slip transfer in Mg is essentially dependent on the plane orientation of local GBs. It also demonstrated that the M criterion, based on the match of intersection lines between dislocation slip planes to GB planes and slip directions, was more rational to predict the activated slip systems by the m' criterion. This work emphasizes the importance of GB plane orientation when attempting to understand the slip transfer mechanism in deformed magnesium alloys.

Superplastic deformation behavior of Mg alloys: A-review

The magnesium alloys are the next-generation lightweight metal materials; however, the production of the complex shape components of thermo-mechanical processed magnesium alloys is very limited in comparison to their die-casted counterparts. Both high strain rate and low-temperature processing are required to save time and cost for the project. Uniaxial tensile testing has been vastly used for determining the plasticity of magnesium alloys at elevated temperatures. Therefore, this review article sheds light on superplastic behaviors under the uniaxial tensile loading of different magnesium alloys. This review also emphasizes low and high-temperature superplasticity, high strain rate superplasticity, deformation mechanism, thermal stability, texture evaluation, and fracture mechanism of extruded/rolled and severe plastic deformed magnesium alloys. At the end of the review, some technical issues have been addressed which can be beneficial for further enhancement in the superplasticity of magnesium alloys.

Growth Mechanism of Ceramic Coating on ZK60 Magnesium Alloy Based on Two‐Step Current‐Decreasing Mode of Micro‐Arc Oxidation

The ZK60 deformed magnesium alloy is treated by micro‐arc oxidation (MAO) and processed in the optimized silicate–phosphate electrolyte system, which is controlled under the two‐step current‐decreasing mode. The mechanism of discharge in the MAO process is investigated using the voltage–time curve and morphology of the spark discharge at different durations. The microstructures of the coatings fabricated at different durations are investigated. The rules of the coating ingrowth and/or outgrowth, the formation mechanisms of micropores, and microcracks in the coatings are explored systematically. The corrosion resistance of the coatings is measured by electrochemical methods. Through the exploration of the mechanism, two types of micropores in the coating are summarized: the in situ discharge growth type and the pores‐sealed type, and also three types of microcracks. The results illustrate the changes of the elements on the surface of the coating and Mg, O, and Si are incorporated into the coating formation process. The specimens show the best corrosion resistance after the two‐step current‐decreasing mode treatment.

Molecular Dynamics Study on Uniaxial Compression Transformation of Magnesium Alloy

As a new method of calculating materials, molecular dynamics simulation can effectively reproduce the mechanical behavior of materials at the atomic level. In this paper, through the construction of the AZ31 magnesium alloy model, the uniaxial compression deformation of magnesium alloy at different temperatures and strain rate is simulated by molecular dynamics method, the mechanical properties and microstructure changes of magnesium alloy are analyzed, the phase transformation mechanism of magnesium alloy under uniaxial compression is revealed, and the effects of temperature and strain rate on the phase transformation of magnesium alloy are explored at the nanometer scale. It provides a theoretical basis and necessary basic knowledge for the design and development of Mg-based nanostructured alloys with excellent mechanical properties.

Mechanisms of elastic–plastic deformation in magnesium alloy studied using neutron diffraction and crystallite group method

Mechanisms of elastic–plastic deformation in magnesium alloy studied using neutron diffraction and crystallite group method

Nature of High-Temperature Strength of Deformed Magnesium Alloy of the Mg – Zn – Zr – REE System

Nature of High-Temperature Strength of Deformed Magnesium Alloy of the Mg – Zn – Zr – REE System

A comparative study of plastic deformation mechanisms in room-temperature and cryogenically deformed magnesium alloy AZ31

Abstract In this work, a commercial cast magnesium alloy AZ31 was compressed at room and cryogenic temperatures (RT and CT) to study how the twins and dislocations affect the flow stress, plastic strain and strain hardening. Cryogenic deformation suppresses the dislocation activities to enable the effects of dislocation slip and twinning on plasticity to be separately interrogated. A quasi-in-situ Electron Backscatter Diffraction (EBSD) method was used to trace the evolution and distribution of twins and geometrically necessary dislocation (GND) density manifested as kernel average misorientation (KAM) in the same group of grains before and after plastic deformation, at RT and CT respectively. Compared to the RT deformation, higher flow stress, higher strain hardening rate and moderately reduced strain to failure were observed in the CT deformation. These interesting findings were rationalised by the subsequent EBSD analysis. It is found that the increased fraction of finer twins and twin-twin interactions rather than dislocation density leads to higher stress and higher strain hardening at CT. This suggests that the hardening effect induced by twin boundary and twin-twin interactions is considerably more effective than dislocation density hardening.