Search

AZ61 and AM60 magnesium alloys, with higher mechanical strengths than that of the most commonly used AZ31 alloy, were subjected to high-temperature rolling. Although the basal textures of the as-rolled sheets of both alloys were significantly weakened by annealing, the texture weakening was more significant in the latter than in the former. In addition, splitting of the basal pole was not retained after annealing for the AZ61 alloy, but this type of texture was preserved in the case of the AM60 alloy. The formation of statically recrystallized grains with dispersed orientations resulted in the aforementioned change in texture. The difference in the static recrystallization behavior could be attributed to the solute effect of zinc atoms. The annealed AZ61 and AM60 alloy sheets exhibited excellent stretch formability at room temperature, with Erichsen values of 7.8 and 8.5 mm, respectively, comparable to those of aluminum alloys. The higher Erichsen value for the AM60 alloy compared to that of the AZ61 alloy resulted from the more weakened basal texture and the splitting of the basal pole with an inclination angle of ±20° in the rolling direction, which are favorable for basal slip during sheet forming. [ABSTRACT FROM AUTHOR]

The fabrication of magnesium (Mg) alloy sheets with both high mechanical strength and superior cold formability was sought by optimizing the aluminum (Al) content of the alloy sheets. We investigated the influence of varying Al content from 3 wt% to 8 wt% on the texture, mechanical properties, and stretch formability of AM series Mg alloys, processed by high-temperature rolling. The ultimate tensile strength improved steadily from 247 MPa to 303 MPa with an increase in Al, due to solid solution strengthening. The basal texture intensity decreased with increasing Al content, reached a minimum value at 6 wt% Al, and then increased as more Al was added. The weakest basal texture led to the smallest Lankford value and the largest strain hardening exponent in the AM60 (6 wt% Al) alloy. The alloys with lower Al contents of 3–5 wt% exhibited a high fracture elongation of 27%, which continuously decreased to 23% as the Al content increased to 8 wt%. The AM50 alloy exhibited excellent stretch formability with the largest Erichsen value of 9.1, while the AM30 and AM80 alloys showed much smaller Erichsen values of 5.6 and 6.0, respectively. This can be attributed to a good balance among the decreased r -value, increased n -value, and enhanced tensile ductility in the AM50 alloy, despite its basal texture being slightly stronger than that of the AM60 alloy. [ABSTRACT FROM AUTHOR]

Abstract: Mg–3Al–1Zn magnesium alloy sheets rolled at 350°C, 450°C and 525°C, which exhibit approximately the same grain size but a significant decrease in basal texture intensity with increasing rolling temperature, were used for investigating the influence of initial texture on deep drawing behaviour at room temperature. The sheets rolled at 350°C and 450°C fracture at drawing ratios of 1.5 and 1.7, respectively, while the sheet rolled at 525°C can be successfully drawn at a large drawing ratio of 1.8. The fracture site changes from the shoulder of drawn cup to the edge of the flange with the weakening of initial basal texture. At the flange, the basal texture dramatically changes to the TD-texture with basal planes perpendicular to the sheet plane accompanied with sheet thickening. Both tensile twinning and basal slip contribute to this texture change due to compressive stress along the circumferential direction. In the case of weak initial texture, relatively restricted tensile twinning and more activated basal slip delay the development of the TD-texture, which is favoured for maintaining deformation capability at the flange and in turn enhances deep drawability. The deformation behaviour is discussed in terms of the change in Schmid factor for basal slip during deep drawing. [Copyright &y& Elsevier]

Abstract: The Mg–3Al–1Zn magnesium alloy sheets rolled at 573 and 798K characterized by strong and weak basal textures, respectively, were further subjected by a single high temperature rolling pass at 798K. The sheet rolled only at 798K throughout rolling exhibits a double peak texture in both of as-rolled and annealed conditions. By contrast, for the sheet rolled at 573 and 798K, the reduction rate of basal texture intensity is larger and the single peak of the rolling texture changes to the double peak with basal poles largely tilting in the RD at ∼20° after annealing, which is rarely observed in wrought magnesium alloys. This phenomenon is resulted from static recrystallization and may be related to enhanced pyramidal 〈c+a〉 slip during high temperature rolling due to the initial strong basal texture. [Copyright &y& Elsevier]

Poor formability of rolled magnesium (Mg) alloys extremely restricts applications in form of sheets originating from formation of strong basal texture. Recently, we found that increasing rolling temperature from 723 to 798 K for a AZ31 Mg alloy can significantly improve stretch formability due to remarkable texture weakening after annealing. In this study, static recrystallization behaviors of AZ31 alloy sheets rolled at 723 and 798 K were investigated by electron backscattered diffraction analyses at different annealing stages in order to understand the origin of high temperature rolling on texture weakening. For both sheets, similar deformation microstructures with approximately the same types and fractions of twins exist in the as-rolled condition and recrystallized grains are mainly formed at pre-existing grain boundaries due to discontinuous recrystallization during subsequent annealing. However, only the basal texture of the latter remarkably weakens due to the formation of new recrystallized grains with well-dispersed orientations. Non-basal slips enhanced during high temperature rolling at 798 K are most likely responsible for the texture randomization as a result of rotations of recrystallization nuclei. [ABSTRACT FROM AUTHOR]

