铈对Fe-4%Si合金凝固特征温度的影响及机制

Effect and Mechanism of Cerium on Solidification-Characteristics Temperatures of Fe-4%Si Alloy

针对不加Ce和添加Ce的Fe-4%Si合金,采用NETZSCH STA 449C型综合热分析仪测定其示差扫描量热(DSC)曲线,探讨添加Ce对Fe-4%Si合金近平衡凝固过程中特征温度的影响。利用液态金属冷却(LMC)定向凝固技术,对添加Ce的Fe-4%Si合金试样通过定向凝固实验保留固-液界面。采用岛津EPMA-1720H电子探针(EPMA),对添加Ce的Fe-4%Si合金定向凝固样品,进行长时间点定量分析,探索Ce在固-液界面处的富集。结果表明,添加Ce使Fe-4%Si合金近平衡凝固过程中液相线温度和固相线温度都有降低的趋势、结晶温度区间有增大的趋势。EPMA长时间点定量分析,证实了凝固过程中Ce能够以原子或夹杂物形式在固-液界面前沿的液相富集。界面处Ce的富集,可能阻碍凝固生长过程中原子的供应,进而影响Fe-4%Si合金的近平衡凝固特征温度及结晶温度区间。

The differential scanning calorimetric(DSC)curves of Fe-4%Si alloys with and without Ce addition were measured using a NETZSCH STA 449C integrated thermal analyzer,and the effect of Ce on the near-equi⁃librium solidification-characteristics temperatures of Fe-4%Si alloy was investigated.The liquid metal cooling(LMC)directional solidification technology was applied to freeze the distinct solid-liquid interface from high temperature to room temperature for further characterization.The aggregation of Ce in the liquid at the front of the solid-liquid interface of the Fe-4%Si alloy with Ce addition was determined using longstanding point quantita⁃tive analysis in a Shimadzu EPMA-1720H electron probe microanalysis(EPMA).The results showed that addi⁃tion of Ce resulted in reductions of the liquidus temperature and the solidus temperature and an increase of the solidification temperature range during the near-equilibrium solidification of Fe-4%Si alloy.The longstanding point quantitative analysis of Ce in the directional solidification sample using EPMA verified the enrichment of Ce in the liquid at the front of the solid-liquid interface of the Fe-4%Si alloy in the form of atoms or/and Ce-in⁃clusions.The enrichment of Ce in the solid-liquid interface can hinder the provision of atoms for the solid growth during solidification,which can influence the solidification-characteristics temperatures and the solidification temperature range of Fe-4%Si alloy.