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Due to their excellent strength-to-weight ratio, Mg alloys are attractive for applications where weight savings are critical. However, the limited cold formability of wrought Mg alloys severely restricts their widespread usage. In order to study the role that deformation twinning might play in limiting the elongation-to-failure ( $${\varepsilon} _{\text {f}}$$ ), in-situ tensile tests along the extrusion axis of Mg-1Mn (wt pct) were performed at 323 K, 423 K, and 523 K. The alloy exhibited a strong basal texture such that most of the grains experienced compression along their $$\langle {c}\rangle $$ -axis during deformation. At 323 K, fracture occurred at about 10 pct strain. Although basal, prismatic, and pyramidal $$\langle {c+a}\rangle $$ slip activity was observed along with extension twinning, contraction twinning significantly influenced the deformation, and such twins evolved into {10 $${\bar{1}}$$ 1}–{10 $${\bar{1}}$$ 2} double twins. Crystal plasticity simulation showed localized shear deformation within the contraction twins and double twins due to the enhanced activity of basal slip in the reoriented twin volume. Due to this, the twin–matrix interface was identified to be a potential crack initiation site. Thus, contraction twins were considered to have led to the failure of the material at a relatively low strain, suggesting that this deformation mode is detrimental to the cold formability of Mg and its alloys. With increasing temperature, there was a significant decrease in the activity of contraction twinning as well as extension twinning, along with a decrease in the tensile strength and an increase in the $${\varepsilon} _{\text {f}}$$ value. A combination of basal, prismatic, and pyramidal $$\langle {c+a}\rangle $$ slips accounted for a large percentage of the observed deformation activity at 423 K and 523 K. The lack of contraction twinning was explained by the expected decrease in the critical resolved shear stress values for pyramidal $$\langle {c+a}\rangle $$ slip, and the improved $${\varepsilon} _{\text {f}}$$ values at elevated temperatures were attributed to the vanishing activity of contraction twinning.

In this work the microstructure development during annealing of AZ31 sheets processed by equal channel angular pressing (ECAP) is presented. Samples with dimensions of 200 × 200 × 1.8 mm3 were processed in a single ECAP pass at 225 °C using a channel angle of 130°. Subsequent isothermal and isochronal heat treatments were used to reveal the microstructure stability of the ECAPed sheets at temperatures between 180 and 300 °C. A systematic analysis of the microstructure development was conducted using optical microscopy and electron backscatter diffraction (EBSD). It was found that a texture modification produced by the profuse activation of 10 1 - 2 extension twinning during ECAP is lost during annealing as a result of thermal detwinning. Moreover, a bimodal microstructure composed by small and coarse grains was observed at 250 °C and 300 °C as a result of the fast growth of a few grains. The reason for the selective grain growth is related with the activation of strain induced grain boundary migration which was stimulated by the large stored strain contained in the as-ECAP processed sheets. The dissolution of Mg17Al12 particles during annealing is also seen as a possible factor for the onset of rapid grain growth.

While cast magnesium components have been extensively used in the automotive industry, only niche applications are known to exist for magnesium sheets to this date. This is believed to originate from limitations in the material property spectrum covered by existing alloys. By utilising the twin-roll casting technique, novel Mg–Zn–Ca–Zr (ZXK) alloy sheets can be developed with improved formability as a result of a texture weakening effect. More importantly, it can be shown that these new alloy sheets can be processed at industrial scale. Based on the magnesium-specific design of a Volkswagen Passat decklid, the advantages of these new highly formable sheets in an automotive production environment can be evaluated.

The corrosion behaviours of commercial AZ91D alloy and Ca–Y-containing AZ91 alloy, fabricated by casting, were evaluated, and their microstructural changes and surface properties were analysed. The Ca–Y-containing AZ91 alloy showed superior corrosion resistance compared with the AZ91D alloy mainly because of the decrease in the Volta potential difference between the matrix and the secondary phases formed in the Ca–Y-containing alloy, such that micro-galvanic corrosion was significantly suppressed. Furthermore, passivity and stability of the surface film improved with the addition of Y to the AZ91 alloy. Thus, the overall corrosion resistance was significantly improved in the Ca–Y-containing AZ91 alloy.

