Transformation behavior in NiTi-20Hf shape memory alloys – Transformation temperatures and hardness

The microstructure and martensitic transformation behavior of Ni50−xTi50Lax (x = 0.1, 0.3, 0.5, 0.7) shape memory alloys were investigated experimentally. Results show that the microstructure of Ni50−xTi50Lax alloys consists of a near-equiatomic TiNi matrix, LaNi precipitates, and Ti2Ni precipitates. With increasing La content, the amounts of LaNi and Ti2Ni precipitates demonstrate an increasing tendency. The martensitic transformation start temperature increases gradually with increasing La content. The Ni content is mainly responsible for the change in martensite transformation behavior in Ni50−xTi50Lax alloys.

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Effects of Impurities Content (Oxygen, Carbon, Nitrogen) on Microstructure and Phase Transformation Temperatures of Near Equiatomic TiNi Shape Memory Alloys

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:1997522 ◽

1997 ◽

Vol 07 (C5) ◽

pp. C5-143-C5-148 ◽

Cited By ~ 18

Author(s):

P. Olier ◽

F. Barcelo ◽

J. L. Bechade ◽

J. C. Brachet ◽

E. Lefevre ◽

...

Keyword(s):

Phase Transformation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Transformation Temperatures

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Effect of Co-Doping on the Microstructure, Martensitic Transformation Behavior, and Magnetocaloric Effect of Ni-Mn-Sb-Si Ferromagnetic Shape Memory Alloys

Metallurgical and Materials Transactions A ◽

10.1007/s11661-018-4942-3 ◽

2018 ◽

Vol 49 (12) ◽

pp. 6416-6425

Author(s):

Ruochen Zhang ◽

Xuexi Zhang ◽

Mingfang Qian ◽

Lin Geng

Keyword(s):

Martensitic Transformation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Magnetocaloric Effect ◽

Transformation Behavior ◽

Ferromagnetic Shape Memory Alloys ◽

Co Doping ◽

Ferromagnetic Shape Memory

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Effect of Nitrogen Addition on TiNi Shape Memory Alloys

Science of Advanced Materials ◽

10.1166/sam.2020.3806 ◽

2020 ◽

Vol 12 (9) ◽

pp. 1403-1408

Author(s):

Izaz Ur Rehman ◽

Tae-Hyun Nam

Keyword(s):

Mechanical Properties ◽

Shape Memory Alloys ◽

Shape Memory ◽

Tensile Tests ◽

Nitrogen Addition ◽

Ternary Alloys ◽

X Ray Diffraction ◽

Transformation Temperatures ◽

Arc Melting ◽

Type Phase

In present paper we will show how nitrogen effects microstructures, transformation temperatures, and mechanical properties of equiatomic Ti50–Ni50 and Ti-rich Ti51–Ni49 binary shape memory alloys. 0.5 at.% of nitrogen was added to prepare Ti50–Ni49.5–N0.5, and Ti51–Ni48.5–N0.5 (at.%) alloys by arc-melting. Microstructures were investigated by scanning electron microscope (SEM), phase constitutions were investigated by X-ray diffraction (XRD), transformation temperatures were investigated by differential scanning calorimeter (DSC) and mechanical properties were tested by tensile tests. Solutions treated Ti–Ni–N shape memory alloys contain TiNi matrix without nitrogen, Ti2Ni type phase containing a small amount of nitrogen and a new Ti2N type phase containing a small amount of nickel. Compared with Ti50–Ni50 and Ti51–Ni49 binary alloys, the martensitic transformation starts temperatures (Ms) of Ti50–Ni49.5–N0.5 and Ti51–Ni48.5–N0.5 ternary alloys decreased from 63.4 °C to 41.6 °C and from 85.3 °C to 79.4 °C, respectively. By adding N, fracture strain decreased and incomplete superelasticity was observed.

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