Study On Microstructures And Properties Of Mg-Mn-Zn-Cu-xY-Ca Alloys

Magnesium and magnesium alloys are used in aviation, aerospace, automotive,electronics and other fields due to their high strength, easy recycling, low density, andexcellent damping capacity, electromagnetic shielding and thermal conductivity.Magnesium and magnesium alloys are one of ideal metals exhibited simultaneouslywith structure and function, however，pure magnesium has low strength， tensilestrength is100MPa, elastic modulus is45GPa which limit the further application ofmagnesium and magnesium alloys. So the high-strength magnesium alloy is a hotresearch topic this year.Different amounts xY(x=0,1,2,3,4) was been added on the basic ofMg-Mn-Zn-Cu-Ca elements to achieve alloysin this paper. The elementsMg-Mn-Zn-Cu-and0.6%Zr were added to pure magnesium in this paper. The effect tofY contents on the microstructure of Mg-Mn-Zn-Cu-xY-Ca was been were studied byoptical microscopic, scanning electron microscopic equipped with energy dispersivespectroscopy, X-ray diffraction. micro-hardness and tensile testers were used to studythe effect of Y contents on the properties of Mg-Mn-Zn-Cu-xY-Ca.The results show that the adjunction of element Y can refine dendrite of cast alloys.The microstructure of cast alloys consist of coarse dendrite of α-Mg, compoundprecipitation along the precipitation and a small amount of crystalline precipitatecompounds. The microstructure show reticular and dendritic distribution. With theincreasing of Y content, second phase is gradually increasing.The clear eutecticgenerated as the addition of Y element. With the increasing of Y content, hardness of thealloys increases. Compared with cast alloys, second phase of alloys obviously decreaseafter solution treatment. However, the solution treatment was not completely, a part ofsecond phase still exist on the matrix after solution treatment.The cast alloys were extruded at350℃after solution treatment. Dynamicrecrystallization occurs during the extrusion process, the grain size of the alloys isobviously reduced. The second phase which is not completely dissolved on the matrixafter solution treatment was crushed during extrusion process. The crushed secondphase was distributed along along the extrusion direction, and the distribution of thesecond phase show flow line. Hardness of extruded alloys was significantly higher thanthe hardness of cast alloys. Due to the occurrence of recrystallization in alloys, the fine and equiaxed grain generated, and the distribution of the second phase in the alloysimpeded motion of dislocation, thus made the strength of alloys increase. Afterextrusion, properties of the4#alloy is preferably, the tensile strength is315MPa,theyield strength is308MPa. Different heat treatment processes were adopted to improvethe properties of the alloys. Study showed that properties of the alloys is after36h agingtreatment at180℃. After the aging treatment, the properties of the4#alloy ispreferably, the tensile strength is325MPa, the yield strength is312MPa. Compared withextruded alloys, properties of the alloys improved after aging treatment. The tensilestrength of0#alloy improved19MPa,3#improved8MPa4#improved10MPa. Theyield strength of0#alloy improved10MPa，3#improved20MPa4#improved4MPa...