Reducing vehicle weight and emissions by lightweight design is a major goal of the automotive industry. Magnesium as the lightest structural metal offers a significant weight saving potential compared to steel and aluminum. However, the poor formability of magnesium semi-finished products (e.g. sheets) has hindered the massive application of this metal. This poor formability arises due to the formation of strong textures. Typically the basal planes of the HCP-structure align parallel to the sheet plane. Such preferred orientation of the basal planes limits the ability of basal slip to accommodate plastic strain in the sheet plane and is thus unfavourable for ductility and formability of the sheets, especially at room temperature. A combination of new technologies could help to alleviate the strong textures formed in Mg sheets. In this regard the utilization of twin-roll casting (TRC) in combination with processing techniques which apply additional shear strain such as differential speed rolling (DSR) and/or equal channel angular pressing (ECAP) could refine the microstructure and modify the resulting deformation texture. In this study an AZ31 strip (3Al-1Zn-Mg Bal. wt.%) produced by TRC was hot rolled at 400 °C using a rolling speed of 10 m/min. A speed ratio of 10% between rolls was used. Rolled samples with dimensions of 200 x 200 x 1.8 mm receive a single pass of ECAP at 200 °C. After processing the microstructure of the samples were analyzed by means of optical microscopy, electron backscatter diffraction and X-ray diffraction. The results showed that the microstructure can be refined and the texture altered in comparison to conventionally rolled AZ31 sheets. The samples processed by ECAP show an increase in formability up to 50% higher than conventionally rolled sheets. This demonstrates the potential of using shear deformation for processing Mg sheets.

Magnesium as the lightest structural metal offers significant potential weight saving compared with steel and aluminium. Cast magnesium components are widely used, e.g. as engine blocks or gear box housings. To open more opportunities for weight saving, it is necessary to widen the application fields to wrought products, such as large thin walled components for which sheets as semi-finished products are needed. The production and processing of magnesium sheets material is currently hampered by the limited formability of magnesium and high costs. The use of the twin-roll casting (TRC) as a cost-effective manufacturing process and the development of new calcium-containing alloys are leading to a decisive reduction of those obstacles.

Innovative semi-finished products require tailoring mechanical properties and improving formability. Due to science-based alloy design as well as optimization of processing parameters (process-property relationship), it is now possible to control microstructures, phase distributions and texture development of magnesium sheets. A combination of new technologies and innovative alloys could help to alleviate the strong textures formed in semi-finished Mg products. The presentation will show Magnesium sheet development via twin roll casting technology and the how the subsequent warm rolling process influences the properties of the final magnesium sheet metal. Further optimisation of process parameters of twin roll casting and of the rolling process in combination with alloy design lead to a microstructure showing promising mechanical properties like high formability und high strength.

In the present work, the influence of the additions of zinc, zirconium and cerium-rich mischmetal on the microstructural recrystallization development of magnesium were investigated. Grain size and chemical composition were the principal variables of the billets used for indirect extrusion experiments. Significant changes in the evolution of the dynamic recrystallization (DRX) process as a function of the alloying element contents and the process variables were observed. Microstructures and preferred orientation of crystallites were correlated in order to discuss the role of alloy composition on the DRX. This discussion was based on the macro-texture measurements and some EBSD measurements of selected samples.

We examined the microstructure and texture evolution during the recrystallization annealing of cold rolled Mg-1Y and Mg-0.2Zn-1Y alloys. At the early annealing stage, new grains are nucleated on sub-units with 200–300 nm surrounded by dislocation walls within shear bands. The Zn and Y addition reduced the stacking fault energy which results in the high activity of non-basal deformation mechanisms and formation of segregation zones along the stacking faults. This causes the orientation of recrystallization nuclei to be effectively retained so that the texture weakens during the recrystallization without reducing the basal pole split into the sheet transverse direction.

Alloying modifications with Ca and Al of a binary Mg-1 wt.% Mn have been used to investigate the microstructure development during extrusion and the relation between these microstructures and the mechanical properties. Acoustic emission (AE) measurements were used to analyse dislocation or twin dominated deformation in differently textured fractions of the microstructure during tensile and compression testing. Ca appears to have a texture modifying effect and leads to the formation of unusual texture components with a tilt of basal planes out of the extrusion direction. This texture development has previously been described for rare earth containing magnesium alloys after extrusion. Al as an alloying element does not lead to the formation of such a component. Both elements have in common, that the alignment of basal plane normals perpendicular to the extrusion direction is reduced, having a substantial effect on the mechanical properties. Partially recrystallised microstructures obtained in Mg-1 wt.% Mn-0.3 wt.% Ca and Mg-1 wt.% Mn-1 wt.% Al after slow extrusion exhibit bimodal grain size distributions. Only in the case of Mg-1 wt.% Mn-8 wt.% Al a fully recrystallised microstructure is found, indicating differences in the grain nucleation rate during recrystallisation. In this alloy, the weakest texture and, correspondingly, the lowest asymmetry in mechanical properties was also observed.

