Microstructural evolution of a delta containing nickel-base superalloy during heat treatment and isothermal forging

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:621

Article

Mignanelli, P. M.¹  Jones, N. G.¹  Perkins, K. M.²  Hardy, M. C.³  Stone, H. J.¹ 

[1] Univ Cambridge, Dept Mat Sci & Met, Cambridge CB3 0FS, England

[2] Swansea Univ, Inst Struct Mat, Coll Engn, Swansea SA2 8PP, W Glam, Wales

[3] Rolls Royce Plc, Derby DE24 8BJ, England

关键词: Nickel-base superalloys;    Thermomechanical processing;    Electron microscopy;    Microstructure;   

DOI  :  10.1016/j.msea.2014.10.071

来源: Elsevier

【 摘 要 】

The next generation of aerospace gas turbine engines need to operate at higher temperatures and stresses to improve their efficiency and reduce emissions. These operating conditions are beyond the capability of existing nickel-base superalloys, requiring the development of new high temperature materials. Controlling the microstructures of these new materials is key to obtaining the required properties and, therefore, it is critical to understand how these alloys respond to processing and heat treatment. Here, the microstructural evolution of V207M, a new delta containing, nickel-base superalloy, has been investigated following heat treatment and forging. The solvus temperatures of the gamma' and delta phases, determined by differential scanning calorimetry and microscopy, were found to be similar to 985 and similar to 1060 degrees C respectively. Isothermal forging of the alloy was conducted at 1000, 1050 and 1100 degrees C, corresponding to different volume fractions of retained delta. Considerable softening was observed prior to steady state flow when forging at 1000 degrees C, whilst only steady state flow occurred at 1050 and 1100 degrees C. The steady state flow process was believed to be dominated by dynamic recovery in the gamma phase, with an activation energy of 407 kJmol(-1). Samples that exhibited flow softening also showed a significant change in the orientation of the delta precipitates, preferentially aligning normal to the forging axis, and this reorientation was thought to be the cause of the observed flow softening. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license

【 授权许可】

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