Activation Of Non-basal Slip Research Articles

Achieving excellent ductility with increased Schmid Factor but decreased direct strain contribution of basal slip in an intergranular misorientation tailored magnesium alloy

Weakening the basal texture was a commonly used method to improve the ductility and formability of magnesium alloys. The easier activation of basal slip was often considered to be an important reason for the improved ductility of the weak basal textured magnesium alloys. However, basal slip alone cannot well satisfy the Von Mises criterion and its activation was nearly saturated in strong basal textured magnesium alloys. The deformation mechanisms of weak basal textured magnesium alloys are still open to debate. In this work, the Schmid Factor (SF) of the basal slip is obviously increased and a high fracture elongation of ∼35% is achieved in AZ31 alloy by careful tailoring of grain orientation and rational selection of loading direction. Grain size scale strain distribution by high-resolution digital image correlation (DIC) and slip activation based on the slip trace method were used to in-depth analyze the deformation mechanisms. Although the basal slip’ average SF increases, the strain statistics show that the direct strain contribution of the basal slip to the deformation gets decrease, contrary to conventional expectation. This is mainly attributed to the coupling effect of the increased basal slip’ SF with the large intergranular misorientation, which significantly promotes the activation of non-basal slip and increases its contribution to the deformation, thus leading to a lower direct strain contribution of the basal slip. The results of the study may help to further reveal the plastic deformation mechanism of magnesium alloys and improve the plasticity of magnesium alloys.

Synergistic effect of Gd and Ce on enhancement of mechanical properties of as-extruded Mg-Sn-Zn alloys

The effects of incorporating dilute Gd and Ce on the microstructure and mechanical properties of Mg-0.5Sn-0.3Zn (TZ00, wt%) alloys are systematically revealed. The results indicate that the co-addition of 0.3 wt% Gd and 0.3 wt% Ce can significantly reduce the grain size from 40.8 μm to 12.0 μm, enhance dynamic recrystallization, and attenuate the intensity of basal texture. Furthermore, plenty of micron- and nano-scale (Gd, Ce)MgSn phases are precipitated. In comparison with the TZ00 alloy, the Mg-0.5Sn-0.3Zn-0.3Gd-0.3Ce alloy (TZGE0000, wt%) displays synergistic improvements in strength and ductility. The corresponding tensile yield strength (TYS), ultimate tensile strength (UTS), and elongation (EL) are 214.1 MPa, 297.4 MPa, and 23.5 %, respectively. The primary reason for this strength improvement is the combined effects of grain refinement and (Gd, Ce)MgSn nano-phase strengthening, while the ductility enhancement is mainly due to the refined grain size, weakened basal texture, increased activation of prismatic slip and {10−12} tensile twinning. Additionally, relative Visco-Plastic Self-Consistent (VPSC) simulations confirm that the combined addition of Gd and Ce can promote the activation of non-basal slip and {10−12} tensile twinning during the deformation process. In more detail, basal and prismatic slips are the primary deformation mechanisms during tensile loading, together with a minor occurrence of {10−12} tensile twinning and pyramidal slip coordination deformations. Conversely, {10−12} tensile twinning predominates during the compression deformation.

The dependence of Zener-Hollomon parameter on softening behavior and dynamic recrystallization mechanism of a biodegradable Zn-Cu-Mg alloy

