Evidence of relaxation has been observed in ferromagnetic Ni-Mn-Ga single crystals. The relaxation may be explained by a change in symmetry-conforming short-range ordering according to Ren and Otsuka in this off-stoichimetric ordered alloy. Martensite stabilization has also been found after martensite ageing.

The thermoelastic behavior and crystallography of the tetragonal (t)→ monoclinic(m) martensitic transformation in Ce-Y-TZP ceramics are investigated by means of in situ transmission electron microscopy (TEM) and Wechsler-Lieberman-Read phenomenological theory. In situ TEM observations show that in Ce-Y-TZP the t/m interface can move freely with the change of thermal stress supplied by the beam illumination, whereas this is not found in thermal cycles. Based on the features of reversibility of interface motion, large thermal hysteresis and high critical driving force for Ce-Y-TZP, the t→ m transformation is suggested as a semi-thermoelastic one. The habit plane and the lattice correspondence are determined as (130)t and [001]t//[010]m, which is in agreement with the calculated results of the phenomenological theory.

Effects of 1 T external magnetic field on the transformation strains and resistivity changes associated with martensitic transformation in Ni2MnGa single crystals have been investigated by simultaneously monitoring the variations in strain and electrical resistivity with temperature. The results show that the strains on transforming from austenite to martensite are larger than that for the reverse transformation when the transformation takes place under 1 T external magnetic field. The reason for larger transformation strain mainly arises from the growth of favorable martensitic twin variants under external magnetic field rather than the magnetic field effect on the shift of martensitic transformation temperatures.

Internal friction and the elastic modulus of Ni-Mn-Ga single crystals have been simultaneously measured as a function of the temperature during cooling and heating at 3

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.