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

Abstract

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.

Effects of group II elements on the cold stretch formability of Mg–Zn alloys

“…The addition of Ca promoted grain refinement [32,33]. This may be because of the restriction of grain growth by the addition of Ca [17]. Precipitates were found in the Mg-Zn-X alloys from EPMA (results by EPMA are not shown in the present paper).…”

“…Sandlö bes et al [38] investigated the dislocation motion in the Mg-3 mass% Y alloy deformed at room temperature and they found that the hc + ai slip is significantly enhanced by the Y addition. Our observation [17] revealed that prismatic hai and hci slips occur in the Mg-Zn-Ca alloy tensile-deformed to 1% [17]. Therefore, it is suggested that non-basal slips are enhanced by the addition of Ca, resulting in the tilting of basal texture in Mg-Zn-Ca alloys.…”

“…Thus, a large directional dependence of the flow stress was found in the Mg-Zn-X alloys. The directional dependence of flow stress is likely to be primarily related to the texture [16,17]. The flow stresses of the Mg-Zn-X alloys tended to be lower than that of the Mg-Zn alloy, independent of the tensile direction.…”

“…Not only the basal hai slip, but also the prismatic hai slip was active in the Mg-Zn-Ca alloy [17]. Therefore, calculations in the present work were performed assuming that both the basal hai slip and the prismatic hai slip are active in Mg-Zn-X alloys.…”

“…It was recently reported that the addition of a small amount of 0.07 mass% Ca significantly enhances the cold stretch formability of Mg-Zn alloys [16,17]. This finding is very attractive for commercial applications because Ca is not a rare metal.…”