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Title: Microstructure–property relationships in a high-strength 51Ni–29Ti–20Hf shape memory alloy

NiTiHf alloys exhibit remarkable shape memory and pseudoelastic properties that are of fundamental interest to a growing number of industries. In this study, differential scanning calorimetry and isothermal compression tests have revealed that the 51Ni–29Ti–20Hf alloy has useful shape memory properties that include a wide range of transformation temperatures as well as highly stable pseudoelastic behavior. These properties are governed by short-term aging conditions, which may be tailored to control transformation temperatures while giving rise to exceptionally high austenite yield strengths which aid transformation stability. The yield strength of the austenite phase can reach 2.1 GPa by aging for 3hrs at 500°C, while aging for 3hrs at 700°C produced an alloy with an austenite finish temperature (A f ) of 146°C. High-resolution scanning transmission electron microscopy has revealed a new precipitate phase, H-phase, under the homogenized and extruded condition and the aged 3 hrs at 500°C condition, but only the previously identified H-phase precipitate was observed after aging at temperatures of 600°C and 700°C for 3 hrs. Finally, dislocation analysis indicated that plastic deformation of the austenite phase occurred by <100> type slip, similar to that observed in binary NiTi.
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. The Ohio State Univ., Columbus, OH (United States)
  3. Glenn Research Center, Cleveland, OH (United States)
Publication Date:
OSTI Identifier:
1221618
Report Number(s):
LA-UR--15-26868
Journal ID: ISSN 0022-2461; PII: 9400
Grant/Contract Number:
SC0001258; AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Journal of Materials Science
Additional Journal Information:
Journal Name: Journal of Materials Science; Journal ID: ISSN 0022-2461
Publisher:
Springer
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE