一种亚共析铀铌合金的凝固特点及显微偏析研究

分析了一种亚共析U-Nb合金的凝固过程,获得了该合金的固相线、液相线温度和固-液两相区的残余液相体积。发现凝固末期残余液体不能形成液体网,凝固枝晶很快互相连接,形成一些较大的孤立的液体池。凝固末期这种不能补缩的液体池易形成严重的疏松,理论初步计算合金的显微疏松量约为1.6%。发现合金中铌是严重的负偏析合金元素,凝固中期和凝固末期偏析系数k仅为0.16和0.11,极易在枝晶干偏聚造成枝晶偏析。

Solidification Characteristics and Micro-Segregation of Sub-Eutectiod U-Nb alloy

The solidus, liquidus and volume of residual liquid were achieved by study the solidification behavior of a sub-eutectiod U-Nb alloy. It is found under metallographic observation that their microstructure reveals as the dentritic crystal connected each other and residual liquid separated by solid phase during terminal solidification. Thus, serious micro-porosity form easily in oisolated residual liquid area for the filling channels plugging and residual liquid unable to fill the pore, and the amount of porosity in casting is about 1.6% derived from theoretical calculation. The chemical analysis results showed that segregation coefficients of niobium at intermediate and terminal solidifaction are 0.16 and 0.11 respectively, which indicated that Nb is a strong negative segregation element and it severely cluster in the dendritic area.