Effect of texture on the mechanical properties and formability of magnesium wrought materials

With the purpose of evaluating texture hardening in magnesium alloys, the c rystallographic texture and mechanical properties at room and elevated temp eratures of extruded bars and rolled sheets were studied. Cast ingots were used as the reference materials, since they exhibited nearly isotropic orie ntation distribution. Formability of AZ31 sheet was evaluated at room and e levated temperatures by the Erichsen test, conical cup test and forming lim it diagram. Strong texture is observed in magnesium wrought materials in wh ich the basal plane is oriented parallel to the extrusion or rolling direct ion. As a result, tensile strength of magnesium wrought materials increased by 15 to 20% due to texture hardening at room temperature. The AZ31 alloy sheet is highly anisotropic at room temperature with high r-value above 4, resulting that forming limits in biaxial tension are much lower than those in uniaxial tension. However, this anisotropy decreases with increasing for ming temperature and no texture hardening is found at 473 K. In this respec t, formability of magnesium alloys sheets in terms of Erichsen and conical cup values is remarkably poor at room temperature but appreciably improves with increasing temperature. Sheet forming of magnesium alloys is practical ly possible only at the high temperature range where plastic anisotropy dis appears.