Effects of Casting Process on Structure and Mechanical Properties of Mg-12Zn-1Y Alloy
The icosahedral quasicrystal I-phase(Mg3Zn6Y)can be formed in the Mg-Zn-Y alloys with specific Zn and Y content,of which the microstructure in the conventional casting is usually coarse and difficult to exert performance advantages.The microstructure and mechanical properties of Mg-12Zn-1Y alloy prepared by gravity casting,squeeze casting and rheo-squeeze casting(RSC)were investiagted.The results reveal that in the gravity casting specimen,a large number of I-phase and Mg7Zn3 phase are gathered,while the squeeze casting process contributes to the morphol-ogy transformation of I-phase into fine lamellar,and the decrement of Mg7Zn3 phase.In the RSC process,with the increase of ultrasonic power applied during the stage of slurry-preparation,α-Mg grains are significantly refined and spheroidized,and the lamellar spacing of eutectic structure is obviously reduced.However,the concentration of eutectic structures appears when ultrasonic power continually is increased to 2 400 W.When the ultrasonic power is 1 600 W,the mechanical properties of the alloy are desirable,where the yield strength,tensile strength and elongation reach 185 MPa,276 MPa and 6.8%,which are 35.0%,24.9%and 142.9%higher than those of squeeze casting ones,respectively.
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