The Zn-Cu-Mg alloy exhibits good strength, ductility, anti-aging and antibacterial properties, which lays the foundation for developing high performance Zn-based biodegradable alloys. However, the constitutive equation and dynamic recrystallization (DRX) behavior of this alloy remain unclear, making the optimization of hot processing parameters almost dependent on trial and error. This work aims to address these issues by investigating the hot compression process. The calculated average activation energy Q of this alloy is 141.338 KJ⋅mol-1, exhibiting excellent heat resistance. The deformed microstructure strongly depends on the Zener-Hollomon parameter (Z=ε˙exp(QRT)). Discontinuous DRX (DDRX) dominates at low lnZ, which has a significantly different orientation from the parent grain. Continuous DRX (CDRX) occurs within the grain and at grain boundaries, and is dominant at middle lnZ, mainly through activation 〈a〉 or/and 〈c+a〉 slip systems. Additionally, the activation of prismatic slip further promote CDRX, and most CDRX grains inherit the 30°[0001] orientation from the parent grains. The volume fraction of DRX demonstrates a decreasing trend followed by an increasing trend with increasing lnZ. At high lnZ, the increase of DRX grains is conducive to weakening the texture, and twin-induced DRX (TDRX) is significantly promoted, leading to an increase in both peak stress and strain hardening rate. Furthermore, the grains with c-axis aligned parallel to the compression direction (CD) are more prone to twinning, while the c-axis perpendicular to CD are the hard orientation of basal slip and compression twins. TEM results reveal that a decrease of c/a value promotes the activation of non-basal slip near the twin boundary, and the highly active 〈c〉 and 〈c+a〉 slips contribute to the increase of strain hardening rate. The results of this study are significant for understanding the workability of Zn-Cu-Mg alloys at high lnZ due to its high efficiency and low cost.

Preparation of ultra-high ductility and high strength Mg-Sn-Zn-Zr alloy by differential thermal ECAP (DT-ECAP) induced heterogeneous structure

Developing high-ductility magnesium (Mg) alloys has become an imminent issue for their wide application. In this work, a new Mg-Sn-Zn-Zr alloy with ultra-high ductility (elongation, El. over 40 %) and high ultimate tensile strength (UTS, ∼309–354 MPa) was prepared by a novel differential thermal equal-channel angular pressing (DT-ECAP). Heterogeneous structures, including bimodal grain structures and inhomogeneous distribution of second phases composed of banded structure and particle free zone (PFZ), were induced by DT-ECAP process. Based on the results of electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and selected area electron diffraction (SAED), the bimodal grain structure originated from incomplete dynamic recrystallization (DRX) dominated by Zener pinning, strain-induced grain boundary migration (SIBM) and the limitation of polycrystallization due to lower dislocation density. Meanwhile, the bimodal distribution of second phases was highly associated with the defect density and initial structure. More importantly, the enhanced strength of DT-ECAPed alloys can be primarily attributed to hetero-deformation induced (HDI) strengthening, grain boundary strengthening, and precipitation strengthening. Moreover, HDI hardening, texture weakening or randomizing activation of non-basal slip, high density of dislocations in sub-structures, and twining induced superior work-hardening effect, which was highly responsible for the ultra-high ductility in sixth pass (6P) alloy. The current work provides a novel DT-ECAP process for inducing heterogeneous structure and offers beneficial insight into the development of ultra-high ductility and high strength for rare-earth-free Mg alloys via a combination of HDI strengthening and hardening and other vital mechanisms.

A comparative study on the effect of 0.5 wt% Ca or Ce on the microstructure, texture, and mechanical properties of the hot-rolled Mg-4Li alloy

The microstructure, texture, and mechanical properties of the hot-rolled Mg-4Li, Mg-4Li-0.5Ca and Mg-4Li-0.5Ce alloy were examined. The results indicated that the addition of either Ca or Ce significantly refined the microstructure and largely randomized the texture distribution of as-rolled Mg-4Li. Meanwhile, Mg-4Li-0.5Ca exhibited a relatively smaller grain size and a more scattered texture distribution compared to Mg-4Li-0.5Ce, probably attributed to the more prominent recrystallization in Mg-4Li-0.5Ca. Additionally, owing to the more refined microstructure and dispersed Mg2Ca, the strength of Mg-4Li-0.5Ca is much higher than that of Mg-4Li-0.5Ce, while both of them are superior to the counterpart of Mg-4Li. Moreover, by benefiting from the enhanced activation of non-basal slip, Mg-4Li-0.5Ce exhibits a much larger elongation compared to Mg-4Li. However, the elongation of Mg-4Li-0.5Ca is slightly lower than that of Mg-4Li, potentially ascribed to the occurrence of preferred cracking within the eutectic-like Mg2Ca.

