Investigation of Transformation Temperatures, Microstructure and Shape Memory Properties of NiTi, NiTiZr and NiTiHf Alloys

P. Olier; J.C. Brachet; J.L. Bechade; C. Foucher; G. Guénin

doi:10.1051/jp4/199558741

Numéro		J. Phys. IV France Volume 05, Numéro C8, Décembre 1995 International Conference on Martensitic Transformations – ICOMAT 95


Page(s)		C8-741 - C8-746
DOI		https://doi.org/10.1051/jp4/199558741
Publié en ligne		14 juillet 2014

J. Phys. IV France 05 (1995) C8-741–C8-746

Investigation of Transformation Temperatures, Microstructure and Shape Memory Properties of NiTi, NiTiZr and NiTiHf Alloys

P. Olier¹^,2, J.C. Brachet², J.L. Bechade², C. Foucher² and G. Guénin³

¹ CEA/INSTN/SEPEM, C.E. de Saclay, 91191 Gif sur Yvette, France
² CEA/CEREM/DECM/SRMA, C.E. de Saclay, 91191 Gif sur Yvette, France
³ GEMPPM/INSA de Lyon, 69621 Villeurbanne cedex, France

Abstract

The influence of zirconium and hafnium additions in substitution to titanium, is investigated on TiNi shape memory alloy. Microstructural and thermomechanical studies are conducted on an arc-melted Ti₃₈Ni₅₀Hf₁₂ alloy. Results are compared with those of an equiatomic TiNi.

We confirm the increase of the phase transformation temperatures due to the additions of Zr and Hf. The presence of oxides in the cast alloy was detected. The lattice parameter is measured from a residue of electroextraction. It was found that a₀=1,1547±0,0001nm. A stoichiometry of (Ti, Hf) ₄Ni₂ O_x (with x≤1) is suggested.

It appears that this ternary alloy exhibit an improved shape recovery when it is pre-strained in austenite state (for M_s < T < A_s) . In this case it displays 100% of recovery for 4% of deformation.