The tension and compression deformation behavior of extruded magnesium-1 wt pct manganese alloys with nominally 0.3 wt pct (MN10) and 1 wt pct neodymium (MN11) was studied over the temperature range of 298 K to 523 K (25 °C to 250 °C). Nd additions to Mg alloys tend to reduce the strong basal texture exhibited by conventional wrought Mg alloys and this work was intended to study the effect of Nd on the deformation behavior of Mg alloys. Insitu tensile and compressive experiments were performed using a scanning electron microscopy, and electron backscatter diffraction was performed both before and after the deformation. A slip trace analysis technique was used to identify the distribution of the deformation systems as a function of strain, and based on this analysis and the texture of the undeformed samples, the critical resolved shear stress ratios between the deformation systems were estimated. In the case of MN11, the deformation behavior under tension at all temperatures was dominated by slip, while in compression, extension twinning was the major deformation mode. In tension at 323 K (50 °C), extension twinning, basal, prismatic 〈a〉, and pyramidal 〈c + a〉 slip were active in MN11. Much less extension twinning was observed at 423 K (150 °C), while basal slip and prismatic 〈a〉 slip were dominant and presented similar relative activities. At 523 K (250 °C), twinning was not observed, and basal slip controlled the deformation. With the reduction of Nd content, less slip deformation and more twinning were observed during the tensile deformation. However, like for MN11, the extent of twinning in MN10 decreased with increasing temperature and basal slip was the primary deformation mode at elevated temperatures. Extension twinning was the major deformation mode under compression for all test temperatures in MN10 and MN11. The tensile strength decreased with increasing temperature for both alloys, where MN10 was slightly stronger than MN11 at 323 K (50 °C), which was expected to be a result of the stronger basal texture exhibited by MN10 due to its lower Nd content. However, MN11 maintained its strength more at elevated temperatures compared with MN10, and this was explained to be a result of the greater Nd content.

The effect of process temperature on the microstructure and mechanical properties of Mg-3Al-1Zn sheets processed by ECAP is investigated in this work. A novel tool was developed for the implementation of ECAP to deform sheets with dimension of 200 mm × 200 mm × 1.8 mm. ECAP trials were performed successfully at three temperatures of 175, 200 and 225 oC using an internal channel angle of 130o. After the ECAP process, significant grain refinement and texture changes were observed in the ECAPed sheets. The tensile tests at room temperature showed that uniform elongation along the direction of ECAP process increases with the process temperature. The highest uniform strain was found at 17% using a processing temperature of 225 oC. The tensile uniform elongation at room temperature was improved by 31% in comparison with the as-received material.

The mechanical behavior of an extruded magnesium–manganese alloy containing 1 wt% of neodymium (MN11) has been investigated at temperatures ranging from room temperature to 400 °C at both quasi-static and dynamic rates. Conventional ex-situ tests, carried out in compression along the extrusion axis (EA), have been combined with in-situ tests in a scanning electron microscope (SEM) in order to elucidate the effect of a rare earth (RE) addition on the dominant deformation mechanisms. An unusually large activity of twinning was observed at room temperature in a wide range of quasi-static rates. Furthermore, the twinning activity has been found to increase at temperatures around 250 °C, where clear signs of dynamic strain aging (DSA) are also apparent. The enhanced twinning activity compared to conventional Mg alloys, not containing RE elements, is attributed to an increase in the critical resolved shear stress of basal slip (CRSS basal ) due to the presence of intermetallic RE-containing particles and to the Nd atoms in solid solution. The surprising decrease of the twinning activity at dynamic rates (∼10 3 s −1 ) may be explained by a decrease in the CRSS basal as the intermetallic RE-containg particles and the Nd solid solution strengthening become less effective with increasing strain rate.

The influence of the pre-compression level on subsequent tensile deformation behavior has been investigated for two extruded Mg alloys with a different grain size distribution. The Mg–Zn–R are earth alloy has homogeneous microstructure, while the Mg–Al–Zn alloy exhibits bimodal microstructure. Deformation tests were performed at room temperature and at a constant strain rate of 10−3 s−1. Three pre-compression stress levels were chosen to receive microstructure containing a low number of twins, partially and fully twinned grains, respectively. The concurrent acoustic emission (AE) measurement provides real time information about collective dislocation motion and twin nucleation. Active deformation mechanisms during tensile loading are discussed in term of the AE response.

Wrought magnesium (Mg) alloys are attractive for automotive applications where light-weighting is critical. One of the major challenges with conventional Mg alloys, such as Mg-3Al-1Zn(wt.%), is the strong texture formation after rolling and subsequent annealing, which results in anisotropic mechanical properties and poor cold formability [1]. It was observed that relatively weak texture can be obtained by dilute rare-earth additions such as Ce [2]. However, the mechanisms responsible for the weak texture formation during annealing are not clear. The goal of this study was to investigate recrystallization and texture evolution during annealing in a Ce containing Mg alloy system using in-situ techniques.

