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Purpose This study aims to investigate the effect of microalloyed Ca and Ce on microstructure and corrosion behavior of Mg-1.5Zn alloy. Mg-1.5Zn-xCa-xCe alloys were prepared by melting, extrusion and rolling processes. Design/methodology/approach The effects of adding Ca and Ce elements alone or adding Ca and Ce elements simultaneously on the microstructure and corrosion resistance of Mg-1.5Zn-xCa-xCe (x = 0 or 0.2 Wt.%) alloys were studied by scanning electron microscopy, hydrogen evolution tests and electrochemical experiments. Findings The addition of Ca and Ce elements alone or the addition of Ca and Ce elements had little impact on the grain size of the rolled and annealed Mg-1.5Zn-xCa-xCe alloy, but had a greater effect on the type and quantity of the second phase. Originality/value The order of the corrosion rates for the three alloys was Mg-1.5Zn-0.2Ca < Mg-1.5Zn-0.2Ca-0.2Ce < Mg-1.5Zn-0.2Ce. Mg-1.5Zn-0.2Ca showed the best corrosion resistance, which was related to the second phase and corrosion products.

The microstructure and mechanical properties of Mg-1.5Zn-0.2Ca-0.2Ce alloy sheets processed via accumulated extrusion bonding (AEB) at 523 K were examined in this study. To investigate the microstructure evolution, samples corresponding to various process stages were taken from six locations parallel to the extrusion direction. Many twin boundaries were observed at the initial extrusion stage, and subsequently dynamic recrystallization (DRX) (especially ‘twin-assisted’ DRX and continuous DRX) was activated. With increasing strain, the matrix grains were gradually transformed into new DRXed grains, and the grains were significantly refined to 0.55 μm, whereas the grains grew to 3.1 μm outside the die. After the AEB process, the sheet exhibited almost the same texture as that of the as-received sheet with basal poles tilted to the extrusion direction by ~ ± 30°. The tensile test results revealed that, compared with the as-received sheet, the yield strength of AEBed sheets was improved as much as 50 MPa, resulting mainly from the grain refinement.

In this study, rolled AZ31 Mg alloy sheets were subjected to accumulated extrusion bonding (AEB) process at 473 K with transvers direction (TD) parallel (0°), at 45° inclined and perpendicular (90°) to the sizing band. Deformation and dynamic recrystallization (DRX) mechanisms of AZ31 Mg alloy sheets were investigated from start to end of AEB process. Mechanical properties of as-received and AEBed sheets were then evaluated by tensile tests based on the concurrent microstructure and texture evolution. The results indicated that {10–12} tensile twinning dominated the early stage deformation, and subsequently DRX occurred and dominated the further deformation. The effects of relative orientation on microstructure and texture evolution mainly occurred in the cone die and sizing band. 0° and 90° samples exhibited an ED-tilt double peak texture, and 45° sample showed a more disperse texture components in TD. After the extruded sheets exited from extrusion die, grain growth was observed with the orientations preserved from sizing band, and the interfaces of various samples were bonded successfully with different angles to TD. Mechanical properties tests indicated that three AEBed samples exhibited similar strength and ductility with higher yield strength (145 MPa vs. 169 MPa), ultimate tensile strength (336 MPa vs. 392 MPa), and fracture elongation (24.9% vs. 28.8%) comparing to that of as-received sample along RD.

Samples were cut from an extruded AZ31 magnesium alloy bar for uniaxial tensile and EBSD characterization tests. The long axis and bar extrusion directions were 0° (T0 sample), 45° (T45 sample), and 90° (T90 sample). The effects of loading direction on the tensile behavior, microstructure, and texture evolution of the magnesium alloy were studied. Results show that the obvious mechanical anisotropy of tensile behavior is affected by the loading direction, and the T0 sample with a grain c-axis perpendicular to the extrusion direction has a strong basal texture and high flow stress and yield strength. The loading direction has a significant influence on the microstructure characteristics of different samples, especially the number of {10–12} tensile twins and {10–11} compression twins. Texture evolution results show that the loading direction and the effect of deformation mode on the deformation mechanism lead to variations in texture evolution: the basal slip and prismatic slip during the plastic deformation of the T0 specimen, the compression twin of the T45 specimen, and the tensile twin of the T90 specimen.

