Effect of sintering methods and cobalt addition on the shape memory properties of porous TiNi-based alloy
Abstract
The changes of shape memory characteristics and properties of the porous sintered TiNi-based alloy are possible by a choice of the sintering methods or use of cobalt doping additive, as the present investigation has showed. The comparative analysis of the temperature dependences of electric resistance and macrodeformation both alloys, obtained by reaction and diffusion sintering was conducted. Diffusion-sintered alloy have showed high shape memory parameters and a more uniform passing of martensitic transformations. This is connected with a larger fraction of TiNi phase (about 90 vol.%) after diffusion sintering. It was found that the martensitic transformation characteristics and reversibility of martensitic strain in the porous nickelid titanium depend on level of intrinsic stresses in the TiNi phase and stresses caused by Co impurity. The addition to 1.0 at.% Co decreases the internal stresses in the TiNi phase, and more than 1.0 at.% Co increases their due to the effect of precipitation hardening of the alloy.
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