AZX310 alloy (Mg-3Al-1Zn-0.3Mn-0.5Ca in wt.%) sheets were produced via twin roll casting and subsequent warm rolling. The eutectic lamellae at the mid-thickness of the strip are changed during the rolling to fine spheroidal particles. The rolled sheets shows a large amount of fine Ca-rich particles which are homogeneously distributed through the whole sheet thickness. The AZX310 sheet shows excellent room temperature formability with the Erichsen index of 7.4, while the strength and ductility are maintained to the similar values of AZ31 sheets, i.e. tensile yield strength 189MPa, UTS 250 MPa and fracture strain 20%. The AZX310 sheet shows a relatively high corrosion resistance with the corrosion rate of 0.25mm / year, evaluated by neutral salt spray test at room temperature. The excellent mechanical performance of the AZX310 alloy sheet is related to the microstructure and texture. The high room temperature formability can be understood as a result of the texture randomization, while the relatively high strength and ductility of the AZX310 sheet is related to the existence of the fine Ca-rich particles.

The purpose of the present study is to elucidate the cause of a texture transition observed in hot-rolled Mg-Ce alloys, with increasing Ce content. More dilute compositions show a predominance of basal 〈a〉 dislocations, while the more concentrated alloys are shown to contain significant populations of 〈c+a〉 and non-basal 〈a〉 dislocations in the as-rolled and the recovery-annealed conditions. Like Mg-Nd, the grain size in Mg-Ce decreases with increasing Ce. Unlike Mg-Nd, the second-phase particles observed are of the equilibrium phase, and the equilibrium solid solubility at the hot working temperature corresponds to the composition above which weak textures form. The significances of both non-basal slip and Zener pinning as contributors to texture randomization are discussed.

Hot-rolled, binary Mg-Nd alloys with compositions ≥0.095 at. pct undergo the texture weakening phenomenon that has been reported in a number of Mg–rare earth (RE) alloys. However, alloys with compositions ≤0.01 at. pct retain a strong basal texture typical of pure Mg and other Mg alloys. Measurements of intragranular misorientation axes obtained using electron backscatter diffraction (EBSD) show that more dilute alloys contain predominantly basal $$ $$ dislocations, while richer alloys contain primarily prismatic $$ $$ dislocations. It is suggested that this change in dislocation content is related to a change in the dynamic recrystallization (DRX) mechanism. Metastable second-phase Mg x Nd1–x intermetallic particles are present within the alloys, and an annealing study indicates that the alloys undergoing texture weakening have grain sizes well predicted by classical Zener drag theory. Even though the more dilute alloys also contain second-phase particles, they are not sufficient to induce pinning. The promotion of nonbasal slip and the reduction in grain boundary mobility due to Zener drag are suggested as controlling mechanisms that promote the observed texture weakening phenomena.

Microstructural evolution during the annealing of cold rolled Mg, Mg-1.5Nd and Mg-3Y sheets has been examined. The experimental results show a significant difference in recrystallization kinetics and grain growth between pure Mg and Mg-RE alloy sheets. Pure Mg sheet shows rapid recrystallization and grain growth, whereas recrystallization is considerably retarded in the Mg-RE alloys. Although recrystallized grains which are triggered at shear bands in the cold rolled pure Mg sheet show a relatively weak texture with a basal pole split into the sheet rolling direction, rapid grain growth is accompanied by re-strengthening of the basal-type texture. In contrast, a weak texture appears in the early recrystallization stage in Mg-RE alloys and is retained during annealing due to retarded recrystallization and grain growth.

The high strain rate behaviour of magnesium alloys is of great interest to automotive,aerospace and/or defence industries because some critical components should have the propermechanical properties to work under crash or impact conditions. In the current study, resultsfrom an extensive experimental program are presented. The uniaxial mechanical behaviour ofAZ31 sheet under dynamic conditions (ε=103 s-1) is analyzed and compared with that observedat low strain rates. AZ31 sheets have been tested in tension and compression using Hopkinsonbar apparatus at 25°C and 250°C. Moreover, interrupted tests were also performed in orderto relate the evolution of deformation mechanisms with strain. Finally, detailed microstructureand texture examination by electron backscatter di raction (EBSD) and neutron di ractionhas been carried out in order to elucidate the predominant deformation and recrystallizationmechanisms.

