Unexpected ordering behaviour of Pt₃Al intermetallic precipitates

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• 作者：A. Douglas ; J.H. Neethling ; R. Santamarta ; D. Schryvers ; L.A. Cornish
• 关键词：Intermetallics ; High temperature alloys ; Crystal structure ; Transmission electron microscopy (TEM)
• 刊名：Journal of Alloys and Compounds
• 出版年：2007
• 期刊代码：45_09258388
• 类别：ms
• 出版时间：25 April 2007
• 卷：432
• 期：1-2
• 页码：96-102
• 文件大小：1095 K

摘要

Alloys with a microstructure analogous to the γ/γ′ system of Ni-based superalloys are found in the Pt–Al system. A two-phase microstructure consisting of Pt₃Al precipitates in an fcc (Pt) solid solution was developed to mimic the basic microstructure of Ni-based superalloys. The Pt₃Al precipitates were found to consist of plates that are twin related and have a specific orientation relationship with respect to the matrix. Each plate contains a high density of thin platelets lying perpendicular to the c-direction. The precipitates were expected to crystallise in the D0′c unit cell. However, the experimental results showed that a different ordered structure, based on two modifications of the D0′c unit cell, occurred instead. The observed matrix/precipitate orientation relationship could be justified by misfit considerations.