The Anisotropy of Dimensional Change on Sintering of Iron
The Anisotropy of Dimensional Change on Sintering of Iron
复制标题
铁烧结时尺寸变化的各向异性
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
M. Larsson
中科院分区：
文献类型：
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作者：
A. Molinari;E. Torresani;C. Menapace;M. Larsson
用膨胀法研究了铁烧结时尺寸变化的各向异性。沿纵向和横向的尺寸变化不同，平行于压实方向的收缩更为明显。这种现象在烧结早期、低于居里温度的α场中尤其明显。根据收缩动力学模型对结果进行了阐述，以计算沿两个方向的有效扩散系数。这样的有效扩散系数平行于压实方向比垂直于压实方向更高，并且均大于根据文献报道的纯铁活化能计算的扩散系数。这种差异归因于颗粒接触区域冷压实引入的缺陷，这可能会由于位错管机制而增强扩散性，而位错管机制又在低于居里温度时特别强烈。这种解释也可以证明收缩的各向异性是合理的，因为粉末颗粒在单轴冷压实过程中变形不均匀。增强的扩散系数随着时间的推移而增加，并在低于居里点的温度下显示出最大值。参考自激活烧结机制讨论了这一趋势。
The anisotropy of dimensional change on the sintering of iron was investigated by dilatometry. Dimensional changes are different along the longitudinal and transversal directions, and shrinkage is more pronounced parallel to the compaction direction. This phenomenon is particularly pronounced during the early stage of sintering, in the alpha field below the Curie temperature. The results were elaborated according to the kinetics model for shrinkage to calculate an effective diffusion coefficient along the two directions. Such an effective diffusion coefficient is higher parallel to the compaction direction than perpendicular to it, and both are larger than the diffusion coefficient calculated on the basis of the activation energy reported in the literature for pure iron. This discrepancy is attributed to the defectiveness introduced by cold compaction in the particle contact regions, which may enhance diffusivity owing to the dislocation pipe mechanism, which, in turn, is particularly intense below the Curie temperature. This interpretation may also justify anisotropy of shrinkage because the powder particles are inhomogeneously deformed by uniaxial cold compaction. The enhanced diffusion coefficient increases with time and shows a maximum at temperatures below the Curie point. This trend was discussed with reference to the self-activated sintering mechanism.