Ordering Transformation and Age Hardening in a Ni-Cr-W Superalloy

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• 作者：Xiangyu Gao ; Rui Hu ; Xiaolin Li ; Gongliao Luo…
• 刊名：Metallurgical and Materials Transactions A
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：47
• 期：12
• 页码：5907-5917
• 全文大小：3,257 KB
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Chemistry
  Materials Science
  Metallic Materials
  Structural Materials
  Physical Chemistry
  Ceramics,Glass,Composites,Natural Materials
  
• 出版者：Springer Boston
• ISSN：1543-1940
• 卷排序：47

文摘

The microstructural changes occurring in a Ni-Cr-W superalloy during prolonged exposure to proper temperature have been investigated using transmission electron microscopy. It is demonstrated that nanometer-sized C11_b (Pt₂Mo-type) and DO₂₂ superlattices can precipitate in the Ni-Cr-W alloy by means of a simple aging treatment at temperatures varying in the range of 773 K to 973 K (500 °C to 700 °C). The mechanism of transformation to long-range order has been revealed to accord with continuous mode based on transmission electron microscopy results and variation trend in Vickers microhardness. No signs of overaging and coarsening of C11_b and DO₂₂ phases with further aging have been found, which indicates that both of them have a high-thermal stability. The orientation relationships and interfaces between C11_b/DO₂₂ precipitates and Ni-based matrix have been investigated by high-resolution transmission electron microscopy, and the results reveal that the interfaces between C11_b/DO₂₂ precipitates and surrounding matrix are coherent at the atomic scale. Because of the high-density nanometer-sized C11_b/DO₂₂ precipitates, the microhardness of the alloy is improved remarkably.