Enhancement of Stretch Formability at Room Temperature by Addition of Ca in Mg-Zn Alloy

Abstract

The stretch formability of a rolled Mg-1.5Zn-0.1Ca alloy sheet was investigated at room temperature. The Mg alloy showed a large Erichsen value of 8.2. This is due to a reduction in intensity of basal plane texture and a spreading of the basal poles towards the transverse direction. It is suggested that solid solution of Ca atoms into Mg plays a critical role in the unique texture formation. Activation of non-basal slips by dilute Ca addition was hypothesized to be related to the unique texture formation. [doi:10.2320/matertrans.M2009385] (Received November 18, 2009; Accepted January 18, 2010; Published March 3, 2010) Keywords: magnesium alloys, rolling, texture, stretch formability Magnesium alloys are promising structural light materials because of their high specific strength, high specific stiffness and so on. The use of Mg alloys is expanding, particularly in automobile industry and consumer electronics industry. For their greater applicability, high formability Mg alloy sheets should be developed. However, (0002) basal planes are aligned parallel to the rolling direction (RD) and the intense basal plane texture is formed during rolling, results in poor formability at room temperature in rolled Mg alloy sheets.Recently, Mg alloy sheets showing high stretch formability at room temperature have been developed through two means. One is improved rolling technologies such as differential speed rolling, 1-3) cross rolling 4) and high temperature rolling. 2,3,5,6) The intensity of basal plane texture is reduced by the improved rolling methods, and therefore, the stretch formability of the rolled Mg sheets is enhanced. Huang et al. 2) showed that a large Erichsen value of 9.5 is obtained in AZ31 Mg alloy produced by differential speed rolling at high temperature of 823 K. Addition of special elements such as Ce, Y, Gd and La is another route for enhancement of stretch formability at room temperature in Mg alloys. 7-9) For example, it has been reported that a rolled Mg-1.5 mass%Zn-0.2 mass%Ce alloy sheet shows a large Erichsen value of 9.0 at room temperature. 7) Addition of the special elements gives rise not only to a reduction in intensity of basal plane texture, but also to a spreading of the basal poles towards the RD or the transverse direction (TD). [8][9][10][11][12][13][14] Such unique texture by the addition of special elements is obtained during extruding as well. [15][16][17][18] However, these additional elements are rare and high cost materials. This is a big problem for commercial applications.The present paper describes enhancement of stretch formability at room temperature by very low Ca addition of 0.066 mass% to Mg-1.52 mass%Zn alloy. The rolled Mg-ZnCa alloy exhibited a large Erichsen value of 8.2 at room temperature, while a rolled Mg-Zn alloy showed a low Erichsen value of 3.4 at room temperature. This finding of the enhanced stretch formability by the Ca addition is very interesting in terms of both commercial and scientific aspects.An extruded Mg-1.52 mass%Zn-0.066 mass%Ca alloy (Mg-1.5Z...

Effects of Ca on Tensile Properties and Stretch Formability at Room Temperature in Mg-Zn and Mg-Al Alloys

“…However, it has been recently reported that addition of specific elements such as Ce, Y and Ca give rise to a significant enhancement in stretch formability at room temperature in Mg alloys. [1][2][3][4][5][6][7][8][9][10] For example, Mg-1.5 mass%Zn-0.1 mass%Ca alloy exhibited a large Erichsen value of 8.2 at room temperature. 5) This value is comparable with the stretch formability of commercial wrought aluminum alloys.…”

“…[1][2][3][4][5][6][7][8][9][10] For example, Mg-1.5 mass%Zn-0.1 mass%Ca alloy exhibited a large Erichsen value of 8.2 at room temperature. 5) This value is comparable with the stretch formability of commercial wrought aluminum alloys. 11) In general, because the critical resolved shear stresses for nonbasal slips are much larger than that for the basal slip 12,13) and the non-basal slips hardly occurs at room temperature in Mg based materials, they exhibit poor plastic formability at room temperature.…”

Enhancement of Room Temperature Stretch Formability of Mg–1.5 mass%Mn Alloy by Texture Control

“…11) In addition, new alloy design technologies for the improvement of roomtemperature formability have also been developed, in which special elements such as rare-earth metals and calcium, are added in minute quantities to the MgZn alloys. 12,13) It is well known that compared to various other metals, pure Mg has high damping properties. However, damping properties of Mg alloys such as MgAlZn are not as high as that of pure Mg, because dislocation damping, which is the main damping mechanisms of Mg, is associated with a significant decrease in damping properties with increase in solute concentrations.…”

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

“…[4][5][6][7][8][9][10][11] For example, in the case of rolled Mg-Zn alloys, it was reported that a rolled Mg-1.5 mass%Zn-0.2 mass%Ce alloy sheet showed excellent sheet formability corresponding to the 5000 series Al alloys. 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).…”

“…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.…”