Martensite structure in Ti–Ni–Hf–Cu quaternary alloy ribbons containing (Ti,Hf) 2Ni precipitates

• Published in: Acta materialia Vol. 58; no. 10; pp. 3751 - 3763
• Main Authors: Meng, X.L., Cai, W., Fu, Y.D., Zhang, J.X., Zhao, L.C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-06-2010; Elsevier
• Subjects: Annealing; Applied sciences; Boundaries; Exact sciences and technology; Martensite; Metals. Metallurgy; Microstructure; Precipitates; Precipitation; Ribbons; Shape memory effect; Superelasticity; Ti–Ni–Hf–Cu alloy; Transmission electron microscopy; Transmission electron microscopy; Ti–Ni–Hf–Cu alloy; Microstructure; Martensite; Precipitates; Precipitation; Precipitate; Ti―Ni―Hf―Cu alloy
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2010.03.015

The martensite structure in a Ti
36Ni
44Hf
15Cu
5 ribbon annealed at different temperatures is investigated. When the annealing temperature is <873
K, spherical (Ti,Hf)
2Ni particles 20–40
nm in diameter precipitate in the grain interior. Transmission electron microscopy analysis shows that (0
0
1) compound twins are dominant in the ribbon containing homogeneously distributed (Ti,Hf)
2Ni precipitates. When the annealing temperature is 773
K, the boundaries between the martensite domains with the (0
0
1) twins are blurry and vague. When the annealing temperature is 873
K, four types of boundaries among the martensite domains are found: {1
1
1}, (0
0
1)//{1
1
1}, {1
1
3} and (1
1
0)//{1
1
3} types. When the annealing temperature is 973
K, the (0
1
1) twins become dominant, and the martensite variants show mainly spear-like and mosaic-like morphologies. However, martensite domains with (0
0
1) twins also exist around the coarse (Ti,Hf)
2Ni precipitates. Fine (Ti,Hf)
2Ni precipitates should be responsible for the improvement in shape memory effect and the superelasticity of Ti–Ni–Hf–Cu ribbons.