Although conventional Mg alloys develop strong crystallographic textures during deformation that persist during annealing, the addition of rare earth (RE) elements can induce comparably weaker textures. The texture weakening effect is explored using hot-rolled Mg-Y alloys of a single phase to focus on the possibility of solute effects. Of the studied compositions, the richer alloys (≥0.17 at. pct) show the weakening effect, whereas the most dilute alloy (≤0.03 at. pct) does not. Electron backscattered diffraction (EBSD) analysis of intragranular misorientation axes (IGMA) indicate that the geometrically necessary dislocation (GND) content in dilute, hot-rolled alloys contain primarily basal 〈a〉 dislocations. At higher concentrations, the dislocations are predominantly prismatic 〈a〉 type. This change in the GND content suggests a change in dynamic recrystallization (DRX) mode. For example, nonbasal cross slip has been associated with continuous DRX. Furthermore, nonbasal slip might also promote more homogenous shear banding/twinning. Both of these mechanisms have been shown previously to give rise to more randomly oriented nuclei during DRX. Energy dispersive X-ray spectroscopy performed through transmission electron microscopy shows that Mg-Y exhibits significant grain boundary solute segregation, consistent with recent observations of solute clustering. Slow grain growth may be explained by solute drag. It is hypothesized that limited grain boundary mobility suppresses conventional discontinuous DRX, which has been shown to retain the deformation texture. The promotion of nonbasal slip and suppression of grain boundary mobility are proposed as solid solution-based mechanisms responsible for the observed texture weakening phenomenon in Mg rare earth alloys.

Ambient temperature compression tests with concurrent acoustic emission (AE) measurements have been performed on a hydrostatically extruded, fine-grained, round bar of alloy AZ31 parallel to the extrusion axis. A multiple increase in the AE count rates to peak intensities was detected with increasing strain. An analysis of the samples tested to specific values of strain using electron backscattering diffraction revealed that (10–12) twins first appear in large grains and that only with increasing strain do smaller grains tend to twin.

The influence of crystallographic texture on high cycle fatigue behaviour has been studied using an extruded rectangular profile of the AZ31 (Mg-Al-3wt%-Zn-wt1%) alloy. The fatigue samples, cut at 0, 45 and 90° to the extrusion direction correspond to different initial textures. Besides high cycle fatigue tests, quasi-static tensile and compression tests were performed to assess the tension-compression asymmetries as a function of the initial texture. The micro-mechanisms of fatigue crack initiation were investigated using scanning electron microscopy and electron backscatter diffraction. Differences in the mechanical properties and the endurance limit for the different sample directions are related to the initial texture and, subsequently, the easiness or difficulty of slip/twinning.

Single additions of the rare earth (RE) elements cerium, yttrium or neodymium have been made to magnesium–manganese alloys in order to investigate their influence on the microstructure and texture formed during indirect extrusion and the resulting mechanical properties. Whereas the binary Mg–Mn alloy M1 exhibits a 〈10.0〉 or 〈10.0〉–〈11.0〉 fibre texture depending on the extrusion rate, the RE-containing alloys exhibit weaker recrystallisation textures and the formation of a new texture component. The preferential growth of grains having 〈11.0〉 parallel to the extrusion direction was hindered in these alloys. For the rare earth elements used in this work it appears that Nd is a much stronger texture modifier compared to Ce or Y in Mg–Mn alloys. The weaker texture leads to increased ductility, lower yield and ultimate stresses, but a decrease in the asymmetric yield behaviour of the extruded bars.

Microstructural evolution during the annealing of AZ31 extruded rod at 400 °C has been examined by employing neutron diffraction and electron backscatter diffraction (EBSD). In the as-extruded bar, equiaxed grains smaller than 5 μm and large elongated grains having significant degrees of internal misorientation are oriented mainly with 1 0 1 ¯ 0 > parallel to the extrusion direction. Rapid grain growth occurs within the 180 s annealing period at 400 °C at the expense of the small grains with the internal orientation gradient as driving force. After short time annealing, small equiaxed grains are formed inside the large elongated grains, and grains having 1 1 2 ¯ 0 > parallel to the extrusion direction show preferred growth. As a result, a transition of the main texture component to the 1 1 2 ¯ 0 > component occurs after annealing for 1800 s at 400 °C.

The influence of the initial microstructure on the deep drawability and the associated microstructural evolution in two different magnesium alloy sheets, AZ31 and ZE10, has been examined. Tensile testing at room temperature shows that the AZ31 sheet has high plastic strain ratios, r = 2–3, which are caused by strong basal-type texture. The ZE10 sheet shows lower r values, r ∼ 1, as a result of its weak texture. Deep drawing experiments carried out over the temperature range 100–300 °C revealed that the ZE10 sheet can be successfully deep-drawn at lower temperatures than the AZ31 sheet. The ZE10 cups show earing despite the weak texture and low normal anisotropy, while earing of the AZ31 cups is negligible. In the ZE10 cups, deformation is accommodated mainly by 〈a〉 slips and by compression as well as secondary twinning. The occurrence of dynamic recrystallization is observed in successfully deep-drawn AZ31 cups.