Improvement of strength and ductility of TC4p/AZ91D magnesium matrix composites by modifying the extrusion ratio

In this study, AZ91D (Mg-9Al-Zn) alloys reinforced with 2 vol% TC4 (Ti–6Al–4 V) particles fabricated by semi-solid stir casting were extruded at different ratios, resulting in observed grain refinement effects. The research findings demonstrate that both TC4 and β-Mg17Al12 phases contribute to promoting dynamic recrystallization (DRX) nucleation. With increasing extrusion ratio, the β-phase (Mg17Al12) gradually fractures into smaller particles, leading to progressive grain refinement. Furthermore, the transition from 〈01–10〉 fiber texture to non-basal texture in the α-Mg matrix after hot extrusion is attributed to improved DRX behavior and activation of non-basal slip. As the extrusion ratio increases, the tensile strength and elongation (EL) of TC4p/AZ91D composite improve significantly, reaching optimum comprehensive mechanical properties at an extrusion of 40:1 with a yield strength (YS) of 257 MPa, an ultimate tensile strength (UTS) of 357 MPa, and an EL of 9.7%. This remarkable strengthening effect is primarily attributed to β-phase reinforcement, grain refinement strengthening, and strain hardening.

Effect of extrusion ratio on microstructure, texture, and mechanical properties of dual-phase Mg−8Li−6Zn−2Gd alloy

The microstructure observation, macrotexture analysis, and tensile test were conducted to investigate the effect of extrusion ratio on the microstructure, texture, and mechanical properties of Mg−8Li−6Zn−2Gd alloy. The results show that the as-homogenized Mg−8Li−6Zn−2Gd alloy consists of α-Mg, β-Li, MgLiZn, I-phase, and W-phase. After hot extrusion, eutectic I-phase is broken into fine particles, while W-phase maintains massive shape. Both α-Mg and β-Li matrices undergo dynamic recrystallization (DRX), and their grains gradually refine with increasing extrusion ratio. For α-Mg matrix, the weakening of basal texture and the strengthening of prismatic texture after hot extrusion are due to the activation of non-basal slip. For β-Li matrix, the appearance of obvious α and γ fiber textures after hot extrusion is associated with the dynamic recovery (DRV) and DRX. The tensile strength and elongation of the alloy are simultaneously improved by hot extrusion, and the best comprehensive mechanical properties are achieved when extrusion ratio is 16:1.

Ductility enhancement by activating non-basal slip in Mg alloys with micro-Mn

The effect of micro-Mn addition on the microstructure and mechanical properties of Mg alloys was analyzed. Electron back scattered diffraction, slip traces analysis, transmission electron microscopy and visco-plastic self-consistent polycrystal constitutive modeling were performed to investigate the deformation mechanisms in the tensile test. The results show that the average grain size of Mg−Mn alloys decreases from 28.30 to 5.10 μm with Mn addition. Furthermore, with the increment of Mn content, the ductility of the as-extruded samples improves from 14.33% to 20.33%, and the yield strength increases from 84 to 180 MPa. The reason for this simultaneous improvement is that the critical resolved shear stress gap between basal slip and non-basal slip decreases from 173 to 115 MPa, which leads to the increase of non-basal slip activity. The adjustment of slip system difference by microalloying elements provides a way to develop Mg alloys with high strength and ductility.

