Enhancing tensile strength of Mg-Al-Ca wrought alloys by increasing Ca concentration

The tensile strengths of the as-extruded Mg-Al-Ca ternary alloys at both ambient and elevated temperatures are enhanced via adding a high content of Ca element up to 6 wt%. High-temperature strength of the present rare-earth-free Mg alloys can be even compared with those of the reported Mg-RE alloys. The as-extruded Mg-6Al-6Ca (wt. %, AX66) alloy exhibits a tensile yield strength (YS) of similar to 404 MPa and an ultimate tensile strength (UTS) of similar to 415 MPa at room temperature, and YS of similar to 225 MPa and UTS of similar to 265 MPa at 200 degrees C, respectively. For the AX66 alloy, the nucleation rates of dynamic recrystallized (DRXed) grains are larger than those of the AX62 and AX64 alloys due to the typical particle stimulated nucleation effect. A number of long-rod Al2Ca phase is dispersed at the grain boundaries of AX66 alloy, and a restricted degree of DRX is induced. Consequently, the majority of alpha-Mg matrix exists in the as-deformed state involving a high density of subgrains. The combined effects of grain refinement hardening, texture hardening and precipitation hardening guarantee the high strength. Specially, numerous micron-scale bulk (Mg, Al)(2)Ca phases are found to distribute among matrix, which play a critical role in maintaining the high thermal-resistance.