The influences of rare earth elements addition on the crystallographic texture and microstructural evolutions are examined during rolling and annealing of Mg-sheets. In case of Nd or Y additions, dynamic recrystallisation is suppressed such that the deformed microstructure is observed after hot rolling with relatively large strain per pass. Cold rolled binary Mg-Nd alloy sheet shows strong texture with splitting of the basal poles in the rolling direction, however, the texture intensity decreases significantly during the recrystallisation annealing. From the comparison of deep drawing behaviours between commercial ZE10 and AZ31 sheets, it is observed that the addition of the rare earth elements and accompanying texture changes result in the improved formability.

The influence of crystallographic texture on the mechanical properties of magnesium alloys is already well-known. However, it is not clear how the crystallographic texture affects the fatigue properties in the sense of cyclic deformation behaviour of magnesium alloys. The objective of this study is to investigate and compare the deformation processes of the extruded magnesium alloys AZ31 and AZ80 during static and cyclic tensile testing. The influence of the loading condition and chemical composition on the evolution of the microstructure and the crystallographic texture has been observed. Changes of the plastic strain have been observed and have been interpreted for both AZ alloys with cyclic hardening curves. However, the maximal stress during the fatigue test was higher than the TYS for both alloys. Both experimental materials exhibited significant lower plastic deformations and lower density of tensile twins compared to static tensile test. The microstructure and texture analyses have been performed before and after experiments.

The contribution of twinning to the evolution of texture and microstructure during hot rolling of pure magnesium was investigated using 2-dimensional and 3-dimensional EBSD-based orientation microscopy. A very sharp 〈0 0 0 1〉 fibre texture component parallel to the sheet normal direction is observed after hot rolling, independent of the rolling degree. Tensile twins are observed in case that the c-axis of the matrix grains are inclined to the sheet normal direction by an angle larger than 45°. Compression twins, on the other hand, are found in grains whose c-axis is inclined to the normal direction by less than 30°. The formation of secondary twins is observed in most compression twins. At the intersection of two secondary twins new grains are formed provided that the matrix and twins have a common crystallographic rotation axis. These new grains have a specific orientation relation to the matrix grains, characterized by a rotation about an axis close to the c-axis. The newly formed grains grow effectively during the subsequent annealing. An estimation of their frequency shows that they may contribute every third to second grain in the recrystallised microstructure. Consequently, these new grains contribute to the persistence of strong basal texture of rolled sheet.

The magnesium alloys AZ80 und ZK60 received from Dead Sea Magnesium in as-cast conditions were extruded at T = 350 °C using an extrusion ratio of ER = 22. The extruded bars were severely plastically deformed by equal channel angular pressing (ECAP). Multiple ECAP processing up to 8 passes was done. The ECAP-induced changes in grain size and grain size distribution were measured by transmission electron microscopy while changes in dislocation density and crystallographic textures were determined by positron annihilation spectroscopy and X-ray diffraction analysis, respectively. The strain induced by ECAP was found to influence the microstructural characteristics, in particular the grain size, the dislocation density, and the crystallographic texture, which in turn enhance (or deteriorate) the mechanical or fatigue response of both alloys.

The microstructure evolution during high pressure torsion and its influence on the mechanical properties of AZ80 magnesium alloy is presented in this study. Significant grain refinement was observed after high pressure torsion, while the homogeneity of the grain structure increases with the number of revolutions. Grain size decreases to about 50 nm after 15 revolutions. The microhardness profiles measured at through-thickness and through-width directions show no significant variation at different positions of the sample. Moreover, the negligible effect of the revolution number on the microhardness value was observed.

Two extruded magnesium alloys, AZ31 with a bimodal microstructure and ZE10 with a homogeneous microstructure, were pre-compressed and subsequently subjected to tensile loading. The acoustic emission (AE) technique was concurrently applied to determine the activity of particular deformation mechanisms. Significant changes in the AE response were correlated with the inflection points on the tensile curve. Twinning and detwinning processes were analyzed using the AE dataset. Particularly, nucleation of various types of twins and the influence of twins produced by pre-straining on the subsequent hardening behavior were investigated in detail. The output of the AE analysis was related to microstructure observations provided by the electron backscattered diffraction (EBSD) method.

The wrought magnesium alloys AZ80 and ZK60 were extruded at 175°C ≤ T ≤ 350°C at an extrusion ratio of ER = 12. With decreasing extrusion temperatures a marked refinement in grain size was found for both alloys resulting in higher values of yield stress while UTS values were hardly affected. As opposed to AZ80, a marked yield stress differential between loading in tension and compression was observed in ZK60, this effect being explained by the differences in crystallographic texture.

