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The effect of intermediate rolling (IR) deformation on the microstructure and engineering critical current density, J_e (77K, 0T), has been investigated on Ag-sheathed Bi-2223 multifilamentary tapes. The experiment results showed that intermediate rolling reduces porosity, breaks down large deleterious secondary phases, and improves the alignment of Bi-2223 grains. All these effects strengthen the grain connectivity and therefore enhance the J_e value of the tape. Degradation in J_e with a further increase in IR reduction is caused by the introduction of more cracks that cannot be completely healed in subsequent heat treatment. J_e reaches a maximum value with an optimum IR reduction, which is determined by a competition between grain connectivity improvement and introduction of cracks. As a function of IR reduction, the degree of texturing in HTS oxide core also shows a similar peak value. XRD analysis demonstrates that the optimum IR reduction depends also on the volume fraction of Bi-2212 after the initial heat treatment.

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High quality YBa₂Cu₃O_7−x films on metallic substrates with high critical current densities well over 10⁶ A/cm² can be prepared by the rolling assisted biaxially textured substrates (RABiTS) method. Nickel or its alloys have been used as biaxially textured substrates formed through a specific rolling and high temperature annealing procedures. In this paper, we report a newly developed process for developing biaxial texture in rolled Ni tape by argon ion beam bombardment. It is named the ion-beam structure modification (ISM) process. In the ISM processed Ni foils, X-ray diffraction ω scans showed the full width-half maximum (FWHM) value of the (200) peak was 5.7°. And the electron back scattering diffraction (EBSP) analysis based on scanning electron microscopy showed good {100} 〈001〉 cubic orientation and the mean grain size was determined as about 25 μm. The texture evolution of rolled Ni foils during ISM process is reported also. For ISM process, local temperature elevation and distribution arises from the ion bombardment, coupled with anisotropic incident ion penetration and propagation as a result of channeling effects in the metal lattice, are expected to play the major roles in the development of grain reorientation in the Ni foil. Due to the simplicity and efficiency of the ISM process, the technique shows a great promise for application in the industrial scale production of long-lengths of superconductor tapes.

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The stability range of lead oxide compounds Pb₃Sr_2.5Bi_0.5Ca₂CuO_y (3321) phase and Ca₂PbO₄ phase in BSCCO materials has been investigated. In this study (Bi,Pb)₂Sr₂Ca₂Cu₃O_x (BSCCO) materials were heat treated in different oxygen partial pressure ranges from 1.0% O₂ to 20.8% O₂. The formation and decomposition of lead oxide compounds were determined by oxygen absorption and release processes, which were monitored with an oxygen analyzer. The phase composition was determined by X-ray diffraction. Experimental results show that the stability range of lead oxide compounds depends on the temperature and the oxygen partial pressure during heat treatment. Increasing oxygen partial pressure broadens the temperature range of the stable range of the (3321) phase, whereas the formation temperature of the (3321) phase remains at about 590 °C. Ca₂PbO₄ phase is more stable at higher temperature compared with the (3321) phase.

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Precursor powders containing different lead-rich phases: (a) Ca₂PbO₄, (b) Pb₃(Sr,Bi)₃Ca₂CuO_y (3321), were prepared by controlling the calcination temperature and atmosphere. Monofilament tapes were fabricated using those two powders. It has been found that both the microstructure and critical current depended strongly on the nature of the lead-rich phase. Tapes fabricated using the precursor with the Ca₂PbO₄ phase (tape T1) had a much lower optimum sintering temperature and a narrower temperature window than tapes fabricated using the precursor with the 3321 phase (tape T2). The critical current density J_c of tape T2 is improved by a factor 1.5–2. SEM results show that a large fraction of secondary phases with big particle size was formed in the fully reacted tape T1, which might degrade the critical current of these tapes. On the contrary, little and small secondary phases were formed in tape T2. It can be concluded that the control of the lead-rich phases present in the precursors is an effective way to improve the J_c values. The improvement in J_c of tape T2 is related to the improved grain connectivity, better texture of (Bi,Pb)₂Sr₂Ca₂Cu₃O_x grains as well as increased phase purity.

