Preparation of Mg-TM-Y (TM=Transition Metal) Alloys with Long Period Stacking Ordered Phase and their Superior Mechanical Properties

Abstract

Mg-Ni-Y alloy with composition ratio of 1 : 2 (Ni : Y) consisted of Mg, and 18R-type long period stacking ordered (LPSO) phases, whereas composition ratio of 1 : 1 (Ni : Y) consisted of Mg,14H-type LPSO and Mg2Ni phases, respectively. After hot-rolling at 693K, strong basal texture parallel to the plane sheet was formed in the LPSO, and Mg phases. Tensile test was performed along rolling direction (R.D) from room temperature (R.T) to 573K. The Mg98Ni1Y1, Mg96Ni2Y2, Mg94Ni3Y3, Mg97Ni1Y2 and Mg94Ni2Y4 rolled sheets exhibited 0.2% proof stress (σ0.2) of 232MPa, 255MPa, 358MPa, 337MPa and 393MPa, and elongation (δ) of 6%, 5%, 7%, 15% and 7% at R.T, respectively. The σ0.2 of the Mg-Ni-Y rolled sheet tend to increase with increasing of area fraction of the LPSO phase. After annealing at 773K for 0.6ks, the δ of Mg-Ni-Y rolled sheet tend to increase, while the σ0.2 decreased due to randomization of the Mg phase by re-crystallization. The Mg-Ni-Y rolled sheets exhibited high σ0.2 above 200MPa at 473K. Additionally, it was noted that σ0.2 of the Mg94Ni2Y4 rolled sheet exhibited 329MPa at 473K and 211MPa at 573K. Thus, the LPSO phase have high thermal stability and is attribute to strengthening of the Mg-Ni-Y alloy sheet at high temperature.