The deformation degrees in near-surface zones and related microstructural changes in CuZn30 were determined after shot peening and ball-burnishing. The induced depths of plastic deformation increase with Almen intensity and rolling pressure in shot peening and ball-burnishing, respectively. As the ball size in burnishing increases, the depth of plastic deformation also increases. The local degrees of cold work within the affected depths were estimated by comparing micro-hardness values, penetration depths of induced slip bands as well as X-ray diffraction peak widths with those measured in blanks cold rolled to fixed degrees of plastic strain. The results clearly indicate that very high local deformation degrees above 80% are typically induced by mechanical surface treatments in areas very close to the surface with this deformation degree gradually decreasing with increasing distance to the surface. Depending on the intensity of ball-burnishing, deformation degrees still of the order of 10% were observed in regions having distances to the surface of as large as 1000 (m.

The anisotropic mechanical behavior of extruded AZ31 magnesium alloy is described in relation to the crystallographic texture. Specimens taken at 0°, 45° and 90° to the extrusion direction were uniaxially loaded in tension and compression, and the texture evolution was measured under load, using synchrotron radiation. The correlation between the initial texture, the mechanical anisotropy and the activation of different deformation modes was interpreted using the in situ texture measurements and viscoplastic self-consistent simulation results. The activity of the basal 〈 a 〉 slip and the tensile twinning exert a significant effect on the mechanical anisotropy during tension, while the importance of the 〈 c + a 〉 slip increases during compression.

The crystallographic response to deformation – texture evolution, internal elastic strain, and twin evolution – was measured for three load/orientation variants for AZ31 magnesium alloy extrudate tested in-situ in a synchrotron beamline. Specimens were loaded in tension parallel to the extrudate transverse direction, in compression along the same axis, and in compression parallel to the extrudate normal direction. The crystallographic responses are correlated with the mechanical behaviour of the extrudate.

The texture influence on the mechanical behavior during uniaxial tension was studied in AZ31 (Mg – 3 Al – 1 Zn in wt.%), one of the common wrought Mg alloys. Since three tensile samples were cut in 0°, 45°, 90° to the extrusion direction, the initial bar texture influences on the mechanical behavior differently. In-situ texture measurements were carried out using hard X-rays under loading condition. According to the initial texture loading results in a variation of the mechanical behavior (yield strength, ultimate tensile strength and strain hardening rate) and in different final textures. The different texture development in each sample relates directly to the activation of different deformation systems, which is strongly influenced by the initial texture

Twin-roll casting of magnesium alloys is seen as a promising processing route to enable a further development of sheet properties. In this regard the influence of melt temperature and rolling speed on the microstructure and texture development of magnesium strips is investigated for alloy AZ31. Microstructure and through-thickness texture measurements are used to reveal effects of grain growth during solidification and deformation of the strip. For this purpose synchrotron radiation at the PETRA III storage ring of DESY in Germany has been used. Twin-roll casting with varied processing parameters leads to microstructures ranging from directionally solidified grains to deformed microstructures with a profound fraction of recrystallized grains. Specifically, sheets rolled from different strips exhibit an alignment of their Mg basal planes in the sheet plane with certain significance depending on grain size and grain orientation effects.

The texture development during isochronal annealing at 250, 300 and 350 °C for 30 min of a hot rolled Mg AZ31 sheet produced by twin-roll casting was studied in this work. It was found that the rolling texture shows some features that resemble the textures that develop in rolled Mg alloys with rare earth additions. During further heat treatment, special attention was given to the deformation and recrystallization mechanisms, and grain growth that control the texture development. It was found that at 250 and 300 °C extended recovery and discontinuous recrystallization influence the texture by generating strain free grains with off-basal orientation. Conversely, during annealing at 350 °C growth of grains with their c-axis close to the (0 0 0 1) leads to the formation of the well-known basal type texture.

Tensile testing of hydrostatically extruded round bars of AZ31 and AZ61 has been performed to analyse the flow behaviour as well as the microstructure and texture development as a function of temperature (175–225 °C) and strain rate (0.0001–0.01 s−1). The post-testing microstructure is a result of dynamic recrystallization with varying significance of different texture components. In some cases the resulting textures are found to be similar to those textures that typically develop during extrusion of rare-earth-containing magnesium alloys. Dynamic recrystallization (DRX) and grain boundary sliding (GBS) are considered as the mechanisms that generate the changes in texture. Precipitates can exert a grain boundary pinning effect limiting grain growth. These different mechanisms contribute differently to the texture development if the testing parameters are changed.

An AZ31 rolled sheet alloy has been tested at dynamic strain rates ( e ˙ ∼ 10 3 s − 1 ) at 250 °C up to various intermediate strains before failure in order to investigate the predominant deformation and restoration mechanisms. In particular, tests have been carried out in compression along the rolling direction (RD), in tension along the RD and in compression along the normal direction (ND). It has been found that dynamic recrystallization (DRX) takes place despite the limited diffusion taking place under the high strain rates investigated. The DRX mechanisms and kinetics depend on the operative deformation mechanisms and thus vary for different loading modes (tension, compression) as well as for different relative orientations between the loading axis and the c-axes of the grains. In particular, DRX is enhanced by the operation of 〈c + a〉 slip, since cross-slip and climb take place more readily than for other slip systems, and thus the formation of high angle boundaries is easier. DRX is also clearly promoted by twinning.

