Characterization of Mushy Zone of ZWx2 (x=2, 4, 6) Magnesium Alloys

摘要

The potentials of Mg-Al system alloys for semi-solid forming have been extensively evaluated these years. In the present studies, mushy zone properties of the Mg-Zn system alloys, i.e. ZWx2 (x=2,4, 6), are characterized and analyzed by using cooling curve thermal analysis method and continuous torque measurement technique. The results show that T_(n1) (first characteristic temperature of primary crystal nucleation), T_(n2)(second characteristic temperature of primary crystal nucleation) and T_(ch) (temperature of dendritic coherency) decrease with the increasing of zinc content, and the temperature difference of (T_(n1)-T_(n2)) almost remains constant, while the temperature difference of (T_(n2)-T_(ch)) changes dramatically when Zn content increases to 6wt.%; The results also show that the f_(s-cc) (solid fraction of dendritic coherency) of ZWx2 alloys ranges from 0.4 to 0.51 while ZW22 and ZW62 alloys having higher f_(s-ch) and ZW42 alloy having the lowest f_(s-ch); also, strength of alloys in mushy zone does not develop until a certain fraction solid( corresponding to the dendrite coherency point) is reached. The results obtained by cooling curve thermal analysis method and continuous torque measurement techniques are comparable to each other.