Thermoelastic Properties of Super High Temperature Ru-Ta Shape Memory Alloy
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Thermoelastic Properties of Super High Temperature Ru-Ta Shape Memory Alloy Y.Furuya 1 and H.Zhirong2 Department of Intelligent Machines and System Engineering, Hirosaki University, Hirosaki 036-8152, Japan 2 Visiting Professor of Hirosaki University, and at present, Department of Material Science and Engineering, Shaanxi Institute of Technology, Shaanxi,China
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ABSTRACT Equiatomic Ru-Ta alloy can show a thermoelastic phase transformation at super high temperatures above 1000 . The temperature of shape memory effect of this alloy seems to be remarkably higher by two times than those of the formerly reported high temperature NiMnAl alloy and it seems very interesting as one of the new high temperature SMAs, however, detailed thermoelastic properties of Ru-Ta system alloy have not been clarified. The present paper investigates the basic material properties of Ru-Ta alloy, i.e. each transformation temperature, temperature hysteresis range, heat absorption by DSC measurement and metallurgical compounds by X-ray diffraction that depend on alloy composition by changing the Ru content from 46-54at%. Effect of heat treatment at solution temperature and aging temperature on thermoelastic phase transformation points is investigated and the thermal cyclic stability is also studied for engineering applications as high temperature actuator/sensor materials.
INTRODUCTION It is desirable to develop high temperature actuator/sensor materials which can respond to especially in the fields of controlling parts in electric changes of temperature above 400~500 power plants, chemical reaction plants and fire accident prevention etc.. As for a candidate of high temperature potential actuator/sensor materials, piezoelectric ceramics (PZT) and/or magnetostrictive materials has been studied, however, these are inevitably restricted and impossible for application temperatures above 300~400 due to their low Curie points. On the other hand, some shape memory alloys(SMAs) have their phase transformation and recovery temperature above 400 ,i.e. the NiAlMn alloy system has its inverse transformation, Af point near 600 . Moreover, it was found by R.Fonda 1 and Y.Furuya 2 that the equiatomic Ru-Ta alloy can as shown in show a thermoelastic phase transformation at super high temperatures above 1000 Fig.1. This Af value associated with the shape memory effect is remarkably higher, by two times , than that of the formerly reported high temperature NiMnAl alloy. Therefore, Ru-based shape memory alloys will be applicable to ultra-high temperature turbine blades for developing higher efficiency jet engines and super heat-resistance components such as the tip material of the wings of aerospace vehicle due to the better ductility toughness and mechanical strength than ceramics at super high temperature region over 1000 . These features seem to be very attractive, however, detailed thermoelastic properties of Ru-Ta system alloy have not been clarified. In the present paper, we investigate the basic material properties of Ru-Ta alloy, each transformation t
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