Microstructural transitions during containerless processing of undercooled Fe-Ni alloys
Microstructural transitions during containerless processing of undercooled Fe-Ni alloys
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DOI：
10.1007/bf02665066
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发表时间：
1992-04
期刊：
影响因子：
--
通讯作者：
Dan Thoma;J. Perepezko
中科院分区：
文献类型：
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作者：
Dan Thoma;J. Perepezko
与凝固在过冷Fe-Ni合金的显微组织的发展已在不同的研究报告遵循各种途径，与存在明显的差异作为一个功能的样品尺寸和加工条件。为了确定可能的层次结构的微观结构的途径和过渡，在过冷Fe-Ni合金的微观结构演变进行了系统的评价，均匀处理的样品，覆盖7个数量级的体积。在适当的过冷度水平下，交替凝固路径成为可能，并且亚稳态产品结构可以由竞争性凝固动力学的操作产生。对于热历史评估，应用热流分析并用大的Fe-Ni合金颗粒（1至3 mm）进行测试以评估过冷潜力。在相同的成分和工艺条件下，研究了具有大液体过冷度的合金粉末（10至150 µm），以评估凝固动力学和微观结构演变，包括面心立方（fcc）/体心立方（bcc）相选择和保留的亚稳bcc相的热稳定性。在无容器的凝固过程中的样品尺寸和成分的控制变化的微观结构转变的识别被用来开发一个微观结构图，描绘制度的结构演变，并提供了一个统一的分析，在Fe-Ni系统的实验观察。
The microstructural development associated with solidification in undercooled Fe-Ni alloys has been reported in different studies to follow various pathways, with apparent dissimilarities existing as a function of sample size and processing conditions. In order to identify the possible hierarchy of microstructural pathways and transitions, a systematic evaluation of the microstructural evolution in undercooled Fe-Ni alloys was performed on uniformly processed samples covering seven orders of magnitude in volume. At appropriate undercooling levels, alternate solidification pathways become thermodynamically possible and metastable product structures can result from the operation of competitive solidification kinetics. For thermal history evaluation, a heat flow analysis was applied and tested with large Fe-Ni alloy particles (1 to 3 mm) to assess undercooling potential. Alloy powders (10 to 150 µm), with large liquid undercoolings, were studied under the same composition and processing conditions to evaluate the solidification kinetics and microstructural evolution, including face-centered cubic (fcc)/body centered cubic (bcc) phase selection and the thermal stability of a retained metastable bcc phase. The identification of microstructural transitions with controlled variations in sample size and composition during containerless solidification processing was used to develop a microstructure map which delineates regimes of structural evolutions and provides a unified analysis of experimental observations in the Fe-Ni system.