Deformation Behavior Of Mg Alloy Research Articles

Effect of grain boundary segregation of rare earth element on deformation behavior of Mg alloys

Effect of grain boundary segregation of rare earth element on deformation behavior of Mg alloys

Effect of rare earth element yttrium on migration behavior of twin boundary in magnesium alloys: a molecular dynamics study

The addition of rare earth (RE) elements can effectively improve the mechanical properties of Mg alloys, which is attributed to its ability to regulate the plastic deformation behavior of Mg alloys. Here, the effects of the concentration of RE element Y and temperature on the migration behavior of twin boundary (TB) in the Mg alloys are investigated by molecular dynamics simulation. The results show that Y element has a softening effect on the migration of TB and promoted TB migration in the Mg alloys. The higher concentration of Y element, the stronger the softening effect on TB migration, and also the faster the migration speed of TB. The results indicate that higher temperature is beneficial to TB migration, and the softening effect of Y element on TB migration in the Mg alloys decreases with the increase of temperature. In addition, the migration mechanism of TB in the Mg alloys is analyzed in detail. This work provides a theoretical basis for the design and preparation of high-performance Mg 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.

Insight into the Role and Mechanism of Nano MgO on the Hot Compressive Deformation Behavior of Mg-Zn-Ca Alloys

Aiming to investigate the role and mechanism of nano MgO on the hot compressive deformation behavior of Mg alloys, the Mg-3Zn-0.2Ca alloy (MZC, in wt%) and the 0.2MgO/Mg-3Zn-0.2Ca alloy (MZCM, in wt%) were investigated systematically in the temperature range of 523–673 K and the strain rate range of 0.001–1 s−1. MZCM shows finer grains and second phase because of the refinement effects of added MgO. Flow behavior analysis shows that the addition of nano MgO promotes the dynamic recrystallization (DRX) of MZC. The flow stress of MZCM is lower than that of MZC during deformation at 523–623 K but exhibits a reverse trend at 673 K and 0.1–1 s−1. The constitutive analysis indicates that dislocation climb is the dominant deformation mechanism for MZC and MZCM. The addition of nano MgO particles decreases the stress sensitivity and deformation resistance for thermal deformation and improves the plasticity of the MZC. Besides, according to the processing map constructed at strains of 0.7 and corresponding microstructure evolution, MZCM exhibits higher power dissipation efficiency and smaller instability regions than MZC, and the optimum hot working condition for MZCM was determined to be at 623–653 K and 0.01–0.001 s−1.

Dynamic mechanical behavior of magnesium alloys: a review

AbstractLight-weight magnesium alloys have great potential to be used in various fields due to their excellent combination of physical and mechanical properties. In crystals, hexagonal metals are distinct from cubic metals because they have a smaller number of slip systems and twinning activity. Sudden impact under a high strain rate causes complex deformation in magnesium alloys and limits their widespread use in defense and industrial applications. Complex deformation is also attributed to the initial processing history of the magnesium alloys. To systematically explain this complex dynamic behavior, this review focuses on the microstructural evolution of Mg alloys that were subjected to high strain rate compression. Moreover, unresolved problems and future targets are discussed in the “conclusion” section to more effectively understand the complex deformation behavior of Mg alloys described in this paper.

Elevated-Temperature Deformation Behavior and Microstructural Evolution of Mg–3Al–1Zn Alloy

Magnesium (Mg) and its alloys are promising materials for many new and advanced applications because of their natural abundance, low density, and good thermomechanical properties. In this study, the elevated-temperature deformation behavior of Mg alloys in addition to their formability and high-temperature application range was assessed between 250 and 400 °C and at different strain rates between 1 × 10−3 and 5 × 10−5 s−1. An elevated-temperature constitutive equation, which addresses and describes the elevated-temperature deformation mechanism, was obtained. Moreover, the related Zener–Hollomon parameter was experimentally established for the selected Mg alloy. The activation energy of the investigated alloy was determined to be 120.7 kJ/mol. According to the results, the activation energy was found to be very similar to the activation energy of self-diffusion for Mg alloys. The evolution of the non-deformed microstructure of the as-received sample within the investigated temperature range was also studied, and the relevant mean linear intercept grain size was estimated. Mechanical property deterioration was investigated, and the relevant microstructures were characterized.

Highly localized shear deformation in a Mg–Al–Mn alloy subjected to ballistic impact

Shear localization, which might result in the formation of shear bands in materials, is considered as a dominating deformation mechanism in materials under dynamic loading. In the present study, the microstructures of twin-induced ASBs in a Mg–Al–Mn alloy under ballistic impact were studied using scanning electron microscope and transmission electron microscope to investigate the localized shear deformation behavior of Mg alloys under high strain rate deformation. The results show that highly localized shear deformation mainly occurs at the boundary regions of deformed twins, resulting in the formation of narrow shear bands. The twin-induced ASBs composed of fine recrystallized grains and Mg17Al12 precipitates, while the internal part of twins shows the microstructure with elongated grains. The initiation of ASBs at the twin boundary regions is mainly attributed to the stress concentration at twin boundaries due to the dislocation pile-up. These results can contribute to further understanding of the shear deformation behavior of Mg alloys under dynamic loading.

