J Mater Sci Technol ›› 2009, Vol. 25 ›› Issue (02): 215-218.

• Articles • Previous Articles     Next Articles

A Comparative Study of Elastic Constants of NiTi and NiAl Alloys from First-Principle Calculations

Jianmin Lu, Qingmiao Hu and Rui Yang   

  • Received:2007-11-02 Revised:2007-12-27 Online:2009-03-28 Published:2009-10-10
  • Contact: Jianmin Lu

Abstract:

To investigate the origin of the strong dependence of martensitic transformation temperature on composition, the elastic properties of high temperature B2 phases of both NiTi and NiAl were calculated by a first-principle method, the exact-muffin orbital method within coherent potential approximation. In the composition range of 50-56 at. pct Ni of NiTi and 60-70 at. pct Ni of NiAl in which martensitic transformation occurs, non-basal-plane shear modulus c44 increases with increasing Ni content, while basal-plane shear modulus c′ decreases. In the above composition ranges however the transformation temperature of NiAl increases with increasing Ni content while that of NiTi decreases from experimental observation. The softening of c′ is experimentally observed only in NiAl, and the decrease of c′ with increasing Ni content is responsible for the increase of transformation temperature. The result of the present work demonstrates that, besides c′, c44 also influences the martensitic transformation of NiTi and plays quite important a role.

Key words: NiTi, NiAl, Elastic constant, First-principle calculation