Mg sheet: the effect of process parameters and alloy composition on texture and mechanical properties

Abstract

The paper addresses the relationship between microstructure, texture, and mechanical properties of rolled magnesium sheets. The effect of rolling temperature and alloying elements on texture development and mechanical properties is demonstrated. Special focus is paid to the potential of rare earth elements to modify the anisotropic behavior and to weaken the strong basal texture of magnesium sheets. Alloy design that considers these possibilities together with appropriate selection of process parameters show the road to magnesium sheets with improved forming properties. intRoduCtionThe use of sheet material as a semifi nished product enables a wide scope for design. The development of new materials such as magnesium alloys for lightweight application requires the development of semi-fi nished products for an expansion of possible applications. Magnesium sheet offers a signifi cant possibility of producing components in a large variety of shapes from its simple fl at structure. However, despite their great potential wrought magnesium alloys have hitherto only played a small role in lightweight structural applications. A major technical reason is the fact that commercial magnesium sheets like AZ31 are limited in their ductility and formability, especially at room temperature. This is related to the occurrence of magnesium with a hexagonalclose-packed lattice structure. In consequence, there are a small number of deformation mechanisms that can be activated during plastic deformation at room temperature compared to metals with cubic lattice structures. Basal slip and so-called tensile twinning are

Effect of Rare-Earth Additions on the Texture of Wrought Magnesium Alloys: The Role of Grain Boundary Segregation

“…[8] Work on dilute binary Mg-RE alloys revealed that a texture change could be obtained in Mg-RE alloys even when the level of solute addition was below the solubility limit. [3,4,8] The potency of different individual RE elements was also studied. It was shown that the rare-earth effect can be achieved at very low levels of addition, for example only 0.04 at.…”

“…pct Ce was observed to also produce a strong texture weakening effect. [4] One remarkable characteristic of the RE effect is that so little addition (e.g., less than 1 in 3000 atoms for Mg-Ce) is needed to produce such a potent change in texture. This observation led to the suggestion that segregation is likely to be important in enabling much higher concentrations than added in the bulk to be achieved locally.…”

“…Reducing the texture strength or changing the texture is therefore one route to improving formability. [2][3][4] This can be achieved by changing the processing route; for example, equal channel angular extrusion, shear rolling, or other novel metal forming methods have been successfully used to alter the texture in magnesium and provide improvements in ductility. [5,6] However, alloying is also another attractive route to changing texture.…”

Microstructure, Texture and Mechanical Properties of Mg-Zn-Ce Alloy Extruded at Different Temperatures

“…As described in the previous paragraph, Stanford and Barnett 16) reported that the RE texture component detected in a Mg-Gd alloy extruded at around 723 K originated from the shear bands in the unrecrystallized grains. Some researchers 13,15) support the findings of Stanford and Barnett, where shear bands are regarded as the nucleation site of grains composing random and/or TD-split textures in a rolled Mg alloy. However, in our results, the RE texture component did not appear in the as-extruded (at 573 K) specimen, in which a lot of shear bands were detected.…”

“…4,5) The addition of minor special elements causes not only a reduction in the intensity of the basal plane texture but also spreading of the basal poles toward the transverse direction (TD). [5][6][7][8][9][10][11][12][13][14][15] The unique texture such as ''rare earth (RE)'' texture component, 16) corresponding to the h11 2 21i direction parallel to the extrusion direction (ED), is obtained during extruding of Mg-Mn-RE and Mg-RE alloys. [16][17][18][19][20][21][22][23] Recently, Luo et al 24) reported that the RE texture component also appears in an extruded Mg-Zn-Ce alloy, and it exhibits a good balance of tensile yield stress and ductility compared with an extruded Mg-Ce alloy.…”