论文部分内容阅读
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)_7C_3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~(-0.234)V_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)C_0G)/(D⊿T) R~(0.335)
During the directional solidification, the primary carbide (Fe, Cr) _7C_3 precipitates in a hexagonal rod shape with hypereutectic Fe-3.12% C-35.9% Cr and Fe-2.80% C-33.1% Cr alloy. As the solidification rate (R) increases, the primary crystal spacing (λ) becomes smaller and obeys the following formula: λ = BR -0.234 Meanwhile, the average primary crystallite diameter (d) and the volume fraction ) Is also decreased with the increase of solidification rate, the following relationship: ■ = AR ~ (-0.234) V_f = CR ~ (-0.394) In this experiment, the high carbon content, primary crystal ■, λ, V_f , Have increased. The initial growth rate of primary carbides is: R_r = A (?) 2 (?) G /? TR ~ (0.569) When the solidification rate decreases or the carbon content decreases, the primary carbide will change from a solid hexagonal bar Into a hollow hexagonal stick. In this paper, the degree of undercooling of the primary crystal is deduced and the following formula is obtained: Δ θ = (ABm (K-1) C_0G) / (D⊿T) R ~ (0.335)