Development of fine-grained structure and the mechanical properties of nickel-based Superalloy 718

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

卷:555

Article

Lee, Hwa-Teng¹  Hou, Wen-Hsin^1,2 

[1] Natl Cheng Kung Univ, Dept Mech Engn, Tainan 701, Taiwan

[2] Gloria Mat Technol Corp, Ctr Res & Dev, Tainan 730, Taiwan

关键词: Superalloy;    delta phase;    Recrystallization;    Cold forming;    Ultra-fine grains;   

DOI  :  10.1016/j.msea.2012.06.027

来源: Elsevier

【 摘 要 】

Grain refinement is the essential concern in producing Superalloy 718 components. Thermomechanical process as a means of producing fine grain structure has attracted significant attention. However, hot forging with deviations on forging temperature results in significant changes in the microstructure. High volume fractions of delta phase thus produced reduce the amount of niobium available for) gamma formation and consequently lower the strength. In this work, the combination of heavy plastic deformation with subsequent recrystallization was utilized as an effective method to achieve a fine-grained structure. Specimens in this process were first solution treated at high temperatures and then followed by plastic deformation. Subsequent recrystallization caused an immediate precipitation of a fine, uniformly dispersed delta phase from the niobium oversaturated matrix that prohibited grain growth. A fine-grained structure with grain sizes <1 mu m was obtained, smaller than 2.9 mu m that has ever been reported in literature. Tensile test results demonstrate a significant improvement in strength and ductility tested at temperatures of 25 degrees C and 650 degrees C, respectively. (c) 2012 Elsevier B.V. All rights reserved.

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