Coherency strains of H-phase precipitates and their influence on functional properties of nickel-titanium-hafnium shape memory alloys

SCRIPTA MATERIALIA

卷:147

Article

Amin-Ahmadi, Behnam¹  Pauza, Joseph G.¹  Shamimi, Ali²  Duerig, Tom W.²  Noebe, Ronald D.³  Stebner, Aaron P.¹ 

[1] Colorado Sch Mines, Mech Engn, Golden, CO 80401 USA

[2] Confluent Med Technol, Fremont, CA 94539 USA

[3] NASA, Glenn Res Ctr, Mat & Struct Div, Cleveland, OH 44135 USA

关键词: Aging;    Transmission electron microscopy (TEM);    Geometrical phase analysis (GPA);    Precipitation;    Shape memory alloys (SMA);   

DOI  :  10.1016/j.scriptamat.2018.01.005

来源: Elsevier

【 摘 要 】

A Ni(50.3)Ti(41.7)Hfs alloy was studied after two-step aging treatments consisting of 300 degrees C for 12 h followed by 550 degrees C for different times. An anomalous change in transformation temperatures was observed as the second aging time was increased from 7.5 to 13.5 h. Initially with increased aging time (0.5-7.5 h) at 550 degrees C, coherency strain fields about H-phase precipitates increased. The corresponding backstress favored martensite formation, hence an increase in transformation temperatures. However, a point was eventually reached where misfit dislocations relaxed those strain fields and the effect was reduced, resulting in a decrease in transformation temperatures. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

【 授权许可】

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