Abstract: The microstructural and textural evolution during post-annealing as well as mechanical properties of a Mg–4Y–3RE magnesium alloy sheet processed by differential speed rolling at 823K were investigated. The as-rolled sheet exhibits deformation microstructure regardless of the high rolling temperature. Static recrystallization occurs around second-phase particles as a result of particle-stimulated nucleation and also at pre-existing grain boundaries due to solute effects of rare-earth elements, resulting in randomization of basal texture. Despite a large amount of second-phase particles, the weakened texture leads to a moderate stretch formability with an Erichsen value of 4.4. [Copyright &y& Elsevier]

Abstract: The recrystallization and grain growth behaviour of Mg–3Al–1Zn alloy sheets with a deformation microstructure, obtained by a combination of high-temperature rolling and subsequent warm rolling, was investigated at different stages of annealing. The basal texture was significantly weakened as a result of the formation of new grains with a largely altered c-axis orientation relative to the initial basal orientation owing to discontinuous static recrystallization during primary recrystallization. The new grains nucleated mostly at the pre-existing grain boundaries rather than at the intersections of twins or within the twins. Subsequent grain growth led to further progression of the texture weakening accompanied by an enhancement in the basal pole inclination. [Copyright &y& Elsevier]

Differential speed rolling (DSR) was carried out on commercial pure titanium at rolling temperatures from room temperature to 773K. The basal texture appears when the rolling temperature is higher than 573K and it lacks stability during annealing. Originating from texture effects, the DSRed sheet exhibits a larger Lankford value and a smaller planar anisotropy, which lead to a remarkable improvement in stretch formability regardless of a decrease in tensile elongation compared with symmetrically rolled sheet. [Copyright &y& Elsevier]

The Mg–3Al–1Zn magnesium alloy sheets with initial extrusion and casting microstructures were symmetrically rolled at a high temperature of 823K, followed by a warm rolling at 498K. The initial texture plays a vital role in texture development and results in inclination angle of split basal pole varying from ±15° to ±40°. The sheet rolled perpendicular to extrusion direction exhibits a homogeneous microstructure with an inclination angle of ±25° and the highest Erichsen value of 9.7. [Copyright &y& Elsevier]

Abstract: The microstructural and textural evolution of the hot-extruded AZ31 alloy plate during differential speed rolling (DSR) has been investigated. For the hot-extruded plate, a large texture gradient exists in the thickness direction while the grain size distribution is nearly homogenous. The textural evolutions at near-surface and mid-layer regions are different between the DSR processed and the normal symmetric rolled sheets. The inclination of basal pole at the mid-layer increases at an accelerating rate with progress of the DSR processing due to the enhancement of the unidirectional shear bands. The deformation tends to concentrate on the previously formed shear bands, which exhibit a favored crystalline orientation for further shear localization. [Copyright &y& Elsevier]

The influence of reduction per pass over the range of 9–63% on the microstructure and texture of Mg–3Al–1Zn magnesium alloy sheets processed by differential speed rolling at the same total reduction of 63% have been investigated. With increasing reduction per pass, the number of unidirectional shear bands increases, resulting in a more homogeneous microstructure and a weaker basal texture at mid-layer. The inclination direction of the basal pole with respect to the rolling direction depends on the reduction per pass. [Copyright &y& Elsevier]

Abstract: A heat-treatable AZ80 magnesium alloy has been subjected to differential speed rolling (DSR) at a large thickness reduction per pass of 33%, and microstructure, texture, mechanical properties, stretch formability as well as texture evolution during stretch forming have been investigated. The basal pole of the DSR-processed sheet tilts toward the rolling direction at 15°. The as-rolled sheet exhibits a combination of high strength (tensile strength: 329MPa) and high ductility (fracture elongation: 25%). The Erichsen value at room temperature improves from 3.7 to 4.5 compared with the normal-rolled sheet. The enhancement of the stretch formability can be attributed to the texture effects due to the same grain size of 7μm. The DSR-processed sheet exhibits a larger Schmid factor for basal slip and the inclination of basal pole retains during the stretch forming. The aging treatment remarkably enhances the mechanical strength further while it significantly deteriorates the formability. [Copyright &y& Elsevier]

Mg–6Al–1Zn magnesium alloy sheets were rolled at high temperatures of 723–793K using differential speed rolling. The Erichsen value remarkably increases about 1.5 times due to the weakened basal texture regardless of the coarser grains with increasing the rolling temperature from 723 to 793K. The sheet rolled at 793K exhibits a combination of a superior stretch formability with an Erichsen value of 7.0 and a high tensile strength of 300MPa at room temperature. [Copyright &y& Elsevier]