Element segregation behavior of aluminum-copper alloy ZL205A

In aluminum-copper alloy, the segregation has a severe bad effect on the alloying degree, strength and corrosion resistance. A deeper understanding of element segregation behavior will have a great signif icance on the prevention of segregation. In the study, the element segregation behavior of ZL205 A aluminum-copper alloy was investigated by examining isothermally solidifi ed samples using scanning electron microscopy and energy dispersive spectroscopy. The calculated results of segregation coeffi cients show that Cu and Mn are negative segregation elements; while Ti, V and Zr are positive segregation elements. The sequence of element segregation degree from the greatest to the least in ZL205 A alloy is Cu, Mn, V, Ti, Zr and Al. The density of residual liquid is expected to increase with a decrease in the quenching temperature ranging from 630 ℃ to 550 ℃. The calculated results conf irm that the quenching temperature has an insignif icant effect on the liquid density; and the variation of density is mainly due to element segregation. Consequently, segregations of Al, Cu and Mn lead to an increase in density, but Ti, V and Zr present the opposite effect. The contribution of each element to the variation of the liquid density was analyzed. The sequence of contributions of alloying elements to the variation of total liquid density is Cu>Al>Mn>V>Ti>Zr.

ZL205A合金块状偏析相缺陷的研究

以ZL205A合金铸件块状偏析缺陷为研究对象,研究了超声熔体处理、时效处理对块状偏析、显微组织及显微硬度的影响。结果表明,超声处理熔体并不能消除ZL205A合金中的块状偏析,对其尺寸和分布无影响,但对合金组织有一定的细化作用;时效时间对块状偏析相尺寸无影响,但对块状偏析相的显微硬度有影响,其显微硬度随时效时间的增加呈现先提高后减小的趋势,时效4 h时达到峰值硬度165.1 HV;均匀化热处理不能减轻或消除块状偏析。