Abstract:Effects of microstructure, phase composition, composition of scandium in AZ91 alloy on alloy’s mechanical and corrosion properties were investigated. The results show that grain size of Mg-Gd alloy drops with increase of gadolinium content, and crystal morphology transforms from dendrite to isometric crystal with gadolinium content of about 1%~3%. Correspondingly, grain size rises with increase of gadolinium content and crystal defects increases with gadolinium content of 3% above. Dendrite crystal is observed again when gadolinium content is up to 5%. The optimum mechanical properties at room temperature and 200 ℃ are improved to 261.6 MPa and 148.7 MPa respectively when gadolinium content is increased to 3%. Corrosion current density drops markedly opon adding gadolinium, while sel-corrosion potential rises slightly.