日本金属学会誌

J. Japan Inst. Metals, Vol. 54, No. 2 (1990),
pp. 214-223

Possibility of Manufacturing of NiTi Intermetallic Compound by Combustion Synthesis

Minoru Otaguchi1, Yoshinari Kaieda1, Nobutaka Oguro1 Shuji Shite2 and Tadashi Oie2

1National Research Institute for Metals, Tokyo
2Kyoritsu Ceramic Materials Co., Ltd., Nagoya

Abstract:

NiTi shape memory alloy is usually produced by the process including high frequency induction vacuum melting. The transformation temperature of the NiTi shape memory alloy is said difficult to be controlled precisely because the martensitic transformation temperature is changed by 10 K due to the change of 0.1 mass% of Ni content. In the present paper, it is reported that the NiTi intermetallic compound is synthesized by the combustion synthesis method, which is a newly developed manufacturing process, by controlling the content of Ni and Ti elemental powders. In the process, Ni and Ti powders are weighed and mixed to 50 at% of Ni by the dry ball mill. The mixed powder is filled in the graphite crucible and the top of the powder is ignited by heating with tungsten heater in vacuum (10-4 Pa) or argon gas atmosphere. Then the combustion synthesis of NiTi is self-propagated to the end of the powder. The synthesized NiTi is then sintered by hot isostatic press (HIP). The HIP'ped NiTi is plastically worked to the plate and wire. The ignition of the combustion synthesis is successful in high vacuum and argon gas atmosphere from room temperature to 873 K, and the chemical reaction is completely propagated. 100% NiTi intermetallic compound is observed by X-ray diffraction analysis in the combustion synthesized NiTi ignited at any temperature in the present experiment. As combustion-synthesized NiTi ingot is porous and the relative density is 50-60%, but after HIP'ping the relative density increased to 100%. The HIP'ped ingot is plasticauy worked with hot rolling, hot bar-rolling, hot and cold rotary-swaging and cold-drawing. When the oxygen content of the synthesized NiTi is about 0.5%, the 0.5 mm diameter wire is obtained. However, when the oxygen content is under 0.07%, a 0.09 mm diameter wire is achieved. The wire has the shape memory effect and the shape memory temperature of it is about 370 K.


(Received 1988/10/24)

Keywords:

elemental powder, combustion synthesis, intermetallic compound, NiTi alloy, shape memory alloy, super-elastic alloy


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