Processing Effects on the Formability of Magnesium Alloy Sheets

Abstract

Abstract:As a generalized semi-finished product, the use of magnesium sheets requires addressing two major aspects of their processing: their microstructure and texture control, which are both essential for the forming behavior of such sheets during their forming to parts. Further, the processing of such sheets is complex, and therefore expensive, and requires simplification. In this work, magnesium alloys AZ31, ZE10, and ME21 are investigated in the form of conventionally rolled sheets, as well as in the form of extruded sheets. Their microstructural and textural development are correlated to their mechanical and forming properties. During extrusion, strong textures develop that hinder stretch-forming operations, even in rare earth-containing alloys. Chemical composition and process parameters have a significant impact on the texture development, and enable the design of sheet materials with weak textures and potentially enhanced formability.

Processing Effects on the Formability of Extruded Flat Products of Magnesium Alloys

“…The variation of the intensities is small. This texture results are typical for AZ31 and compare well to those of rolled or extruded sheets of this alloy (Styczynski et al, 2004;Yi et al, 2006;Victoria-Hernandez et al, 2014;Bohlen et al, 2018a).…”

“…Accommodation of such strain may require the same orientation considerations as above, but they are especially needed homogeneously in all in-plane directions. Although sample dimensions in this study did not allow revealing the mechanical behavior along the transverse direction, it has been shown in earlier work on extruded sheets that a strong anisotropy of the mechanical behavior is often correlated to limited stretch formability (Bohlen et al, 2018a). Forming limit curves revealed low formability in stretch forming conditions on the right side of the forming limit diagram but high formability on the left side, which in the context of this study compares to a strain path of the uni-axial tension test.…”

“…Conventional sheet rolling is carried out with high technical effort as the degrees of deformation per rolling pass need to remain low (Friedrich and Mordike, 2006). Processing of sheets via extrusion has also been described, which requires (and allows) a single high deformation processing step (Hsiang and Kuo, 2003;Bohlen et al, 2016Bohlen et al, , 2018aWang et al, 2016). This enables forming microstructures and textures that could not be produced by conventional production methods like casting or rolling (Gall et al, 2013).…”

“…Geometrically, an easier activation of basal slip during mechanical testing parallel to ED is then realized and an increase in the ductility of these materials enabled (Stanford and Barnett, 2008b;Zhou et al, 2013;Jiang et al, 2016). However, in the case of extrusion of flat profiles (without the rotational symmetry) also such alloys tend to form strong textures even if the alignment of basal planes may not preferentially be parallel to the sheet plane (Gall et al, 2013;Bohlen et al, 2018a). To give an example, extruded sheets from rare earth alloys ZE10 and ME21 in Bohlen et al (2016) show strong textures, while extruded round bar counterparts of the same or comparable alloys showed weak textures (Bohlen et al, 2010;Nascimento et al, 2010).…”

Modification of Microstructure and Texture in Highly Non-Flammable Mg-Al-Zn-Y-Ca Alloy Sheets by Controlled Thermomechanical Processes

“…In case of a weakened basal-type texture or non-basal texture components, it is expected that <a> dislocations with a relatively low CRSS contribute to accommodating the deformation along the ND. It was reported that texture weakening can be achieved by alloying Mg with yttrium (Y) and rare earth (RE) elements 2 of 9 such as cerium (Ce) or neodymium (Nd) [1][2][3][4][5]. Indeed, increased ductility, formability and strength have been observed in the sheet that has a weaker texture [6].…”