Effect of microstructure on the deformation of as-cast [formula omitted]-Mg/LPSO two-phase alloys: An integrated SEM-DIC and crystal plasticity study

The present work investigates the plastic deformation of as-cast Mg/LPSO two-phase alloys with varying LPSO phase volume fractions through a combination of SEM-DIC and CPFE simulations. To this end, the same microstructures observed experimentally were numerically deformed and the predicted strain fields were compared to the experimental ones. The reasonable agreement between the simulations and the experiments confirmed that basal slip in LPSO grains is the prevalent deformation mechanism. Besides, analysis of the experimental strain field in LPSO grains suggested that the relevant length scales governing the strength of basal and non-basal slip in LPSO grains were the LPSO length parallel to the basal plane and the LPSO width perpendicular to it. Finally, discrepancies in terms non-basal slip activity were suggested to be due to an overestimation of the strength of prismatic slip combined with the omission of first-order pyramidal slip in the modeling hypotheses. This study sheds light on the complex interplay between microstructure and deformation mechanisms in Mg/LPSO two-phase alloys. It emphasizes the importance of considering multiple slip modes and accurate CRSS values when modeling such systems. Additionally, it highlights the valuable insights that can be gained through a combination of experimental and computational approaches in understanding localized strain behavior.

Achieving extraordinary strength-plasticity synergy in AZ91 alloy processed by multi-degrees of freedom forming

Strength and plasticity trade-off in magnesium alloys is a longstanding and crucial issue that significantly limits their application, which strongly relates with microstructure distribution and texture characterization. In this study, multi-degrees of freedom forming (multi-DOF forming) technology is innovatively proposed and first employed on as-extruded AZ91 alloy. Microstructure observation reveals that the bimodal-grained structure including 25.4 % of coarse grains (CGs, ∼20 μm) and 74.6 % of fine grains (FGs, ∼2 μm) in volume fraction is fabricated in the multi-DOF formed AZ91 alloy, which is mainly attributed to inhomogeneous dynamical recrystallization (DRX), i.e., un-recrystallized plays a leading role in CGs and DRX plays a leading role in FGs. Grain orientation analysis indicates that multi-DOF forming technology leads to a significant disappearance of basal texture, bringing out the absolute predominance of prismatic texture with 83.4 % in volume fraction, which is mainly owing to the introduction of large radial-tangential coupling shear deformation and thus efficient activation of non-basal slips in magnesium alloys. Moreover, the Multi-DOF formed AZ91 alloy exhibits high ultimate tensile strength (∼402 MPa) without sacrificing elongation (∼18.1 %), realizing extraordinary strength-plasticity synergy. The high work-hardening capacity resulting from high geometrically necessary dislocations at the interface of CGs/FGs is conducive to the improved strength. The higher Schmidt factor in grains with bimodal-grained structure or non-basal texture dramatically contributes to the enhanced plasticity. Thus, we propose a novel and effective multi-DOF forming technology for achieving concurrent enhancement of strength and plasticity in magnesium alloys.

The discrepancy in basal slip hardening rates of cast and extruded Mg-Y-Zr alloys

The differences in the deformation mechanisms during uniaxial tension of cast and extruded Mg–2Y-0.5Zr (wt%) alloys have been investigated by using EBSD-based slip trace analysis and VPSC simulation methods, and a novel method for counting the activity of slip/twinning using grain area has been proposed. Slip trace analysis reveals that enhanced ductility and reduced tensile-compressive asymmetry observed in the Mg–2Y-0.5Zr (wt%) alloy can be attributed to the addition of the Y element, which modified the texture, and promoted pyramidal <c + a> slip and suppressed prismatic <a> slip. The extruded alloy exhibits a distinctive pseudo-fiber bimodal microstructure, which contributes to its superior ductility. The VPSC results indicate that the CRSSnon-basal/CRSSbasal ratio of the extruded alloys decreases, whereas the CRSStwinning/CRSSbasal ratio increases, which is attributed to the different effects of the grain refinement on the different deformation modes. In addition, both the VPSC results and the slip trace analysis results indicate that the extruded alloy exhibits reduced non-basal slip activity compared to the cast alloy at similar strain levels. The work-hardening rate curves and VPSC parameters give a reasonable explanation that the key to the increase in the ductility of Mg–Y–Zr alloys after extrusion is the decrease in the basal hardening rate rather than the non-basal slip activity. The refinement of grain size leads to a significant decrease in basal slip hardening rate, primarily due to the decrease in the additional hardening effect caused by tensile twinning and the generation of an additional GBS mechanism in the pseudo fiber microstructure.

