Rare Earth Elements Of Dy, Y And Deformation Process On The Microstructure And Mechanical Properties Of Zk60 Magnesium Alloy,

By using of mechanical property testing machine, optic microscopy(OM), scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD), the ZK60 magnesium alloy were investigated for microstructure and mechanical properties through alloying , hot extruding , hot rolling and annealing experiment results are obtained as follows:1. It can be observably refined of both the as-cast and the as-extruded microstructues by added 1wt.% Dy or 1wt.%Y in the ZK60 alloy. The effect of Y addition on grain refinement is better than that of Dy addition while the effect is the best for the co-addition of Dy and Y. Owing to the co-addition of Dy and Y ,the grain size of as-cast ZK60 alloy can be reduced from 105μm to 35μm and as-extruded ZK60 alloy can be reduced from 20μm to 4μm. The tensile strength of the alloy with the addition of Y decreased while increased in the alloys with the single addition of Dy. Compound add two RE elements made the tensile strength, yeile strength and elongation of alloy increases to 210.2MPa,115.6MPa and 8.6%, which increase 5.3%,17.1%,177.4% compared ZK60 alloy without RE element .The variation of the mechanical property of the alloys with the addition of Dy and Y could be ascribed to the interchange of site of the atoms in the quasi- crystalline lattice and the propotion of the second phases that formed in the alloys.2. Because of the textures softening and second phase dispersive distribution ,The elongation of the extrude-rolling sheet reaching to 16.7%, which increases 74% compared normal rolling sheet; subgrain strengthening of normal rolling is stronger then grain refine of the extrude-rolling which lead to the mechanical properties of the normal rolling sheets have been increased in various degrees. Theσ_b andσ_0.2 of the normal rolling sheet was above 316.56 MPa and 133.56 MPa while only 307.10 MPaå'Œ124.12 MPa of the extruded-rolling sheet. 3. Extruded-longitudinal rolling was benefit to reduce the strength anisotropy of ZK60 wrought magnesium alloy sheet, while extruded-transverse rolling was benefit to reduce the elongation anisotropy of ZK60 wrought magnesium alloy sheet. The best improvement of anisotropy was achieved at 300℃for 1 hour and air-cooled.