An Unusual Texture Evolution in Extruded Mg–14Gd–Based Alloy during Annealing

Abstract

Texture evolution during annealing in various wrought Mg alloys is still controversial and texture control is an effective way of reducing mechanical anisotropy and improving secondary formability for Mg alloys. In this study, the electron backscattered diffraction (EBSD) method is used to monitor the texture evolution during the annealing process of a Mg-14Gd-2Ag-0.5Zr extruded bar. The novel phenomenon, that is, the texture evolution from <0001>?ED to <0001> ||ED, or rather, the increase fraction of grains with <0001> ||ED accompanied by the decrease fraction of grains with <0001>?ED, is found and discussed in the high-RE containing Mg alloy for the first time. The effect factors, stored energy in different textured grains and grain boundary misorientation, are mentioned to analyze the texture evolution.Texture control is an effective and important way of reducing mechanical anisortropy and improving the secondary formability for Mg alloys. On the one hand, the texture is related with the alloying elements. A strong basal texture with <0001>?ED (extrusion direction) would develop during extrusion of conventional Mg alloys such as AZ31 and AZ61. [1][2][3][4] While the rare earth (RE) containing Mg alloys exhibit weaker basal textures during extrusion compared with the RE-free alloys such as AZ31 and AZ61. [5][6][7][8][9][10] It has been reported that addition of little La or Gd element can produce a weak texture with <11-21>||ED orientation during lower extrusion temperature, [10] and the extruded rods with high content of Gd exhibit a weak texture with <0001>||ED orientation. [11][12][13] On the other hand, the process technologies and subsequent heat treating can affect the texture. The texture evolution of strong texture with <0001>?ED in conventional extruded Mg alloys during annealing has been widely reported. [1,4] For example, the main <10-10>||ED texture can evolve into <11-20>||ED one during annealing in extruded AZ31 alloy due to the preferential growth of grains having <11-20>||ED texture component by a high mobility of boundaries. [1] Some researchers also refer to the extrusion texture in RE-containing Mg alloys. [5][6][7][8][9][10][11][12][13][14][15][16][17][18] However, the texture evolution of Mg alloy with the high content of Gd during annealing has not been investigated in detail in previous literature. The extruded Mg-14Gd-2Ag-0.5Zr has exhibited a good combination of strength and ductility and has the great potential in engineering applications. [13] Therefore, in this work, we further studied the texture evolution of this extruded alloy during annealing, and this paper reports the novel phenomenon about the texture evolution, which contribute to the texture control of high-performance Mg-RE alloys. Experimental SectionThe Mg-14Gd-2Ag-0.5Zr (wt%) alloy investigated was prepared from purity Mg, Gd, Ag and Mg-33Zr (wt%) master alloy in a mild steel crucible under a protection of CO 2 and SF 6 atmosphere. The ingot was manufactured by direct-chill semicontinuous casting method. The as-cast bill...

Microstructure, Deformation, and Property of Wrought Magnesium Alloys

“…Additions of Zn or Ag [255][256][257][258] to Mg-RE alloys containing large amounts of RE elements lead to elimination of the RE-texture components that are commonly observed in dilute Mg-RE alloys. For a Mg 89 Y 7 Zn 4 (at.…”

“…Textures of the extruded and the annealed samples of Mg-14Gd-2Ag-0.5Zr (wt pct) alloy are shown in Figure 49(c). [258] The alloy was extruded at 450°C, a ram speed of 0.1 mm s À1 , and an extrusion ratio of 28:1. The as-extruded microstructure has a basal texture, with 10 10 // ED.…”

“…It was found that adding Nd and increasing the Nd content resulted in gradually weakened basal textures in which the predominant orientations changed with the extrusion condition. For the Mg-1Mn-0.5Nd alloy (MN10), its microstructure had a weaker basal texture than the Mg-1Mn alloy, with a dominant texture component of 10 Mg-15Gd-1Zn, [257] and (b) Mg-5.3Y-4.7Gd-1.6Ag-0.3Zr [258] (wt pct) alloys. (c) Inverse pole figures of the extruded and the annealed microstructures of Mg-14Gd-2Ag-0.5Zr (wt pct) alloy.…”

“…Adapted from Refs. [256][257][258]. the microstructure changed from A+B to A+B+C to A+C to A, with an increase in the extrusion temperature and speed.…”

Tailoring the Rolling Texture of AZ31 Mg Alloy with Calcium and Tin Addition

“…Magnesium (Mg) was regarded as one of the most promising candidates for such purpose as it is the lightest structural metal. Alloying is one of the effective ways to promote the mechanical properties of Mg . The alloy element of Mg alloys can be classified into two groups based on its solubility at elevated temperature.…”