How Does Substitution in NiTi Lattice Affect Transformation Temperatures?

[scott_alexsk]

Hello,

I was curious as to what you think of the paper below. This concerns the effects of substitution in a NiTi lattice on the transformation temperatures. The author seems to draw from this study, that since Nickel has comparatively localized electrons, the increase in temperature stabilizes Ni bonds with neighboring atoms. Since the Ni and Ti atoms are packed in a ordered fashion in the B2 structure, the weakening of Ni bonds with a decrease in temperature, results essentially in the shearing of a plane of atoms, changing the crystal structure from B2 (CsCl) to Bl9' (distorted face centered). Essentially the bonds between Ti atoms in the lattice remain strong, and with the coresponding weakening of the Ni bonds, the Ti atoms come closer together and the Ni are pushed apart. Consequently subsitituting atoms with varying electronegativities alters the transformation temperatures, expected from this theory.
Is this explanation for the transformation in memory alloys such as nitinol, mainstream? I mean is this a widely excepted theory, or is it disputable to your knowledge? Also if you notice any misconceptions I have, would you please point them out. Any additional papers you may know concerning the topic would be welcomed too.

http://www.public.iastate.edu/~svetinol/papers/articleicomat.pdf"

Thanks,
-scott

 

[Aaron Barnard]

In general, the explanation you have provided in your question is an accurate description of the transformation process that occurs in NiTi-based alloys (commonly known as Nitinol). It is widely accepted that the transformation temperatures can be altered through substitution of different atoms with varying electronegativities. This phenomenon is attributed to a change in the stability of the bonds between Ni and Ti atoms due to a difference in their localized electron density.

The paper you provided does indeed support this explanation, as it discusses the effects of substitution in NiTi lattices on the transformation temperatures. It also states that substitution of Ni with other elements can result in changes to the crystal structure from B2 (CsCl) to B19' (distorted face centered), which is consistent with the description you provided in your question.

Overall, the theory you have described is widely accepted among scientists who study these materials. There may be some slight disagreements or modifications to the theory, but the overall explanation is generally accepted. If you are interested in learning more about this topic, you may want to look into papers related to the thermodynamics of NiTi alloys, as well as papers that discuss the effects of substitution on the transformation temperatures.

 

[charng]

Hello Scott,

Thank you for sharing this interesting paper on the effects of substitution in a NiTi lattice on transformation temperatures. The author's theory that the increase in temperature stabilizes Ni bonds with neighboring atoms, resulting in a change in crystal structure from B2 to Bl9', seems plausible based on known principles of crystal structure and bonding. However, this is just one proposed explanation and may not be the only factor influencing the transformation in memory alloys like nitinol.

The concept of localized electrons in Nickel and its effect on bonding is well-established in the scientific community. However, the specific mechanism proposed in this paper may still be open to debate and further research. it is always important to critically evaluate and question theories, even if they are widely accepted. This helps to advance our understanding and refine existing theories.

I am not aware of any major disputes or controversies surrounding this theory, but it is always possible that new evidence or alternative explanations may emerge in the future. As for additional papers on this topic, a quick search on Google Scholar or other academic databases may yield more relevant studies. I hope this helps and thank you again for sharing this interesting paper.