Ultrafine-grained aluminum processed by a new severe plastic deformation technique, accumulative extrusion bonding (AEB), was investigated. Microstructural characterization indicated good interfacial bonding and an average grain size of ∼440 nm was obtained after six passes. Tensile testing revealed that the strength reached the maximum value of 195 MPa and the total elongation exceeded 16% after five passes. The hardness was also significantly improved and almost reached saturation after the first pass. SEM fractography of AEB-processed specimens after tensile test showed that failure mode was shear ductile fracture with elongated shallow dimples. Comparison with conventional accumulative roll bonding indicates that this new AEB technique is more effective in refining grain and improving mechanical properties of the specimens.

In order to improve the strength and ductility of AZ31 magnesium alloy thin sheet with thickness of 1.5 mm, an accumulated extrusion bonding (AEB) process was conducted for 1 and 2 passes at 473 K. Microstructure evolution and mechanical properties were subsequently investigated. The results showed that the interface bonded successfully with a good bonding quality due to the large strain induced by AEB process. {10–12} tensile twinning dominated the deformation at the initial stage of extrusion. As the strain increasing, dynamic recrystallization (DRX) occurred and dominated the further deformation. A fully DRXed microstructure was observed in the sizing band and the average grain size was significantly reduced to ∼1.4 μm. Grain growth occurred after the extruded sheet exited from extrusion die. AZ31 alloy sheet after by 1 pass AEB process exhibited a double-peak texture with the basal poles inclined from normal direction (ND) towards extrusion direction (ED) and showed a similar texture intensity to as-received sample. Due to the grain refinement strengthening, the AEB processed sample exhibited better comprehensive mechanical properties with a higher yield strength (169 MPa vs. 145 MPa), ultimate tensile strength (336 MPa vs. 385 MPa) and fracture elongation (24.9% vs. 28.0%) at room temperature. However, for the 2 passes extruded sample, the microstructure evolution and mechanical properties showed a similar characteristic to that of first pass sample. This indicated that increase in the number of AEB pass had no more effect on the grain refining and improving the mechanical properties.

Mg–3Al–1Zn alloy sheets have been deformed by continuous bending (CB) to investigate the effects of processing parameters (bending angle and repetitive passes) on the texture and formability. The samples exhibited a bimodal microstructure with abnormal growth grains in the surface region and fine grains distributed in the center after CB process followed by annealing. The texture evolution measured by XRD indicated that the basal poles were rotated from ND toward RD, and the texture intensity decreased with the bending angle decreasing and repetitive passes increasing. Compared with the as-received sample, the yield strength of CBA-120-2 sample significantly decreased from 183 to 112 MPa, and a smaller r-value and a larger n-value were obtained. The formability of CB processed samples in annealing condition was significantly enhanced with the highest of Erichsen value of 5.4 mm, increased by about 135%. The improvement of formability was likely attributed to the weakened and RD-tilt basal texture and coarse grains in the surface part.

A widely used oxyanion corrosion inhibitor (Li2CrO4) was used as electrolyte additive (3.5 wt% NaCl solution was used as electrolyte solution) for Mg–air battery. The potentiodynamic polarization tests showed that the presence of 0.1 wt% Li2CrO4 in the NaCl 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% Li2CrO4 reduced 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% Li2CrO4 has 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.

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).

To study the influence of blank holder type on the drawability of 5182-O aluminum sheet at room temperature, the flat blank holder and curved blank holder were employed during the deep drawing process. The microstructures were characterized by optical microscopy (OM). The results reveal that the limiting drawing ratio (LDR) of 5182-O aluminum alloy sheet is 1.7 using the flat blank holder. The drawn cup have severe earring. Compared with using flat blank holder, the LDR of 5182-O aluminum alloy sheet is enhanced to 2.0 using curved blank holder. In addition, the earring ratio also reduces and flange wrinkling is prevented when the curved blank holder is used. These are due to a more uniform sheet flow in different directions with curved blank holder.

In present work, the high strength-ductility balance of Mg-1.03Ca-0.47Mn Mg alloy sheet was successfully fabricated by rolling and annealing. After rolling, though the yield strength (YS) and ultimate tensile strength (UTS) of sheet were improved to 235 MPa and 253 MPa, the appearance of deformation-induced grain subdivision mechanism, shear bands and {10–12} extension twins also introduced strong (0001) basal texture with basal pole inclining to rolling direction which led the elongation (EL) decreased to 3.8%. As-annealed sheet occurred static recrystallization which led to the formation of finer grain structure than as-rolled sheet, and the strong (0001) basal texture of as-rolled sheet was transformed into weak (0001) peak texture with basal pole spreading widely along TD. Therefore, as-annealed sheet exhibits high strength-ductility balance with the YS of 235 MPa, UTS of 297 MPa and EL of 16.4%.

