Effect of Mn content on microstructure and properties of AlCrCuFeMnx high-entropy alloy

AlCrCuFeMnx(x=0,0.5,1,1.5,and 2)high-entropy alloys were prepared using the vacuum arc melting technology.The microstructure and mechanical properties of AlCrCuFeMnxwere analyzed and tested by XRD,SEM,TEM,nanoindentation,and electronic universal testing.The results indicate that the AlCrCuFeMnxhigh-entropy alloy exhibits a dendritic structure,consisting of dendrites with a BCC structure,interdendrite regions with an FCC structure,and precipitates with an ordered BCC structure that form within the dendrite.Manganese(Mn)has a strong affinity for dendritic,interdendritic,and precipitate structures,allowing it to easily enter these areas.With an increase in Mn content,the size of the precipitated nanoparticles in the dendritic region initially increases and then decreases.Similarly,the area fraction initially decreases and then increases.Additionally,the alloy’s strength and wear resistance decrease,while its plasticity increases.The Al Cr Cu Fe Mn1.5alloy boasts excellent mechanical properties,including a hardness of 360 HV and a wear rate of 2.4×10^(-5)mm^(3)·N^(-1)·mm^(-1).It also exhibits impressive yield strength,compressive strength,and deformation rates of 960 MPa,1,700 MPa,and 27.5%,respectively.

Microstructure and formability evolutions of AZ31 magnesium alloy sheets undergoing continuous bending process

Continuous bending (CB) process along rolling direction was performed to improve the formability of AZ31 magnesium alloy sheets. The microstructure and texture evolutions were characterized by optical microscopy (OM) and electronic backscatter diffraction (EBSD). The results reveal that the basal texture intensity of continuously bent and annealed (CBA) sample is drastically weakened. A large number of twins are induced on the concave surface by the 1st pass bending and the density of twins obviously declines during the 2nd pass bending owing to the occurrence of detwinning. Due to the asymmetric tension?compression strain states between the outer and inner regions during V-bending, twinning and detwinning are generated alternatively during the CB process. The Erichsen value is 5.2 mm which increases by 41% compared with that of as-received sample. This obvious improvement of formability can be attributed to the weakened basal texture, which leads to a smaller plastic strain ratio (r-value)together with a larger strain-hardening exponent (n-value).

Achieving strength-ductility synergy in novel paramagnetic Fe-based medium-entropy alloys through deep cryogenic deformation

Cryogenic pre-deformation treatment has been widely used to effectively improve the comprehensive mechanical properties of steels and novel metals.However,the dislocation evolution and phase transformation induced by different degrees of deep cryogenic deformation are not yet fully elucidated.In this study,the effects of multiple cryogenic pre-treatments on the mechanical properties and deformation mechanisms of a paramagnetic Fe_(63.3)Mn_(14-)Si_(9.1)Cr_(9.8)C_(3.8)medium-entropy alloy(MEA)were investigated,leading to the discovery of a pretreated MEA that exhibits exceptional mechanical properties,including a fracture strength of 3.0 GPa,plastic strain of 26.1%and work-hardening index of 0.57.In addition,X-ray diffraction(XRD)and transmission electron microscopy(TEM)analyses revealed that multiple cryogenic pre-deformation treatments significantly increased the dislocation density of the MEA(from 9×10^(15)to 4×10^(16)m^(-2)after three pretreatments),along with a transition in the dislocation type from predominantly edge dislocations to mixed dislocations(including screw-and edge-type dislocations).Notably,this pretreated MEA retained its paramagnetic properties(μ_(r)<1.0200)even after fracture.Thermodynamic calculations showed that cryogenic pretreatment can significantly reduce the stacking fault energy of the MEA by a factor of approximately four(i.e.,from 9.7 to2.6 m J·m^(-2)),thereby activating the synergistic effects of transformation-induced plasticity,twinning-induced plasticity and dislocation strengthening mechanisms.These synergistic effects lead to simultaneous strength and ductility enhancement of the MEA.

Improving the Intermittent Discharge Performance of Mg–Air Battery by Using Oxyanion Corrosion Inhibitor as Electrolyte Additive

A widely used oxyanion corrosion inhibitor（Li2CrO4） was used as electrolyte additive（3.5 wt% Na Cl solution was used as electrolyte solution） for Mg–air battery. The potentiodynamic polarization tests showed that the presence of 0.1 wt% Li2CrO4in the Na Cl electrolyte reduced enormously the corrosion current density of the tested AZ31 Mg alloys.According to the intermittent discharge tests, the use of 0.1 wt% Li2CrO4 as electrolyte additive increased the anode efficiency of the Mg–air battery by 28.4%. The addition of 0.1 wt% Li2CrO4reduced the anode self-corrosion rate of the battery in the intermittent stage effectively. The product film after discharge was observed by scanning electron microscope, and the Mg–air battery containing 0.1 wt% Li2CrO4has a loose product film, which is beneficial to its discharge performance. So using Li2CrO4 as electrolyte additive could improve the intermittent discharge performance of Mg–air battery. And the use of oxyanion corrosion inhibitor as electrolyte additive may be an excellent way to improve the intermittent discharge performance of Mg–air battery.

Influence of Grain Orientation on the Corrosion Behavior of Rolled AZ31 Magnesium Alloy

The effect of the grain orientation on corrosion behavior of rolled AZ31 magnesium alloy is investigated in this study. The test samples have a similar surface roughness to the Mg alloy in practical application. The immersion test and electrochemical impedance spectroscopy show that the TD-ND planes dominated by （101-0）, （1120） and （1011） oriented grains show a higher corrosion resistance compared with these of the RD-TD planes which consist mainly of （0001） oriented grains. Here, RD, ND and TD represent the rolling direction, the normal direction and the transverse direction of the alloy sheet, respectively. The surface morphologies of the alloys at various immersion stages are observed by scanning electron microscopy, and the surface topography of the alloy substitutes is also observed by laser scanning confocal microscopy. The TD-ND planes show a regular corrosion along the TD direction, but the RD-TD plane shows an irregular corrosion.