Solidification paths and carbide morphologies in melt-processed MoSi2-SiC In Situ composites
Solidification paths and carbide morphologies in melt-processed MoSi2-SiC In Situ composites
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熔融加工 MoSi2-SiC 原位复合材料的凝固路径和碳化物形态
DOI：
10.1007/s11661-997-0119-1
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
C. Levi
中科院分区：
文献类型：
--
作者：
D. Tilly;J. Löfvander;C. Levi
研究了熔融法制备的MoSi2-SiCin复合材料的显微组织演变。通过热力学建模、凝固微观组织分析和凝固过程中热历史的测量，对现有的液相线投影进行了评估。结果表明，在∼为2At时，存在准二元MoSi2-SiC共晶。C和2283K，而不是8at。PCT C和2173 K，如之前报道的那样。随后的L+MoSi2+碳化硅单变线几乎平行于SiMoSi2二元线，终止于L↔Si+MoSi2+碳化硅三元共晶线，计算温度为1.5Mo-0.84C(at.Pct)和∼1670K。沿准二元等值线凝固可产生的最大碳化硅含量为∼37volpt，其中∼35volpt为初级生长。凝固组织分析表明，碳化硅以立方β多型结构(B3)生长，而MoSi2以四方C11b结构生长。初生碳化硅可能以等轴状颗粒、片状和漏斗状晶体的形式生长。与MoSi2的耦合生长形成了薄带、片状和针状的碳化硅。碳化硅晶体的晶面为{111}和{002}两种类型，与周期键链分析相一致。主要的片状形貌是由于一种类似于在Si和Ge中观察到的重入孪晶机制而形成的。
The present investigation was undertaken to elucidate the microstructural evolution of MoSi2-SiCin situcomposites produced by melt processing. An assessment of the existing liquidus projection was performed by a combination of thermodynamic modeling, analysis of solidification microstructures, and measurements of the thermal history during solidification. Results show that the quasibinary MoSi2-SiC eutectic occurs at ∼2 at. pct C and 2283 K, rather than 8 at. pct C and 2173 K, as previously reported. The ensuing L+MoSi2+SiC monovariant line runs almost parallel to the SiMoSi2binary and terminates at a ternary L ↔ Si+MoSi2+SiC eutectic calculated at 1.5Mo-0.84C (at. pct) and ∼1670 K. The maximum amount of SiC that may be produced by solidification along the quasibinary isopleth is ∼37 vol pct, of which ∼35 vol pct grows as primary. Analysis of solidification microstructures shows SiC grows with the cubicβpolytype structure (B3), while MoSi2grows with the tetragonal C11bstructure. Primary SiC may grow as equiaxed particles, platelets, and hopper crystals. Coupled growth with MoSi2leads to SiC in the shape of thin ribbons, sheets, and needles. The facets of the SiC crystals were identified to be of the {111} and {002} type, in agreement with the periodic bond chain analysis. The predominant platelike morphology was shown to develop due to a re-entrant twin mechanism similar to that observed in Si and Ge.