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The influence of precursor powders with different lead-rich phases, such as Ca₂PbO₄ and Pb₃(Sr,Bi)₃Ca₂CuO_y (3321), on the phase formation and critical current of Bi-2223/Ag tapes has been studied. Three precursors with different phase assemblages were prepared and used to make the tapes. The effects of different precursors were investigated by XRD, SEM/EDS and critical current measurements. It has been found that both the microstructure and phase formation depended strongly on the different lead-rich phases, which determined the reactivity of the precursor. Tapes fabricated using the precursor with Ca₂PbO₄ phase (tape T1) had lower transformation rate of 2223 phase than tapes fabricated using the precursor with 3321 phase (tape T2). SEM results show that a large fraction of secondary phases with big particle size was formed in the tape T1 during the subsequent sintering, which might degrade the critical current of the tapes. On the contrary, a small amount of secondary phases with small particle size was formed in the tape T2. Consequently, the critical current of tape T1 was lower than that of tape T2.

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The first production line of Bi-2223/Ag tapes in China has been installed in the end of 2001 with an annual production capacity of 200 km at Innova Superconductor Technology Co., Ltd. (Innost). Bi-2223/Ag tapes can be manufactured reproducibly with length up to 1 km, critical current I_c over 90 A (77 K, 0 T) and engineering critical current density J_e over 9 kA/cm². Innost's Bi-2223/Ag tapes are being used for producing China's first HTS power cable system (30 m, 3 phase, 35 kV/25 kA), which will be put into trial operation next year. Also, Innost's products will be used for other research projects of HTS applications such as HTS motor, HTS magnet and HTS transformer in China. In order to meet the requirements of HTS applications, tremendous research efforts have been made not only in enhancing the performance and uniformity of the Bi-2223/Ag tapes, but also in improving their application properties, which include reducing AC losses and thermal conductivity, increasing insulating properties and so on. Methods for improving productivity and yield will be also introduced.

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The effect of post-annealing on critical current density of (Bi,Pb)-2223/Ag tapes has been investigated. The fully reacted (Bi,Pb)-2223/Ag multifilament tapes were post-annealed in different processing parameters, including post-annealing temperature, dwelling time and oxygen partial pressure. Experimental results show that post-annealing at low temperature in reduced oxygen partial pressure can improve the critical current density. With decreasing oxygen partial pressure, the optimal temperature range of post-annealing shifts to lower temperature. The effect of post-annealing could be related to the increase of (Bi,Pb)-2223 phase and the formation of Pb₃Sr_2.5Bi_0.5Ca₂CuO_y (3321 phase) as well as the improvement of gain connectivity.

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Solution techniques are low cost non-vacuum methods for coated conductor development, which are promising in obtaining high quality YBa₂Cu₃O_7−x (YBCO) films. However, many pores and cracks are often formed in the YBCO film prepared by solution techniques, which degrades the film qualities. In this paper, we report a new method for modification of the structural and superconducting properties of YBCO film, namely, ion beam structure modification (ISM). Experimental results show that ISM is an effective way to eliminate the pores existed in solution deposited YBCO film. Denser and smoother films with improved c-axis grain alignment and grain connectivity have been obtained using ISM. The superconducting properties of the YBCO film are also improved.

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High purity rolled Ni substrate was annealed at 1000 °C for 60 min to develop a cube texture with a full-width at half-maximum (FWHM) value of 5.26°. Strontium acetate, titanium (IV) butoxide, and inorganic cerium nitrite were used as the starting materials for fabrication of SrTiO₃ and CeO₂ buffer layers via a sol–gel method on the Ni substrate material. The results show that the heat treatment temperature and holding time affect both the surface morphology and the texture of the buffer layers. The SrTiO₃ and CeO₂ buffer layers grown on the Ni substrate show a sharp (200) orientation distribution. An intermediate layer was found between the SrTiO₃ layer and the Ni substrate. By optimizing the heat treatment parameters, the ω-scan FWHM values can reach 5.31° and 6.60° for the SrTiO₃ and CeO₂ buffer layers, respectively.

