An introduction to tetragonal (t) → monoclinic (m) martensitic transformation in zirconia containing ceramics, especially tetragonal zirconia polycrystalline (TZP) was presented. Thermodynamics, crystallographics and kinetics of t → m martensitic transformation in TZP were emphasized. Transformation toughening and shape memory effect (SME) associated with t → m martensitic transformation in the TZP were reviewed. Perspective of future challenges was briefly mentioned at the end.

Martensitic transformation in zirconia containing ceramics and its applications

Re-investigation of phase equilibria in the system Al-Cu and structural analysis of the high-temperature phase η1-Al1-δCu.

Energy balance of thermoelastic martensite transformation under stress

Thermomechanical training behavior and its dynamic mechanical analysis in an Fe-Mn-Si shape memory alloy

On the basis of classical nucleation theory of martensitic transformation (MT), the effect of internal stress on autocatalytic nucleation of MT is quantitatively described. The complex stress field pictures outside a formed martensitic plate are first calculated through Eshelby’s theory, and then the interaction energies between the martensitic plate and embryos with 24 possible variants can be further obtained. Based on the calculation of interaction energy, the effect of internal stress on autocatalytic nucleation of MT and morphological characteristics of martensite are explained. In this investigation, two kinds of alloys—non-thermoelastic materials (e.g., Fe-30Ni) and thermoelastic materials (e.g., Cu-46.6Zn)—are studied, and their difference in autocatalytic nucleation and morphological characteristics of martensite are indicated.

Effect of internal stress on autocatalytic nucleation of martensitic transformation

The phase diagram of CuAl system has been fully utilized to derive several thermodynamic parameters of CuAl alloys on the basis of the regular solution model. A statistical method has also been used to deal with α → α′ and β → β′ ordering transitions accompanying the martensitic transformation in CuAl alloys. The equilibrium temperatures T 0 ∗ and T 0 , as well as Ms temperature have then been calculated theoretically in CuAl alloys with various compositions, and the Ms obtained are in good agreement with the experimental ones. The calculated results also show that the equilibrium temperature of the ordered α′ and β′ phases, T0, is higher than that of the disordered α and β phases, T 0 ∗ .

Thermodynamics of the martensitic transformation in CuAl alloys

The driving forces for various possible reactions within the bainitic transformation temperature range of Cu 40 at.% Zn alloy have been calculated. The results show that because of the occurrence of β→β′ ordering transition within the temperature range, the driving forces ΔG β ′→ α ′ and ΔG β ′→ β ′+ α increase inversely with decreasing temperature, with ΔG β ′→ α ′ > 0 and ΔG β ′→ β ′+ α T 0 of the two phases β′ and α′ is far below the experimental B s for alloys of various compositions. Therefore, the bainitic transformation in CuZn alloys can only proceed as that of diffusional reaction β ′→ β 1 ′+ α .

X.W. Zhou

Papers

Thermodynamics of the martensitic transformation in CuAl alloys

Thermodynamics of the bainitic transformation in a CuZnAl alloy