[工程科技]Volume Effect in the Landau Theory of Martensitic Phase Transitions in Cubic Crystals.pdfVIP

Submitted to Phys. Rev. B Volume Effect in the Landau Theory of Martensitic Phase Transitions in Cubic Crystals 4 M.A.Fradkin† 9 9 Institute of Crystallography, Russian Academy of Sciences 1 n 59 Leninsky prospect, Moscow, 117333, Russia u J (June 5, 1994) 7 2 v 0 3 Abstract 0 6 0 4 An effect of the volume change upon proper ferroelastic (martensitic) phase 9 / transitions in cubic crystals is considered. Corresponding terms in the t a m Ginzburg-Landau expansion of the Gibbs free energy are analyzed for the - d n first- as well as second-order phase transitions from cubic to tetragonal lat- o c tice under the action of uniaxial and hydrostatic pressure. The pressure effect : v i on the critical temperature as well as on the phase transition anomalies of X r a isothermal compressibility and linear thermal expansion coefficient are stud- ied and recent experimental data on thermal expansion anomalies in V Si, 3 In-Tl and Ni-Al are discussed. The non-linearity of thermal expansion leads to the special relation between the shear strain and volume change as a re- sult of the elastic energy minimization. This phenomenon can provide the transformation from FCC lattice to BCC one, observed in the iron alloys. PACS: 05