In this work, the superplastic behavior of AZ31, AZ61 and AZ80 magnesium alloys was investigated. The alloys were hydrostatically extruded at only 150 °C to get fine grained microstructures (−2, 10−3and 10−4s−1. It was found that all alloys exhibited superplasticity at 200 °C, 175 °C and 225 °C for AZ31, AZ61 and AZ80 alloys, respectively. Low temperature dynamic recrystallisation played an important role for generating a finer and homogeneous microstructure during testing which enhances the deformation behavior of the alloys at these temperatures.

The role of rare earth addition on the microstructure and texture during recrystallization of cold rolled sheets is investigated by a comparative study of pure Mg, Mg-3Y and Mg1.5Nd sheets. In pure Mg, nucleation occurs mainly at shear bands which results in a texture weakening. The basal-type texture re-strengthens rapidly during grain growth of the pure Mg sheet. In contrast, in the Mg-RE alloys the weaker texture formed during early recrystallization strage is retained during further annealing due to retarded grain growth. Uni-axial tensile and Erichsen tests show that ductility and sheet formability are significantly improved by addition of rare earth elements.

The microstructural evolution of an AZ31 rolled sheet during dynamic deformation at strain rates of ∼103 s−1 has been investigated by electron backscatter diffraction, X-ray and neutron diffraction. The influence of orientation on the predominant deformation mechanisms and on the recovery processes taking place during deformation has been systematically examined. The results have been compared with those corresponding to the same alloy tested quasi-statically under equivalent conditions. It has been found that strain rate enhances the activation of { 1 0 1 ¯ 2 } extension twinning dramatically, while contraction and secondary twinning are not significantly influenced. The polarity of { 1 0 1 ¯ 2 } extension twinning is even reversed in some grains under selected testing conditions. Significant grain subdivision by the formation of geometrically necessary boundaries (GNBs) takes place during both quasi-static and dynamic deformation of this AZ31 alloy. It is remarkable that GNBs of high misorientations form even at the highest strain rates. The phenomenon of recovery has been found to be orientation dependent.

Commercial magnesium alloys such as AZ31 exhibit strong crystallographic textures during massive deformation such as rolling. A randomisation of the texture, however, was found in alloys with rare earth (RE) elements in solid solution. This paper describes the development of microstructure and texture during rolling of the Al-free RE-containing wrought magnesium alloy ZEK100 during hot rolling. This alloy develops a strong texture with a pronounced component towards the transverse direction (TD) of the sheets. This TD component forms already after the first rolling pass, persists through all following passes and is further enhanced by subsequent heat treatment. These results are contrasted with results from a study on texture development of binary RE containing Mg-alloys, which show that the presence of RE elements alone is not responsible for the tilt of basal planes towards the TD. There is, however, a threshold concentration at which the texture begins to weaken.

The influence of crystallographic texture on fatigue failure mechanisms was studied by comparing the fatigue behaviour of two extruded magnesium alloys, AZ31 and ZN11. The microstructures and fracture surfaces of specimens were examined using scanning electron microscopy (SEM) to reveal the micromechanisms of fatigue crack initiation. The AZ31 alloy has an inhomogeneous grain structure and strong fibre texture, which cause strong asymmetry in the tensile and compressive yield strengths. This yield stress asymmetry is related to the high twinning activity under compressive loading. The metallographic investigation reveals that the cracks are mainly initiated at twin boundaries. On the other hand, a weak texture and fully recrystallised, homogeneous grain structure are found in the experimental alloy ZN11 after extrusion. As a consequence, twinning is suppressed and no yield stress asymmetry is observed. The fatigue failure of ZN11 is initiated by cyclic slip deformation.

Wrought magnesium alloy AZ31 was pre-compressed and subsequently subjected to tensile loading. Due to a strong fibre texture of the alloy the level of pre-compression stress significantly influences the following tensile test. The results of acoustic emission (AE) measurement are correlated with the stress-time curves and differences in the AE count rate were used to reveal changes in underlying deformation mechanisms. First, the compression-tension test was recorded by using the AE technique and then the test was repeated to specific points on the deformation curve, where the AE count rate exhibits strong changes in its activity. A pronounced S-shape of the tensile curve and AE peaks were observed. It highlights the role of detwinning and the nucleation of new twins during the tensile test. The subsequent analysis of microstructure using electron back scattered diffraction (EBSD) method opens a detailed insight into microstructural changes.