Calcium and zirconium as texture modifiers during rolling and annealing of magnesium–zinc alloys

Abstract

Rolling experiments were carried out on a ternary Mg-Zn-Ca alloy and its modification with zirconium. Short time annealing of as-rolled sheets is used to reveal the microstructure and texture development. The texture of the as-rolled sheets can be characterised by basal pole figures with split peak towards the rolling direction (RD) and a broad transverse angular spread of basal planes towards the transverse direction (TD). During annealing the RD split peaks as well as orientations in the sheet plane vanish whereas the distribution of orientations tilted towards the TD remains. It is shown in EBSD measurements that during rolling bands of twin containing structures form. During subsequent annealing basal orientations close to the sheet plane vanish based on a grain nucleation and growth mechanism of recrystallisation. Orientations with tilt towards the TD remain in grains that do not undergo such a mechanism. The addition of Zr delays texture weakening.

The Influence of Strain Path on Rare Earth Recrystallization Textures in a Magnesium-Zinc-Rare Earth Alloy

“…This unique TD spread texture has been observed in a variety of magnesium-Zn-RE alloys including those containing Ce, Gd, and Nd. [4,[10][11][12][13] Similar textures have been observed in alloys which contain Ca rather than RE. [10] In the as-rolled condition (hot rolling) such materials often show a spread in basal poles toward the TD, even if a split toward the RD is retained.…”

“…[4,[10][11][12][13] Similar textures have been observed in alloys which contain Ca rather than RE. [10] In the as-rolled condition (hot rolling) such materials often show a spread in basal poles toward the TD, even if a split toward the RD is retained. [4,12,13] The pronounced spread and split toward the TD emerges during recrystallization.…”

“…It is argued that Ca behaves similarly since it shares these attributes. [10] A small number of studies have attempted to understand the development of texture in Mg-Zn-(RE,Ca) alloys during deformation [4,10,15] and annealing. [4,10] During cold deformation, it has been argued [15] that twinning dominates texture evolution, and the main effect of combined additions (of Ca and Zn) is to suppress twin growth, leading to a lower twin fraction (for a given applied strain) and nucleation of more twin variants within a grain.…”

“…[15] The importance of recrystallization (after warm rolling) in producing the characteristic TD spread in Mg-Zn-(Ca,RE) rolled sheet has been noted in several studies. [4,10,12,13] It has been observed that during recovery and recrystallization, TD-oriented grains appear more resistant to recrystallization, whereas those with basal poles spread (or split) toward the rolling direction (RD) are consumed, leading to dominance of the TD spread grains. The TD spread grains are seen to emerge from shear bands in the material.…”

Microstructural changes in an extruded Mg Zn Y alloy reinforced by quasicrystalline I-phase by small additions of calcium, manganese and cerium-rich mischmetal

“…Calcium and RE additions refine the microstructure of magnesium alloys and improve the strength at room and high temperatures through the formation of hard intermetallic phases [2,[15][16][17][18][19][20][21]. Moreover, both elements contribute to randomize the basal texture [22]. The complete insolubility of manganese produces a fine dispersion of manganese particles in the magnesium matrix which strengthens the alloy through the refining of the grain size in magnesium alloys [23,24].…”