High cycle fatigue improvement by heat-treatment for semi-continuous casting Mg96.34Gd2.5Zn1Zr0.16 alloy

High cycle fatigue behavior of casting Mg96.34Gd2.5Zn1Zr0.16 alloy was investigated for its improvement by heat-treatment. After solution treatment (T4, 10 h@773 K) or solution treatment plus artificial aging (T6, 10 h@773 K+128 h@473 K), fatigue strength of this alloy was found to be enhanced. The T6-treated alloy achieved the highest fatigue strength, 130 MPa, being 25 MPa and 18 MPa greater than those of the as-cast and T4-treated alloy, respectively. The average fatigue life of the heat-treated alloys is longer than that of the as-cast alloy a given stress amplitude. For the distribution of fatigue life, a fatigue life gap spanned from 105 to 107 can be observed in the as-cast and T4-treated alloy. Such a gap is absent after the alloy received artificial aging. The mechanism for the high cycle fatigue behavior of the casting alloy after heat-treatment was also discussed.