Crack propagation mechanisms of an aged nickel-titanium-hafnium shape memory alloy

SCRIPTA MATERIALIA

卷:159

Article

Amin-Ahmadi, Behnam¹  Noebe, Ronald D.²  Stebner, Aaron P.¹ 

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

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

关键词: Shape memory alloys (SMA);    Martensitic phase transformation;    Twinning;    Crack propagation;    Transmission electron microscopy (TEM);   

DOI  :  10.1016/j.scriptamat.2018.09.019

来源: Elsevier

【 摘 要 】

Mechanisms of crack propagation in a NiTiHf sample were studied from post-mortem microstructure characterizations about cracks. Transmission electron microscopy (TEM) analysis showed that a crack propagated within a martensite band along < 011 > type II twin planes. The crack was observed to switch between different twin planes to avoid precipitates. The crack tip terminated outside of the martensite band, within surrounding austenite. Amorphization of crack edges in both austenite and martensite was also detected, together with Ni enrichment High-resolution TEM examination of crack tip inside the austenite phase also confirmed the formation of martensite nanocrystals embedded in the amorphous regions. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

【 授权许可】

Free