Discharge properties and electrochemical behaviors of AZ80-La-Gd magnesium anode for Mg-air battery

In this work,the discharge properties and electrochemical behaviors of as-cast AZ80-La-Gd anode for Mg-air battery have been investigated and compared with the AZ80 anode.The microstructure evolution,electrochemical behaviors and surface morphologies after discharge have been discussed to connect the discharge properties.The results indicate that the modified AZ80-La-Gd is an outstanding candidate for anode for Mg-air batter,which has high cell voltage,stable discharge curves,good specific capacity and energy,and good anodic efficiency.It exhibits the best anodic efficiency,specific capacity and energy of 76.45%,1703.6 mAh·g^(-1)and 2186.3 mWh·g^(-1),respectively,which are20.24%,18.92%and 25.71%higher than values for AZ80 anode.Such excellent discharge performance is attributed to the Al-RE particles.They refine the Mg_(17)Al_(12)phase and therefore improve the self-corrosion resistance and desorption ability of AZ80 anode.

Macro-physical field of large diameter magnesium alloy billet electromagnetic direct-chill casting:A comparative study

A comprehensive two-dimensional axisymmetric mathematical model that couples transient electromagnetic force with fluid flow,heat transfer,and solidification was established to describe the interaction of multiphysics field during DC casting.The melt flow,heat transfer,and solidification characteristics under differential phase pulse magnetic field and differential phase low-frequency electromagnetic field(DP-PMF and DP-LFEF)were numerically investigated by means of numerical simulation during electromagnetic direct-chill(DC)casting of AZ31 alloy at the same casting conditions.The effects of differential phase electromagnetic fields on Lorentz forces distributions,melt flow,heat transfer,and liquid sump shape were discussed systematically.Based on measured current waveform,the results were compared with those obtained without magnetic field(MF)and under conventional pulse magnetic field(PMF)and low-frequency electromagnetic field(LFEF)under the same conditions.The results show that the application of magnetic fields can significantly change the solidification process of DC casting.Differential phase magnetic fields(DP-LFEF and DP-PMF)can effectively reduce the temperature of the melt in the liquid sump,and the shallower liquid sump depth can be obtained under the differential phase magnetic fields.A large velocity vibration amplitude and a lower temperature are available simultaneously under DP-PMF,resulting in more uniform temperature distribution.

Crimp feasibility of AZ31 magnesium alloy wide plate at warm temperatures responding to asymmetry

The crimp feasibility of AZ31 Mg alloy wide plate responding to asymmetry and anisotropy at different temperatures was conducted by bending experiments and numerical simulation.Through the microstructural characteristic,mechanical properties,EBSD and FEM analysis,the results indicated that{10-12}twins and pyramidal(a)slip were dominated at the inner surface layer of the plate,while prismatic and pyramidal(a)slips were controlled at the outer layer when bending at 100℃,and their quantity decreased as the temperature elevation and vanished at 200℃.The flexural deflection increased gradually with the augment of flexural temperature,while the fracture stress weakened.A large number of twins nucleated and grew in the coarse grain,causing major distribution proportion of high angular grain boundaries(HAGBs)at the compression part,which could improve its flexural properties and affect subsequent strain contours,twins and recrystallization distribution.The offset of the neutral layer declined from 1.4125 mm to 0.7261 mm with the temperature rising from 100℃to 250℃when bending,while it was concentrated on 0.0338-0.0481 mm when coiling,accounting for 0.26%-0.37%of the plate thickness.At last,the reel diameter descended with increasing the temperature and coiling rate.

Effects of external field treatment on the electrochemical behaviors and discharge performance of AZ80 anodes for Mg-air batteries

In this work,the effects of external field treatment on electrochemical behaviors and discharge performance of as-cast Mg-8%Al-0.5%Zn(wt%)anodes for Mg-air batteries are systematically investigated in3.5 wt%Na Cl solution.The external field treatment particularly the variable-frequency ultrasonic field can dramatically refine theα-Mg grains andμphases.The grain size decreases from 1594.8±43μm(untreated billet)to 140.6±15μm after variable-frequency ultrasonic field treatment.The values of open circuit potential,electrochemical activity and corrosion resistance of Mg-8%Al-0.5%Zn anode are improved with external field treatment,which should be attributed to refined grains and dispersiveαphase.The external field treatment especially the variable-frequency ultrasonic field improves stability and the value of cell voltage,and enhances the discharge performance of the Mg-8%Al-0.5%Zn anode.The variable-frequency ultrasonic field treated anode has the best discharge capacity and anodic efficiency at current density of 45 m A cm-2,with the values of 1417 m A h g-1 and 63.3%,respectively.The ultrasonic field vibration changes the dissolution behavior ofα-Mg matrix during the discharge process,showing the oriented surface morphologies.

Bauschinger-Like Effect of AZ31 Magnesium Alloy Wide Sheet During the Straightening Process

The Bauschinger-like effect, which showed up in the straightening process of the AZ31 magnesium alloy wide sheet, was investigated through the multi-pass discrete three-point bending–unloading–bending(BUB) experiments. The stress variable, anisotropy, and asymmetry of tension and compression on the straightening process were corresponding to the Bauschingerlike effect. The Bauschinger-like effect in the initial, intermediate, and end of the straightening process was dominated by the twinning, detwinning, and dislocation induced by pyramidal < c + a > slip, respectively. Also, they were responsible for the transformation of the Bauschinger stress parameter(BSP) and Bauschinger energy parameter(BEP). Later, the anisotropic nonlinear kinematic hardening model(ANK model) to describe the Bauschinger-like effect was optimized and simplified.

Hot deformation behavior and processing map of Mg-2Zn-1Al-0.2RE alloy

In this study,uniaxial hot compression tests were carried out between 200 and 400℃ over strain rates of0.001-1 s-1 to investigate the hot deformation behavior of Mg-2 Zn-1 Al-0.2 RE alloy with coarse grains.The average activation energy was measured to be 174.51 kJ/mol.In addition,a constitutive relation based on the Arrhenius equation was established.Dynamic recrystallization(DRX) kinetics were studied by Avrami equation to characterize the evolution of DRX volume fraction.DRX was favored at high temperatures of 300-400℃ and low strain rates of 0.001-0.01 s-1.According to dynamic material model and Prasad’s instability criterion,a maximum power dissipation of 38% and 32% occurs at 400℃/0.001 s-1 and 400℃/0.01 s-1,respectively.According to the proce ssing map,330-400℃/0.001-0.01 s-1was determined as the optimum deformation parameter range.