Study On Microstructures And Properties Of Mg-Al-Sn-Y Alloys

In recent years, with the increasing demand for lightweight construction and energy-saving emission, development of magnesium alloys is more and more important.The rare earth element Y and the element Mn were added into Mg-Al-Sn alloy in this paper, and the eight different compositions experiment alloys were prepared in an induction furnace under Ar atmosphere. The microstructure, mechanical properties and corrosion properties of experiment alloys were investigated by X-ray fluorescence spectrometry(XRF), X-ray diffractometer(XRD), optical microscopy(OM), scanning electron microscopy(SEM) equipped with an INCA Energy dispersive X-ray spectrometer(EDS), tensile tester, electrochemical corrosion workstations, stretching and hydrogen evolution experiments,making clear the effect of Y and Mn on microstructure, mechanical properties and corrosion properties of experiment alloys.The microstructure, mechanical properties and corrosion properties of Mg-4Al-2Sn-xY(x=0, 0.5, 1.0, 1.5 wt.%) alloy were investigated. The as-cast Mg-4Al-2Sn alloy is dendritic morphology, it consists of α-Mg、Mg17Al12 and Mg2 Sn phase. When element Y was added into alloys, the as-cast alloys dendrite refining and generate a new bulk phase Al2 Y phase. With the Y contnet increasing, the amount of Al2 Y phase gradually increasing, the size of Al2 Y phase gradully increasing and grew up together, while the amount of Mg17Al12 phase decreasing and distributed continuous become dispersed along the grain boundaries. Mechanical properties of cast alloys decresse with addtion of Y content increases. After homogenization the alloy by hot extrusion, alloy grain refinement, there is some dynamic recrystallization region, and a small amount of fine Mg2 Sn phase precipitates along the grain boundary, the mechanical properties of the alloy with Y added a certain degree of improvement. Adding element Y can weaken the Mg-4Al-2Sn alloy tension and compression asymmetry, when the content of Y is 1.0 and 1.5(wt.%), CYS / TYS value of alloys 0.93 and 1.06. Y may be added to improve the corrosion resistance of the alloy after the corrosion resistance of Y with increasing content of the alloy increased in the first increase, extruded Mg-4Al-2Sn-0.5Y alloy corrosion resistant was best.The microstructure and mechanical properties of Mg-4Al-2Sn-xY-0.4Mn alloy were investigated. The as-cast Mg-4Al-2Sn alloy is dendritic morphology, it consists of α-Mg, Mg2 Sn, Mn and Al8Mn5 phase. When element Y was added into alloys, the as-cast alloys dendrite morphology changed and generate a new bulk phase second phase. With the Y contnet increasing, the amount of Al2 Y phase gradually increasing, the size of Al2 Y phase gradully increasing and grew up together, while the amount of Mg17Al12 phase decreasing and distributed continuous become dispersed along the grain boundaries. After hot extrusion of homogenized alloys, the grains become small and existed some dynamic recrystallization regions. Compared with the Mg-4Al-2Sn-xY alloys, dynamic recrystallization regions increased. However, the mechanical properties of homogenize-extruded Mg-4Al-2Sn-xY-0.4Mn alloys have little change with Y increased. After adding Mn, element Y effect on mechanical properties of the alloy weakened. Compared with the mechanical properties of Mg-4Al-2Sn-xY alloy, trace Mn can improve strength of the alloy.The microstructure, mechanical properties and corrosion properties of cast–extruded Mg-4Al-2Sn-xY-0.4Mn alloy were investigated. The Cast-extruded Mg-4Al-2Sn-xY-0.4Mn alloy exhibited fine equiaxal grain structure, you can see some dispersion nanoparticles Mg2 Sn phase precipitated along the grain boundary, and the alloy occured fully dynamic crystallization. The tensile mechanical properties at room temperature had a certain improvement with addtion of Y increases. However, compared with homogenized-extruded alloys,the tensile mechanical properties at room temperature had increased. The mechanical properties at 200 oC temperature had little change with the addition of Y increases, but the elongation at 200 oC temperatures reached more than 70%. The corrosion resistance of alloy first increased and then decreased again increased with the addition of Y increases. The corrosion resistance of Mg-4Al-2Sn-0.5Y alloy is best.Therefore, Mg-4Al-2Sn alloy was optimized by adding elements Y, Mn and heat treatment. According to the mechanical properties, corrosion resistance, and economic considerations, cast-extruded Mg-4Al-2Sn-0.5Y-0.4Mn alloy performance was best. The yield strength, tensile strength and elongation of room temperature were 216 MPa, 303 MPa and 12.3%, respectively. The yield strength, tensile strength and elongation of 200 oC high temperature were 140 MPa, 170 MPa and 74.6%, respectively. And the density of self-corrosion current was 2.0511E-6 A/cm2.