Creep of a thermally stable nanocrystalline nickel tungsten alloy as measured by high temperature nanoindentation

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

卷:784

Article

Singh, Prince S.¹  Liang, Zhiyuan²  Pharr, George M.²  de Boer, Maarten P.¹ 

[1] Carnegie Mellon Univ, Dept Mech Engn, Pittsburgh, PA 15213 USA

[2] Texas A&M Univ, Dept Mat Sci & Engn, College Stn, TX 77843 USA

关键词: Nanoindentation;    Creep;    High temperature;    Nickel-tungsten alloy;    Thermally stable;   

DOI  :  10.1016/j.msea.2020.139309

来源: Elsevier

【 摘 要 】

The creep behavior of pure nanocrystalline (nc) fcc metals has not been studied above 200 degrees C because the nanoscale grains tend to grow at temperatures moderately above ambient. In this work, we study the creep of nanocrystalline Ni-W (nc Ni-W) up to 450 degrees C, near its thermal stability limit. A nanoindenter with the capability to heat both the specimen and the indenter tip addresses the issue of heat flow and provides more accurate test temperatures when compared to heating only the specimen. Creep experiments are performed on a nc Ni-W film (grain size similar to 15 nm) at 300, 350, 400 and 450 degrees C using the constant load and hold (CLH) method combined with the constant stiffness measurement (CSM) technique in which the peak load is maintained at a constant level. No grain growth occurs even at the highest temperature and highest stress. We conduct an analysis that accounts for the effect of the oscillating loads used in this combined CLH-CSM technique on creep. We find that nc Ni-W exhibits negligible creep at 300 degrees C, and that at 350 degrees C, creep in nc Ni-W is three orders of magnitude smaller than creep in pure nc Ni at 100 degrees C. The creep response of nc Ni-W differs significantly from that predicted by the standard Coble creep model and is attributed to the dislocation-grain boundary interaction.

【 授权许可】

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