The effects of V-bending process, continuous bending process and combination process on the microstructure and mechanical properties and formability of an AZ31 magnesium alloy sheet were investigated. The experimental results showed that no twins were found in the microstructure of all samples after processes due to the fine grain. The V-bending and continuous bending processes were proved to be an effective approach to modify the mechanical properties and formability. While the samples after the combination process exhibited better mechanical properties and formability than the single processed sample. The yield strength significantly decreased with the value of 100 MPa and the fracture elongation enhanced to 18.3% at room temperature. The Erichsen value was 5.0 mm which was significantly increased by 117% compared with as-received sample. The superior formability of combination processed samples was mainly attributed to the smaller r -value and n -value.

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 $$(10\bar{1}0)$$ , $$(11\bar{2}0)$$ and $$(10\bar{1}1)$$ 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.

The effects of grain size on the shift of neutral layer of AZ31 magnesium alloy sheets with different grain sizes ranging from 12.1 to 34.7 μm were investigated by the 90° V-bending tests at 150 °C. The results show that the neutral layer tends to shift to outer region of the sheets and the coefficient of neutral layer value ( k -value) increases with the increasing grain size. This phenomenon is mainly owing to the enhanced asymmetry between the outer tension region and inner compression region with the increase of grain size. Twinning dominates the deformation in inner region while slips dominate the deformation in outer region. Key words: AZ31 magnesium alloy; grain size; V-bending; neutral layer; asymmetry 1 Introduction Due to the high specific strength, high stiffness and low density, magnesium alloy has been attracted by many industries, such as electron and automobile [1]. However, magnesium alloy has a hexagonal close- packed (HCP) crystal structure, so it performs a poor formability. According to von Mises criterion, it needs five independent slip systems to activate the deformation. Nevertheless, the basal plane is the main slip plane which can only provide two basal slips and the non-basal slip systems cannot be activated at low temperature [2]. So, there are few slip systems to coordinate the deformation along the

The effect of pre-compression deformation on the low-cycle fatigue properties and cyclic deformation behavior of as-rolled AZ31 alloy was investigated by performing the stress-controlled low-cycle fatigue tests at room temperature. Fatigue properties and cyclic damage process should be closely related to the twins. The present work aimed to investigate the deformation mechanism and fatigue life caused by the introduced {1 0−1 2} twinning–detwinning from the viewpoint of stress amplitude. The results reveal that the twins contribute to the fatigue properties and cyclic damage process of AZ31 alloy. There were noticeable changes in hysteresis loops, microstructures and fatigue lives when the stress amplitude increased from 120 to 150 MPa. The fatigue life of pre-compressed samples was more superior to that of the as-rolled sample under different stress amplitudes, especially under the stress amplitude close to the tensile yield strength of the as-rolled sample.

In this study, precompression deformation with a strain level of 5.38% along the transverse direction (TD) at room temperature was conducted on a AZ31 magnesium alloy thin sheet with thickness of 1mm. Then subsequent annealing treatment was carried out at various temperatures (200, 300, 400, and 500 °C) to induce static recrystallization (SRX) and grain growth. The stretch formability was also investigated using the hemispherical test. The results showed that the twinning texture induced by the precompression process was nearly inherited by recrystallized grains after annealing process. Grains grew up and the size increased with the increase of annealing temperature. The largest grain size was obtained when annealing at 400 °C. The mechanical properties including strength and ductility decreased due to the development of coarse grains, however, the stretch formability was enhanced significantly. Indeed, the IE-value increased from 2.83 mm in the as-received Mg alloy sheet to 5.78 mm in the precompressed and 400 °C annealed specimens, leading to an improvement of 104%. This was ascribed to the rotated grain orientation and higher activity of (10–12) twins in coarse grains.

In order to investigate the effect of twinning and detwinning on springback and shift of neutral layer, pre-stretch (PRS) of 3% and 5%, and pre-compression (PRC) of 1%, 3% and 5% along rolling direction was conducted in an AZ31 magnesium alloy sheets at room temperature. 90° V-bending tests were performed at 423 K with various pre-strained samples. The results show that springback increases after both PRS and PRC deformation. The coefficient of neutral layer ( k-value ) decreases with the increase of the levels of PRS and PRC. After PRS, twinning in an inner compressive region during bending is restrained and tension–compression asymmetry decreased. After PRC, detwinning occurs which implying that it dominates the deformation in the outer tensile region, while in inner compressive region twinning still governs the deformation. Twinning and detwinning leads to a decrease of asymmetry mechanism between the outer and inner layers. The decrease of asymmetry mechanism after PRT and PRC results in a drop of the neutral layer offset.