The Study On The Mg-Bi Alloy As Well It’s Microstructure And Properties Under Differently Prepared States

Heat-resistant magnesium alloys have a number of desirable features, including low density. High strength-to-weight ratio, good conductor of heat and good resistance to creep, and they are now increasingly used in industry and have great prospects in various fields. Mg-Bi alloy has a good thermal stability and creep property compared with Mg-RE alloy because of the Mg₃Bi₂’s melting point of 821℃. Mg-Bi alloy has the potential to develop a newly good heat-resistant magnesium consequently.In this paper Mg-Bi binary alloy is prepared by squeezing casting and extrusion deformation, the addition of Bi was 2wt.%, 4wt.%, 6wt.%, 8wt.%, 10wt.%, 12wt.%, 14wt.%, 16wt.% respectively. The microstructure and mechanical properties under as-cast / extruded and heat treatment conditions are investigated by optical microscopy（OM）, tension test at room temperature, X-ray diffraction（XRD）, scanning electron microscope （SEM ）and energy dispersive spectrometer （EDS）.Results show that the microstructure of Mg-Bi binary alloys is consisted ofα-Mg and Mg₃Bi₂ phase, the elongations of casting Mg-Bi alloy reduces and the ultimate tensile strength increase gradually with the increase of Bi content. When the content of Bi reaches up to 10wt.%, the ultimate tensile strength of alloy starts to reduce. After extrusion at 450℃for 3h with extrusion ratio of 12.76, the ultimate tensile strength and the elongations of Mg-Bi alloy increase gradually with the increase of Bi content. When the content of Bi is up to 12wt.%, it’s ultimate tensile strength is 219.68MPa and the elongation is 13.43%. The mechanical property of as-extruded Mg-Bi alloys stems from grain refinement and the phase strengthening of Mg₃Bi₂ phase. When the content of Bi is up to 12wt.%, the mechanical property of alloy starts to reduce due to the formation of a lot of coarse Mg₃Bi₂ phase.Mg-6Bi binary alloy preparing by squeezing casting is heat treated with the process of solution treatment temperature of 530℃and keeping time of 32h subsequently followed by the aging treatment of temperature 160℃and keeping warm 40h. The extruded Mg-6Bi alloy after 32h heat treatment under 530℃, the refined second phase Mg₃Bi₂ is well-distributed in the matrix, thus, the property is enhanced significantly.