Development of Heat-Treatable High-Strength Mg-Zn-Ca-Zr Sheet Alloy with Excellent Room Temperature Formability

Lightweight magnesium (Mg) alloys have attracted considerable attention for potential applications in the automotive industries. However, the low strength or poor formability at room temperature (RT) hinders the wider applications of wrought Mg alloy sheets. The newly developed a heat-treatable magnesium sheet alloy, Mg-0.6Zn-0.3Ca-0.1Zr (at. %), shows a large Index Erichsen value of 8.0 mm at RT in a solution treated condition. The excellent RT formability can be ascribed to a weak basal texture. Subsequent artificial aging at 170 degrees C for 4 h (T6) increases the 0.2% proof strength from 165 to 213 MPa. This improvement in strength by the T6 treatment is associated with a dense distribution of Guinier-Preston zones lying on the basal planes of the Mg matrix. Our finding overcomes the trade-off relationship of the room temperature formability and proof strength in Mg alloy sheets and this can be used as "bake hardenable" magnesium sheet alloy with excellent RT formability.