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Fabrication of YBCO films on metal tapes by a full solution method is a promising technique for industrial application. For this process, the fabrication of suitably textured buffer layers is very important. In this paper, we report a new simple one-step heat treatment process, namely by the simultaneous texture (STEX) technique, for formation of textured buffer layers on cold rolled Ni tape by a sol–gel method. CeO₂ and Ba_0.5Sr_0.5TiO₃ (BST) buffer layers have been prepared using this new process. X-ray diffraction analyses show that the buffer layers are highly c-axis oriented. The FWHM values for ω and ϕ scans of the CeO₂ films are 4.09° (Ni: 4.77°) and 6.04° (Ni: 5.63°). The FWHM values for ω and ϕ scans of BST films are 8.01° (Ni: 7.78°) and 8.55° (Ni: 7.16°). A {100}〈001〉-cube texture was also formed in the rolled Ni substrate during the STEX process, indicating cube-on-cube texture formation by only a one-step annealing treatment. The possible mechanisms relating to cube-on-cube texture formation by a one-step annealing treatment are discussed.

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The development and stability of the cube texture formed during annealing has been investigated, using rolled nickel sheets of 99.95% and 99.999% purity. Microstructure and texture were characterized using electron back-scatter pattern analysis in the scanning electron microscope. The texture following primary recrystallization in both materials showed cube volume fractions of up to 50% and 80% (99.95% and 99.999% Ni respectively). The average grain size of the cube textured grains during recrystallization was larger than for grains of other orientations. For both materials high temperature annealing resulted only in normal grain growth, leading to a significant strengthening of the cube texture. The results are discussed in terms of the relative effects of size, boundary mobility and boundary energy on the process of grain growth. For the 99.999% Ni material an annealing process using a continuous heating ramp to 1200 °C gave a further improvement in the cube texture.

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Formation and growth of secondary phases in Bi-2223/Ag tapes have been investigated. Samples were heat treated at several temperatures for different periods under reduced oxygen partial pressure. The composition and microstructural evolution of secondary phases during the sintering process were characterized by SEM, XRD and EDS. Using high resolution SEM, the (Ca,Sr)₂CuO₃ (2:1), CuO and (Ca,Sr)₁₄Cu₂₄O₄₁ (14:24) phases could be clearly identified, and details of the Bi-2212, Bi-2223 structure, as well as the quenched liquid region could be also observed. Experiments showed the liquid region of quenched samples contained small Cu-rich precipitates, and the majority of the liquid was rich in Pb, Bi and Ca. The increase of the liquid region area fraction and the disappearance of the 2212 phase both take place quickly, in contrast to the slower development of the total secondary phase area fraction. The amount of the large secondary phase particles was lowest for samples sintered at 830 °C in 8.5% O₂. At higher temperatures, the amount of the 2:1 phase increased and the particle size of the 14:24 became larger, while at lower temperatures, the CuO particles appeared at very beginning and tended to grow rather fast.

▼ A honeycomb catalyst is prepared by supporting CuO and Na₂O on an Al₂O₃-coated cordierite ceramic for simultaneous SO₂ and NO removal from flue gas at 400^oC. Results show that (1) acid treatment of the substrate (cordierite ceramic) plays an important role in enhancing the catalytic activities; (2) coating of Al₂O₃ on the substrate shows an obvious promoting effect on both SO₂ and NO removal; (3) Na₂O addition significantly improves SO₂ removal activity but inhibits the selective catalytic reduction (SCR) activity of NO with NH₃. A catalyst containing 8.0wt.% Cu, 2.0wt.% Na and 21wt.% Al₂O₃ on the acid-washed cordierite ceramic shows good activities and stability in continued reaction-regeneration cycles, with a steady sulfur capacity of 4.4wt.% and steady-state NO conversion of about 90% at 400^oC and a space velocity of 2800h^-^1.

▼ The effects of chemical pretreatments of the support on CO oxidation over the activated carbon-supported Wacker-type catalyst were studied. Dry oxidation by air at 400^oC and wet oxidation in H₂O₂ and H₃PO₄ aqueous solution were used to modify the physical and chemical properties of activated carbon. The textural and surface characteristics of activated carbons were characterized by nitrogen adsorption, temperature-programmed desorption (TPD) and Boehm titration. The dispersion of active phase and chemical environment of CO oxidation catalysts were investigated by X-ray Photoelectron Spectroscopy (XPS) and temperature-programmed reduction (TPR). CO oxidation results showed that the catalyst prepared using activated carbon with high mesopores and oxygen-functional groups as support performs higher CO oxidation activity at ambient temperature, especially in high relative humidity. XPS and TPR results show that the activated carbon support with enriched oxygen-functional groups would benefit the distribution of active components (Pd^2^+, Cu^2^+) on the catalyst surface and the formation of easily reducible Cu^2^+ species.

