Effects of aging time on microstructures and mechanical properties of thixoforged AZ63 magnesium alloy were invstiagted.The results indicate that aging time affects the precipitation sites

volume fraction and shape of aging precipitation

and finally affects the mechanical properties and fracture behavior.The improvement of mechanical properties is attributed to the dispersion strengthen of continuous precipitation

and the decrease of mechanical properties is resulted from the harmful discontinuous lamellar precipitation.With the aging time increase

the fracture mode is transformed from intergranular into transgranular fracture.With aging at 215 ℃ for 2h

the tensile strength reaches 348 MPa

and hardness reaches 69（HV）with aged for 8h.Comparing with thixoforged AZ63 alloy

the tensile strength and hardness of the aged alloy are increases by 53% and by 26%

respectively.The fracture morphology is characterized by quasi-cleavage fracture.