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The tensile tests and the Erichsen tests at room temperature have been performed on seven kinds of Mg alloys: Mg-1.5Zn, Mg-1.5Zn-0.1Ca, Mg-3Zn, Mg-3Zn-0.1Ca, Mg-3Al, Mg-3Al-0.1Ca and Mg-1Al-1Zn-0.1Ca-0.5Mn alloys. In the Mg-Zn alloys, the 0.2% proof stress at 90, which was the angle between the tensile direction and the RD, was decreased by addition of Ca, while the 0.2% proof stress at 0 was increased by addition of Ca. Also, an increase in elongation to failure by addition of Ca at 90 was larger than that at 0 . However, such variations in tensile properties by addition of Ca were not found in the Mg-Al alloy. The stretch formability for the Mg-Zn alloys was significantly enhanced by addition of Ca, while the stretch formability of the Mg-Al alloy was not enhanced by addition of Ca. These results by the mechanical testing are ascribed to the variations in basal texture by addition of Ca.

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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...

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