The Affect Of Cold Deformation On Hydrogen Absorption Behaivor Of NiTi(Nb) Shape Memory Alloy

NiTi shape memory alloy has good shape memory effect,biocompatibility,wear resistance and high fatigue resistance.so that it is has been widely used in the medical,mechanical control and other fields.Due to Ti is the strong hydrogen absorbing elements,resulting in NiTi shape memory alloy is easy to form a brittle hydride in hydrogen environment,so that it can inhibit the reversible martensite transformation of NiTi shape memory alloy and the effect of shape memory.Meanwhile,the hydrogen absorption behavior of NiTi shape memory alloy has relate to additive elements and processing state.In this paper,.we study the hydrogen absorbing behavior of annealed and cold-drawn NiTi and NiTiNb memory alloy.Using cold drawn to prepare the wires of NiTi shape memory alloy,and using cathode electrolysis method to achieve hydrogen storage.Using SEM,XRD,DSC,tensile tester,hardness tester and other advanced testing methods,Comparative study the effect of the hydrogen-absorbing to the structure and properties of annealed and cold-drawn state NiTi memory alloy.The results showed that the cold deformation promoting the hydrogen-absorbing alloy NiTi memory,After hydrogen absorption,NiTiH compound is formed in the NiTi shape memory alloy,and the NiTi alloy lose shape memory effect.When the hydrogen absorbing sample is heated by 500 ?,the reversible martensitic transformation and shape memory effect restore.The hydrogen absorbing increased the hardness of NiTi shape memory alloy and it become fragility.Hardness values of cold-drawn state hydrogen storage sample is significantly higher than the annealed hydrogen-absorbing sample's.With increasing hydrogen absorbing time,hydrogen storage samples significantly increased center hardness.Because of Nb exist as elemental in NiTiNb memory alloy,and Nb having a large solubility of hydrogen and high hydrogen diffusion coefficient,this paper also study the effect of the hydrogen-absorbing to the structure and properties of annealed and cold-drawn state NiTiNb memory alloy.The study found that cold deformation promoting the hydrogen-absorbing of NiTiNb alloy,comparing with annealed NiTiNb memory alloy samples.After hydrogen absorption,Nb transformed into NbH compound,and when heated to 120 ?,NbH compound transformed into Nb(H)solid solution,in the cooling process,Nb(H)solid solution transformed into NbH compound.Comparing with annealed NiTiNb memory alloy samples,the hardness of cold-drawn NiTiNb samples is higher,and with increasing hydrogen absorbing time,the hardness value of the sample significantly increased.