Publication Date

11-5-2019

Department

Ames Laboratory; Aerospace Engineering; Mechanical Engineering

Campus Units

Ames Laboratory, Aerospace Engineering, Mechanical Engineering

OSTI ID+

1557776

Report Number

IS-J 10003

DOI

10.1016/j.jallcom.2019.151743

Journal Title

Journal of Alloys and Compounds

Volume Number

808

First Page

151743

Abstract

Minimizing phase transformation (PT) hysteresis is of crucial importance for reliability of shape memory alloy (SMA)-based devices, where the lattice strain/stress caused by thermal hysteresis leads to functional degradation. As a result, understanding structural factors that control PT pathway is critical for development of materials with high reversibility. In this study, two distinct PT mechanisms (from gamma'(1) martensite to beta(1) austenite phase) in Cu–Al–Ni SMAs were revealed by in-situ TEM observation. A growth-dominant conventional PT mechanism shows in the fast quench sample, whereas a nucleation-dominant PT mechanism that suppresses interface propagation and induces high thermal hysteresis displays in the slow quench sample. By characterizing the atomic scale composition and microstructure we discover that slow quenching induces nanoprecipitation that changes chemistry of the matrix alloy, which in turn causes the higher PT hysteresis and temperature, while fast quenching avoids the formation of these nanoprecipitates. Our finding provides valuable insights into the fabrication of SMAs with better reliability.

DOE Contract Number(s)

AC02-07CH11358

Language

en

Department of Energy Subject Categories

36 MATERIALS SCIENCE

Publisher

Iowa State University Digital Repository, Ames IA (United States)

Available for download on Friday, August 07, 2020

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