▼ Al₂O₃-coated cordierite supported CuO catalyst shows high activities for selective catalytic reduction (SCR) of NO by NH₃ at 350-500^oC after being sulfated by SO₂. Its surface properties and reaction mechanism are elucidated in this paper by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) coupled with mass spectroscopy. Results show that the catalyst has both Lewis and Bronsted acid sites, the Bronsted acidity is far weaker than the Lewis acidity and the protonated ammonia on Bronsted sites is less stable than the coordinated ammonia on Lewis sites. Ammonia coordinated on sulfated CuAl₂O₄ may transfer to NH₂-NH₂, where aluminum species is responsible for NH₃ storage and copper species is responsible for activation of NH₃ to NH₂. The SCR reaction involves the adsorbed NH₂-NH₂ and gaseous NO, following Eley-Rideal mechanism. When NH₃ is insufficient, NO may convert to NO₂ through oxidation by O₂ or to N₂O and NO₂ through disproportionation.

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Effect of the evolution of the secondary phases in the first sintering process on the microstructure and critical current density of Bi-2223/Ag tapes has been studied. The amount and grain size of secondary phases were characterized by XRD and SEM/EDS. It has been found that both the microstructure and critical current of the fully reacted tapes depended strongly on the secondary phases formed in the first sintering process. The (Ca,Sr)₂CuO₃ and (Ca,Sr)₁₄Cu₂₄O₄₁ phases were easily formed and to be stable at higher temperature, however, at lower temperature, the CuO particles appeared easily and keeping stable with dwelling time. The best conversion to Bi-2223, together with the lowest amount of the total secondary phases was achieved when samples treated at 830°C in 8.5% O₂. Samples with the lowest amount and minimum size of secondary phase produced in the first sintering process will obtain the best performance of the fully reacted tapes. The optimum sintering parameters are obtained by controlling the evolution of the secondary phases during the first sintering process.

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Elliptical drawing (ED) dies were used during the manufacturing process of Bi-2223/Ag superconducting tapes and their influence on the tapes’ homogeneity and critical currents (I_c) has been investigated. By comparing two types of HTS tapes drawn by ED dies and a set of reference round dies, we found that the ED process can improve the qualities of the rolled tapes, such as improving the homogeneity of both the center and the peripheral filaments of the tapes, reducing the micro-cracks caused by the rolling process. Thus, the ED process can increase the I_c and engineering critical current density (J_e) values of HTS tapes.

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The effect of pre-annealing and pre-rolling (an initial rolling deformation prior to pre-annealing) on the final engineering critical current density J_e of Ag-sheathed Bi-2223 tapes has been investigated. The optimization of pre-annealing process was found to be dependent on annealing temperature much more than on oxygen partial pressure or soaking time. The highest J_e has been achieved for pre-annealing at 790°C for 20h in a flowing 8.5% O₂-balance N₂ atmosphere. Optical microscope and XRD rocking curve analysis show that pre-rolling improved the homogeneity of the tapes, reduced the sausaging effect and improved the texturing of the superconducting phase. All these effects strengthen the grain connectivity and further enhance the J_e value of the tapes. Too large a pre-rolling reduction, however, decreased the J_e owing to the introduction of more cracks that cannot be completely healed in subsequent heat treatment.

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Ag-sheathed Bi-2223 tapes were fabricated by a powder-in-tube technique with different configurations of the inner and outer sheath materials: Ag, Ag–Mg–Ni, Ag–Sb and Ag–Au. Characterization of thermal conductivity at 4.2 K to 100 K showed that the addition of Au decreased the thermal conductivity remarkably. The value at 40 K was 53.8 W/(mK) for AgAu–AgAu tape, five times lower than that of Ag–AgMgNi tape. The addition of Sb reduced AC losses much more than other alloyed element, partly due to its high electrical resistivity at 77 K. The measurement results of the normalized I_c dependence on magnetic field of the tapes indicated, however, no conclusive correlation between alloy type and I_c performance in field was highlighted. The mechanical property of alloy-sheathed tape was also evaluated. The sequence of the tapes’ tensile strength from highest to lowest was: Ag–Mg–Ni, Ag–Sb, Ag–Au, Ag.

