Effects of scandium addition on microstructure and mechanical properties of ZK60 alloy

The effects of Sc addition on the microstructure and mechanical properties of the ZK60 wrought magnesium alloy were investigated by using optical microscope, scanning electron microscopy, X-ray diffraction and tensile testing. The experimental results show that a minor Sc addition to ZK60 alloy has an obvious effect on the refinement of the microstructure of the ZK60 alloy. During hot extrusion, incomplete dynamic recrystallization occurs in all the alloys, and the recrystallized grains become much finer with increasing Sc addition. The tensile strengths of ZK60 evidently increase with the addition of Sc, but the elongations decrease. The ZK60 alloy with 0.6% (mass fraction) Sc addition is found to have the tensile strength of about 350 MPa and the yield strength of about 280 MPa. After T6 heat treatment, the tensile strength of the alloy containing 0.6% Sc remains almost unchanged. However, the yield strength of the alloy increases up to 352 MPa, and the ratio of the tensile strength to the yield strength is close to 1.