【摘要】 过共晶Fe-3.12%C-35.9%Cr及Fe-2.80%C-33.1%Cr合金在定向凝固时,初晶碳化物（Fe、Cr）₇C₃以六角形棒状析出。随着凝固速度（R）的增加,初晶的间距（λ）变小,并服从下式:λ=BR^-0.234同时,初晶碳化物的平均直径（d）及体积分数（V_f）也是随凝固速度的增加而减少,有如下的关系:■=AR^-0.234V_f=CR^-0.394在本实验中,含碳量高者,初晶的■、λ、V_f,均增大。初晶碳化物的侧向生长速度为:R_r=A（?）2（?）G/△T R^0.569当凝固速度降低或含碳量减少,初晶碳化物将从实心六角形棒变成中空的六角形棒。本文并对初晶生长的过冷度作了推导,得出了下面的公式:△θ=（ABm（K-1）C₀G）/（D⊿T） R^0.335更多还原

【Abstract】 In the process of directional solidification,hypereutectic cast iron（Fe-3.12% C-35.9%Cr andFe-2.8% C-33.1%Cr）precipitates primary carbide（Fe.Cr）₇C₃ in theshape of hexagonal rod.With the increase of the solidification rate,the lamellarspacing of primary λ decreases and conforms to the following formula:λ=BR^-0.234Similarly,with the increase of the solidification rate,the average diameter a andthe volume fraction V_f of the primary carbide also decrease.The following formulasshow the relation of them:（?）=AR^-0.431V_f=CR^-0.394with the increase of the carbon content,（?）,λ and V_f of the primary increase.Theflank growth rate of primary carbide Rr conforms to the following formula:R_r=（AG/2⊿T）R^0.5（?）When the solidification rate and carbon content decrease,the hexagonal rod of theprimary carbide changes from a solid one to a hollow one.The analysis of theundercooling on the interface of the primary carbide resulted in the followingformula.:⊿θ=（（AB_m（K-1）C₀G）/D⊿T） R^0.335更多还原