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Commercial purity aluminum (99.5% Al) was deformed by equal channel angular pressing (ECAP) using up to 10 passes using route Bc. The evolution of microstructure and texture was characterized using the electron back scattered pattern technique. By use of the stereological parameter length per unit area (L_A), it was found that on average a sub-micron grain size is developed only after 10 passes. Significant heterogeneity exists however in the sample and in some places a sub-micron grain size is not developed even after 10 passes. The texture strength was found to increase with increasing strain over the strain range investigated. Comparison of microstructural evolution with other deformation modes suggests that ECAP is more similar to cyclic extrusion-compression than to cold-rolling.

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The dependence of flow stress (measured by tensile experiment) on the microstructure is discussed based on the Hall–Petch (H–P) relationship in interstitial-free steel cold-rolled to different reductions of 10–90%. The microstructure was characterized by TEM with semi-automated Kikuchi pattern analysis method. The significant effect of misorientation on the flow stress was found experimentally. The linear dependence of the slope of H–P relation on the average sub(grain) boundary misorientation is derived based on the work hardening dislocation mechanism. The modified H–P relation, i.e. σ_f=σ₀+K_H((θ_av/15)/d_subgrain)^0.5 is proposed to describe the effect of average misorientation on flow stress.

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The stability range of lead oxide compounds Pb₃Sr_2.5Bi_0.5Ca₂CuO_y (3321) phase and Ca₂PbO₄ phase in BSCCO materials has been investigated. In this study (Bi,Pb)₂Sr₂Ca₂Cu₃O_x (BSCCO) materials were heat treated in different oxygen partial pressures range from 1.0% O₂ to 20.8% O₂. The formation and decomposition of lead oxide compounds were determined by oxygen absorption and release processes, which were monitored with an oxygen analyzer. The phase composition was determined by X-ray diffraction. Experimental results show that the stability range of lead oxide compounds depends on the temperature and the oxygen partial pressure during heat treatment. Increasing oxygen partial pressure broadens the temperature range of the stable range of the 3321 phase, whereas the formation temperature of the 3321 phase remains at about 590 °C. Ca₂PbO₄ phase is more stable at higher temperature compared with the 3321 phase.

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A solution process was used for the epitaxial growth of CeO₂ seed layers and thin films on Ni substrate material using inorganic cerium nitrate as a precursor. The precursor solution was prepared by dissolving cerium nitrate in acetyl acetone, 2-methoxyethanol and glycol. The CeO₂ thin films, spin coated on Ni substrates, were annealed at 500–1100°C in a 4%H₂–Ar atmosphere. X-ray diffraction showed a strong c-axis orientation of the CeO₂ thin films on the Ni {001} (100) substrate. Out-of-plane and in-plane texture analysis, as well as pole-figure analysis, revealed a cube-on-cube texture in the films. For CeO₂ seed layers, scanning electron microscope investigations showed a discontinuous structure, whereas CeO₂ thin films possessed a continuous dense structure. A CeO₂ buffer layer grown on a CeO₂ seed layer showed an enhancement in the biaxial texture.

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The relationship between crystallographic orientation and the deformation microstructure formed during cold-rolling to high strains (up to ɛ_vM=4.5) has been investigated. The starting material was Ni (99.96% purity) with a coarse initial average grain size (approximately 500μm). Microstructural characterization was carried out using a combination of electron channeling contrast imaging and electron back-scatter diffraction orientation mapping. An orientation dependence of the deformation microstructure was observed even at the highest strain examined. A large increase in the average boundary misorientation is found at strains above ɛ_vM=1.8 for regions with the {112}〈111〉 and {123}〈634〉 orientations. This increase accompanies the structural transition from a medium strain microstructure to a high strain lamellar microstructure. In contrast, the average misorientation in regions of {110}〈112〉 orientation increases only slowly even up to the highest strain examined.

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The twinning and slip system activities during compression testing at room temperature and 150°C have been investigated for an AZ31 magnesium alloy. The samples, which were cut from a rolled sheet, were compressed with the compression axis taken at different angles to the sheet normal direction. The electron backscatter diffraction technique in the scanning electron microscope was used to investigate the local texture and microstructure evolution. The plastic deformation of magnesium is controlled by both Formula Not Shown twinning and slip during deformation. Extensive twinning takes place when the sample is loaded perpendicular to the basal plane normals (BPNs). A high work-hardening rate, with very little twinning, is observed for samples loaded parallel to the BPNs. The main features of the stress–strain curves can be explained based on the microstructural and texture data.