Enhanced strength-ductility synergy and activation of non-basal slip in as-extruded Mg–Zn–Ca alloy via heterostructure

The relationship between the heterogeneous grain structure and mechanical properties is an emerging aspect of the effort to expand the applications of Mg alloy. In this study, heterostructured Mg alloy, comprising elongated and fine equiaxed grains, was fabricated through a simple hot-extrusion process with extrusion temperature of 320 °C. This resulted in a yield strength (YS) of approximately 192 MPa and excellent elongation of approximately 20.4 %. When compared to the alloy extruded at 360 °C, which had a homogenized structure, the increased YS in the 320 °C extruded alloy was primarily attributed to hetero-deformation-induced (HDI) strengthening. The inclusion of Zn and Ca, along with stress concentration, promoted active <c+a> slips, thereby enhancing the ductility of the alloy extruded at 320 °C. This endeavour provides an inspiring strategy for improving the YS of Mg–Zn–Ca alloys without significantly compromising ductility.

Deformation mechanism of high ductility Mg-Gd-Mn alloy during tensile process

In this research, a high ductility Mg-Gd-Mn magnesium alloy was designed and developed, with an elongation capability surpassing 50%. To gain insights into the underlying mechanism behind the high ductility of the Mg-2Gd-0.5Mn alloy, quasi-in-situ electron backscattered diffraction and two-beam diffraction were conducted. The results reveal that the Mg-Gd-Mn alloy exhibits a distinct rare-earth texture, and the activation of non-basal slip systems is evident from the clear observation of non-basal slip traces during the later stages of deformation. However, the primary deformation mechanisms in Mg-Gd-Mn alloy remain basal <a> slip and {10–12} tensile twinning, and the remarkable ductility observed in Mg-Gd-Mn alloys can be attributed to the softening of non-basal slip modes, which leads to a coordinated deformation between various modes of deformation. To further validate this conclusion, an analysis was conducted using a visco-plastic self-consistent (VPSC) model to investigate the relative activity of basal and non-basal slip in Mg-Gd-Mn alloys. The obtained results align well with experimental observations, providing additional support for the hypothesis.

Towards strength-ductility synergy in a weak-textured Mg–3Y extruded sheet via pre-twinning and annealing

Mg-RE (magnesium-rare earth) binary alloys, such as Mg–Y alloys, usually exhibit weakened texture and excellent plasticity compared with traditional RE-free Mg alloys. However, the weakened texture could lead to a significant decrease in the strength of Mg-RE binary alloys. In this work, the weak-textured Mg–3Y (wt. %) extruded sheet displayed good strength-ductility synergy with a 41% increase in the yield strength and a good ductility similar to the initial sheet via simple pre-twinning and annealing treatment (PT). After PT, the average grain size of the sheet decreased from 11.2 μm to 6.0 μm and 34.2% initial soft texture component (<11–21> //normal direction (ND)) was transformed into the hard texture component (<0001> //transverse direction (TD)). The effect of pre-twinning on deformation mechanisms was systematically investigated by slip trace analysis and activation stress (τ) analysis. Basal slip was the dominant deformation mechanism during the tension of the as-extruded (AE) specimen while pre-twinning promoted the activation of non-basal slip, especially prismatic slip in the PT specimen. The texture transformation and reduced critical resolved shear stress (CRSS) ratio between non-basal slip and basal slip induced by pre-twinning were primarily responsible for the high activity of non-basal slip. The underlying strengthening mechanism and the reason for good ductility were also rationally discussed. The strengthening effect of single grain refinement was relatively lower in the weak-textured Mg–3Y alloy. Texture hardening could effectively improve the effect of fine-grain strengthening. The excellent deformation compatibility between basal slip of parent grains and prismatic slip of twins as well as relatively higher activity of the second-order pyramidal slip was the origin of the good ductility of the PT specimen.

