The effects of different contents of scandium on the microstructure and mechani-cal properties of Al-7Mg alloy sheets were studied by means of metallographic microscope(OM),scanning electron microscope(SEM),differential scanning calorimetry(DSC)and tensile test.The experimental results show that scandium plays a significant role in reducing the central segregation zone caused by rapid solidification and high magnesium content in twin-roll casting.After increasing the content of scandium,the grain size of twin-roll casted sheet decreases gradually,and the secondary dendrite arm spacing can be reduced to 9.92 μm minimum.The segregation degree of each element decreases and the segregation is basically eliminated,and the number of non-equilibrium eutectic phases in the alloy also shows an obvious downward trend.At the same time,with the scandium content increasing from 0.1wt.％to 0.2wt.％,the yield strength,tensile strength and elongation of Al-7Mg alloy increase by 57 MPa,35 MPa and 4.3％,respectively.The addition of scandium ele-ment increases the nucleation rate during solidification and restrains the growth of dendrites.At the same time,scandium element improves grain refinement,reduces segregation,and obviously improves the mechanical properties of the alloy.
关键词
双辊铸轧/高镁铝合金/偏析缺陷/组织与性能
Key words
twin-roll casting/high-magnesium aluminum alloy/segregation defect/mi-crostructure and properties
维普
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