Allegheny Technologies Inc., Pittsburgh, offers its NiTiNb shape memory alloy for coupling devices that need cryogenic martensite transformation temperatures and also need room temperature storage capability. The effect of low niobium content (3.5 at.%, 4.5 at.%, 5.0 at.%) on the mechanical properties of NiTiNb shape memory alloys has been investigated in detail by differential scanning calorimetry, tensile testing, and scanning electron microscopy.
The Ms temperatures of three kinds of NiTiNb alloys with different amounts of niobium were fixed at about 188 K to eliminate the influence of testing temperature on mechanical function. The experimental results show that with the increase of Nb content, the yield strength increased and the elongation decreased gradually. However, the NiTiNb alloys still keep high elongation.. Furthermore, it has been found that the shape recovery strain of NiTiNb alloy with 5.0 at.% Nb can reach 7.4%. It is believed that NiTiNb alloys with low niobium content can obtain good shape memory characteristics.