Texture weakening and grain refinement behavior of the extruded Mg-6.03Zn-0.55Zr alloy during hot plane strain compression

A series of hot plane strain compression (PSC) experiments of the extruded Mg-6.03Zn-0.55Zr alloy were conducted on the Gleeble-3500 machine with strain rates of 0.01 s−1 to 10 s−1 and temperatures ranging from 300 °C to 500 °C to reveal the microstructure evolution during the secondary process. The effects of grain refinement and texture modification which were easily affected by the deformation mechanism and dynamic recrystallization (DRX) were systematically studied. Experimental results showed that the main deformation mechanism during PSC was basal <a> slip (74.3 %–94.9 %) and assisted by prismatic <a> slip (4.8 %–21.1 %) and pyramidal <c+a> slip (0.3 %–4.6 %). Since the pyramidal <c+a> slip and prismatic <a> slip were more preferred to activate owing to the significant decrease of critical resolved shear stress (CRSS) at a higher temperature, the activation of non-basal slip promoted the c-axes of the grains deviated from compression direction which weakened the basal fiber texture. Moreover, the activation of non-basal slip could promote DRX behavior to some extent. Further analysis of the DRX mechanism showed that the continuous DRX (CDRX) by continuous rotation of low angle grain boundaries was dominant at lower temperatures and higher strain rates, while discontinuous DRX (DDRX) which nucleated at the grain boundaries played a more and more important role as the temperature increased and strain rate decreased. After characterizing the orientations of the DRXed grains, the CDRXed grains owned a similar grain orientation with the deformed grain while the DDRXed grains exhibited a fairly dispersed distribution, indicating that the weakening effect of the basal texture was greater with a higher DDRX fraction.

Effect of deformation mode on double-peak texture evolution in pre-twinning Mg-3Al-1Zn alloy during high-speed impacting loading

An investigation of the quantitative effect of the deformation process on the deformation mode, texture evolution, and their internal relationship could help control the mechanical properties of targeted materials. In this study, the deformation mechanism and texture evolution of pre-twinning AZ31 magnesium alloy under medium temperature with high-speed impact loading are investigated through electron backscattered diffraction and the coupled simulation of the finite element method and viscoplastic self-consistent models. Basal and < c + a > pyramidal slips are the dominant accommodation modes. The activation of nonbasal slip is promoted, and the number of twins increase with an increase in the impact pressure, leading to a decrease in the relative activity of the basal slip. Based on typical grain rotation statistics, the effects of basal slip, pyramidal <c + a> slip, and extension twins on grain rotation are studied. With an increase in the pressure, the relative activity difference between the basal slip and pyramidal <c + a> glide decreases, which is beneficial for the formation of a double-peak basal texture and the enhancement of the intensity of the double-peak texture. The twin density affects the split angle between the double peaks.

In-situ investigate on the microstructure evolution, deformation and fracture mechanism of Mg-Gd-Zn-Mn alloy with varies of LPSO volume fraction

