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Heating rate dependence of shape recovery stress in a Ti-49.7Ni alloy
|Ju-young Choi 1, Min-gyun Kim 1, Tae-hyun Nam 1, Eunsoo Choi 2, Baik-soon Cho 3, Young-soo Chung 4|
1. Gyeongsang National University (GSNU), 900 Gazwadong, Jinju 660-701, Korea, South
Effect of heating rate of shape recovery stress of a solution treated Ti-49.7Ni alloy was investigated by means of differential scanning calorimetry(DSC) and tensile tests. Shape recovery stress increased from 80 MPa to 100 MPa with increasing pre-strain from 1 % to 3 %, and then it went down to 80 MPa with increasing pre-strain up to 6 %, which was ascribed to the plastic deformation occurred during loading. Shape recovery stress generated by heating above Af(reversre transformation finish temperature) decreased by cooling and it disappeared at about 313 K, which is very close to Ms(martensitic transformation start temperature). Shape recovery stress measured after 3% pre-strain increased from 100 MPa to 140 MPa with decreasing heating rate from 171 K/min to 1.5 K/min, which was ascribed an adiabatic transformation condition developed by high heating rate. Stress plateau was observed on stress-temperature curves obtained at heating rates higher than 100 K/min. Moreover, shape recovery stress increased from 140 MPa to 308 MPa with increasing heating temperature from 363 K to 453 K which is very higher than Af measured from DSC(348 K). The increase in shape recovery stress above Af was attributed to the increase in Af by stress applied on the specimen.
Presentation: Poster at E-MRS Fall Meeting 2007, Symposium E, by Tae-hyun Nam
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-03 00:57 Revised: 2009-06-07 00:44