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Elastic and anelastic properties of TiN/a-Si₃N₄ and (Ti_1−xAl_x)N/a-Si₃N₄ superhard nanocomposite (nc) films prepared by plasma-induced chemical vapor deposition (PCVD), magnetron sputtering and vacuum arc deposition (physical vapor deposition, PVD) have been investigated by mechanical spectroscopy. One internal friction peak with relaxational nature was observed at temperatures around 230–280°C and frequencies about 100Hz for as-deposited films prepared by PVD, while no peak was detected in the films prepared by PCVD whose hardness was as high as 50GPa. A comparison of a series of samples indicates that the peak is higher for films with lower hardness. The activation energy and the pre-exponential factor of the relaxation time are deduced as 0.7–1.0eV and 10⁻¹⁰ to 10⁻¹²s, respectively. The intensity of this peak decreases with increasing annealing temperature. After annealing at 600–750°C, this peak disappears and Young’s modulus increases, in agreement with the increase in the hardness upon the annealing reported earlier. This internal friction peak is suggested to be associated with a thermally activated relaxation process within the interfaces that were not fully developed during the PVD process.

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The microstructural evolution in localized shear deformation was investigated in an 8090 Al–Li alloy by split Hopkinson pressure bar (strain rate of approximately 10³ s⁻¹) at ambient temperature and 77 K. The alloy was tested in the peak-, over-, under-, and natural-aged conditions, that provide a wide range of microstructural parameters and mechanical properties. Two types of localized shear bands were distinguished by optical microscopy: the deformed shear band and the white-etching shear band. They form at different stages of deformation during localization. There are critical strains for the occurrence of deformed and white-etching localized shear deformation, at the imposed strain rate. Observations by transmission electron microscopy reveal that the white-etching bands contain fine equiaxed grains; it is proposed that they are the result of recrystallization occurring during localization. The deformed-type bands are observed after testing at 77 K in all heat treatment conditions, but they are not as well defined as those developed at ambient temperature. Cracking often occurs along the localized shear at ambient temperature. The decrement in temperature is favorable for the nucleation, growth and coalescence of the microcracks along the shear bands, inducing fracture.

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Al–1wt%Mn single crystals of {001}〈110〉 orientation have been rolled to 30 and 50% reductions under controlled homogeneous rolling conditions. The local orientations have been measured by the electron back-scattered pattern (EBSP) technique and a semi-automatic TEM method over different scales. EBSP orientation image maps (OIMs) based on the local orientation data and TEM micrographs were used to reveal the deformation structure. It was found that the crystals subdivided into different macroscopic regions across the specimen thickness and significant microstructural difference was observed in regions with different macroscopic orientations. Good agreement was revealed by comparison of the results concerning microstructure and local crystallography obtained from EBSP and TEM measurement.

▼ Polycrystalline pure aluminium (99.99%) has been deformed at room temperature by the Cyclic-Extrusion-Compression (CEC)-method to strains in the range 0.9-60 (1-67 cycles). At different strains, the microstructure and local crystallography have been characterised in particular by transmission electron microscopy. It has been found that the microstructure develops from a cell block structure into an almost equiaxed structure of cells and subgrains, that the spacing between the boundaries subdividing the structure is almost unaffected by the strain and that the misorientation across these boundaries increases with the strain over the whole strain range. At the largest strain, the average misorientation across the deformation induced boundaries is ~25^o. The flow stress in compression is measured after the cyclic deformation and it is found that the flow stress increases with strain towards a saturation level which is reached at a relatively low strain. The discussion comprises the effect of deformation mode and plastic strain over a large strain range on the microstructural evolution and mechanical behaviour of aluminium.

▼ We report microstructure evolution and mechanical property of Mg alloy AZ31 processed by a new deformation technique, dual-directional extrusion (DDE). Using optical microscopy, scanning electron microscopy, and electron back scatter diffraction technique, we attribute the significant refinement of original coarse grains in the DDE-processed alloy to the occurrence of dynamic recrystallization. Moreover, we find that low temperature is crucial for yielding fine grain, which consequently results in high micro-hardness and yield stress, large fracture strain, and enhanced elongation. The improved mechanical properties are comparable or even superior to those of the alloy subjected to other deformation techniques, rendering the DDE a promising way for further tailoring properties of Mg-based alloys.