Plastic deformation behavior of Mg alloys by underwater shock wave using air pressure

Plastic deformation behavior of Mg alloys by underwater shock wave using air pressure

In-Situ Quantitative TEM Investigation on the Dynamic Evolution of Individual Twin Boundary in Magnesium Under Cyclic Loading

Quantification of dynamics of individual twin boundary (TB) migration such as the velocities and corresponding stresses, is of critical importance for understanding the deformation behavior of Mg alloys. By conducting in-situ cyclic loading experiments on a submicron magnesium pillar inside transmission electron microscope (TEM), the dynamics of an individual TB migration and the associated twinning-detwinning phenomena are systematically investigated. It is found that the TB can migrate forward and backward under each cyclic loading paths, corresponding to the twinning-detwinning cycles. The TB morphology changes constantly during its migration. Surprisingly, the stress required for TB migration is found to be higher in compression than in tension, and the TB migration velocity in compression is slower than in tension. A mechanism associated with prismatic-basal transformation is proposed to interpret such tension-compression asymmetry. The considerable amount of energy absorbed during the TB migration is believed to account for at least part of the good damping properties of Mg. Our results are also expected to benefit the modeling of deformation twinning behavior in Mg and other HCP metals.

The Effect of Nd on the Tension and Compression Deformation Behavior of Extruded Mg-1Mn (wt pct) at Temperatures Between 298 K and 523 K (25 °C and 250 °C)

The tension and compression deformation behavior of extruded magnesium-1 wt pct manganese alloys with nominally 0.3 wt pct (MN10) and 1 wt pct neodymium (MN11) was studied over the temperature range of 298 K to 523 K (25 °C to 250 °C). Nd additions to Mg alloys tend to reduce the strong basal texture exhibited by conventional wrought Mg alloys and this work was intended to study the effect of Nd on the deformation behavior of Mg alloys. Insitu tensile and compressive experiments were performed using a scanning electron microscopy, and electron backscatter diffraction was performed both before and after the deformation. A slip trace analysis technique was used to identify the distribution of the deformation systems as a function of strain, and based on this analysis and the texture of the undeformed samples, the critical resolved shear stress ratios between the deformation systems were estimated. In the case of MN11, the deformation behavior under tension at all temperatures was dominated by slip, while in compression, extension twinning was the major deformation mode. In tension at 323 K (50 °C), extension twinning, basal, prismatic 〈a〉, and pyramidal 〈c + a〉 slip were active in MN11. Much less extension twinning was observed at 423 K (150 °C), while basal slip and prismatic 〈a〉 slip were dominant and presented similar relative activities. At 523 K (250 °C), twinning was not observed, and basal slip controlled the deformation. With the reduction of Nd content, less slip deformation and more twinning were observed during the tensile deformation. However, like for MN11, the extent of twinning in MN10 decreased with increasing temperature and basal slip was the primary deformation mode at elevated temperatures. Extension twinning was the major deformation mode under compression for all test temperatures in MN10 and MN11. The tensile strength decreased with increasing temperature for both alloys, where MN10 was slightly stronger than MN11 at 323 K (50 °C), which was expected to be a result of the stronger basal texture exhibited by MN10 due to its lower Nd content. However, MN11 maintained its strength more at elevated temperatures compared with MN10, and this was explained to be a result of the greater Nd content.

Atomistic modeling of pure Li and Mg–Li system

Interatomic potentials for pure Li and the Mg–Li binary system have been developed based on the second nearest-neighbor modified embedded-atom method formalism. The potentials can describe various fundamental physical properties of pure Li (bulk, point defect, planar defect and thermal properties) and alloy behaviors (thermodynamic, structural and elastic properties) in reasonable agreement with experimental data or higher-level calculations. The applicability of the potential to atomistic investigations on the deformation behavior of Mg alloys and the effect of Li is demonstrated.

Effect of Texture on Deformation Behavior of AZ31 Mg Alloy

Hot rolled Mg alloy has a preferred orientation, which affects the deformation behavior of Mg alloy. In this work, load relaxation and tensile tests after hot rolling process were performed to clarify the effect of the texture on deformation behavior of AZ31 Mg alloy and the results were analyzed based on an internal variable theory proposed by one of the authors. The analysis of the deformation behavior is then correlated to XRD pole figure results of the texture. The analysis result of Mg alloy was found to be comparable to the results obtained from the test of Ti alloys, which has the same HCP structure.

Warm Hemming of Magnesium Sheet

Magnesium sheet has received increasing interest for automotive body and closure applications. However, implementation of these applications faces many challenges involving room temperature formability. Hemming a closure panel with a magnesium outer panel will be difficult because of the sharp bend radius. Bending behavior of AZ31B-O at elevated temperatures was investigated to approximate the hemming of closure panels with acceptable surface appearance. Surface quality from small-radius bending was quantified as a function of temperature between 180 and 300 °C. Flanging with a 1.5 mm die radius yielded an acceptable surface quality at 210 °C and higher. Hemming required a minimum temperature of 270 °C for an acceptable surface condition with a 2 mm outer radius. The complex pattern of grain size and morphology of the deformed microstructure was documented with respect to the elevated temperature deformation behavior of Mg alloys. These results suggest that Mg can be hemmed at elevated temperatures with a small radius (∼1½ times the sheet thickness) and therefore could be used for vehicle closures.