Effects of segregation defects in the practical produced ZL205A castings on mechanical properties

fracture morphology

composition and molten temperature were analyzed by SEM（scanning electron microscope）

EDS（energy dispersive spectrometer） and DSC.It is found that segregation defects have the obvious effects on mechanical properties of the alloy castings.As the grades of segregation defects increase

the trend is decreased for the tensile strength which is more than 360 MPa

the yield strength which is all more than 280 MPa changes slightly

and the elongation is quickly decreased

which is almost lower than 4%

and all micro-hardness values are higher than 100.The fracture mechanism of the samples with defects free is characterized by ductile fracture while that of one with segregation is characterized by inter-crystalline brittle fracture.The substrate composition is mainly composed of α-Al solid solution with undissolved Al2Cu phase distributed along grain boundary.Melting temperature of eutectic phase Al2Cu reaches 544℃ and melting temperature of α-Al solid solution phase is in range of 625～640℃.The cards of segregation defect grades have been presented based on property testing results.