The induction of long-period stacking ordered (LPSO) phase through heat treatment was an effective method to strengthen magnesium alloys. In this study, the volume fraction of lamellar LPSO in the Mg-4Gd-1Zn-0.5Mn alloy was controlled by optimizing the heat treatment process. The research findings showed that with increasing heat treatment time, the volume fraction of LPSO initially increased then decreased until disappearing. The alloy treated at 500 °C for 2 h exhibited the highest volume fraction of lamellar LPSO, increasing from 1.64% to 13.68%. Further in-situ tensile tests were conducted on two types of alloys contain higher LPSO fraction (HL) and lower LPSO fraction (LL) at ambient temperature. The increased critical shear stress (CRSS) and obstacle effects on dislocations caused by LPSO effectively enhanced the strength of the alloy. The dominant deformation mechanisms of both HL and LL alloys are basal slip and twinning during tensile deformation. However, the HL alloy activated more non-basal slip significantly, which was ascribed to the activation of non-basal slip by LPSO kinking during deformation. Additionally, the bending and kinking of LPSO effectively restricted crack initiation and propagation, thereby enhancing the plasticity. The HL alloy exhibited fewer twin boundaries after deformation, which was attributed to the hindrance of twinning extension by LPSO.

Enhanced deformability of WE43 magnesium alloy by activation of non-basal slip and twinning deformation modes in the equal channel angular pressing at room temperature

Activation of the prismatic and pyramidal slip systems, along with the twinning as the secondary deformation mechanism, assists in the accommodation of a larger plastic strain during the deformation of magnesium alloys. In this paper, deformation mode activity and texture evolution of the WE43 magnesium alloy were investigated during core-sheath equal channel angular pressing (ECAP) at room temperature. Texture studies and transmission electron microscopy inspections suggest that the mechanisms behind the ECAP at room temperature assisted by back pressure were activation of (101¯0) prismatic slip (as the primary mechanism), as well as extension and contraction twinning.

The improvement on mechanical anisotropy of AZ31 magnesium alloy sheets by multi cross-rolling process

The rolled AZ31 Mg alloy sheets were manufactured by unidirectional rolling and cross-rolling with two passes and five passes in this study. The improvement of multi cross-rolling on the anisotropy of mechanical properties, microstructure and texture of AZ31 Mg alloys was investigated by tensile fracture experiments, optical microscopy (OM) and electron backscatter diffraction (EBSD). The results indicate that the samples after rolling which were rotated by 90° showed weaker anisotropy than the samples rolled by 0° path. The ultimate tensile strength of the samples after 0° direction rolling increased from 236 MPa to 338 MPa on the transverse direction (TD) compared to as-rolled samples. The ultimate tensile strength of unidirectional rolling samples with two and five passes paralleled to TD is increased by 7% and 14% than that of cross-rolling samples. The enhanced mechanical properties are attributed to fine-grained strengthening, twin strengthening and dislocation strengthening. The {10−12} extension twin, {10−11} contraction twin and {10−12}-{10−11} double twin were investigated in the microstructure of samples by multi cross-rolling. All the samples showed the basal texture on the {0001} < 11–20 > . The basal texture of cross-rolling samples was apparently weakened for comparison to unidirectional rolling samples and the basal texture of five-pass cross-rolling samples was weaker than that of two passes. The improvement of anisotropy after cross-rolling can be attributed to grain refinement, the activation of non-basal slip and the weakening of basal texture.

Improving the Mechanical Properties of Mg-5Al-2Ca-1Mn-0.5Zn Alloy through Rotary Swaging.

To meet the demand for more extensive applications of Mg alloys, a Mg-5Al-2Ca-1Mn-0.5Zn alloy without RE was prepared in this paper, and its mechanical properties were further improved by conventional hot extrusion and subsequent rotary swaging. The results show that the hardness of the alloy decreases along the radial central region after rotary swaging. The strength and hardness of the central area are lower, but the ductility is higher. The yield strength and ultimate tensile strength of the alloy in the peripheral area after rotary swaging reach 352 MPa and 386 MPa, respectively, while the elongation remains at 9.6%, exhibiting better strength-ductility synergy. The grain refinement and dislocation increase caused by rotary swaging promoted strength improvement. The activation of non-basal slips during rotary swaging is an important reason for the alloy to maintain good plasticity while improving strength.