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Three reversible transformations following the sequence hexagonal close-packed (hcp) → samarium type (Sm-type) → double hexagonal close-packed (dhcp) → distorted face-center cubic (dfcc) are observed at 4.4, 26.7, and 40.2 GPa in the HoDyYGdTb high-entriopy alloy, respectively. The phase transitions are due to the s → d charge transfer during compression.

For a detailed understanding of formation processes of nanocrystals in an amorphous matrix, the study of crystal nucleation and growth processes is of basic interest. In the present study, these processes of α-Fe nanocrystals in amorphous NdFeCoDyB have been studied separately by employing in situ high-temperature x-ray diffraction measurements. A small growth activation energy Eg=(1.8±0.2)eV was determined from the isothermal time dependence of the grain size of α-Fe crystals. By these data together with the nucleation activation energy En=(3.0±0.1)eV, a coarse grain size for the α-Fe phase in the α-Fe∕Nd2Fe14B nanocomposites developed from amorphous NdFeBCoDy can be understood.

Using high sensitivity Moir6 interference technology, the full deformation fields about the stressinduced martensitic transformation P, + ' )' ; of single crystal CuAlNi shape memory alloys (SMAs) are obtained.A straight and sharp interface between martensite and parent phases and its motion during transformation process are clearly observed. The elastic anisotropic properties of the crystal are also quantitatively characterized by this technique. The results show that there is no deformation incompatibility between the two phases, which is different from that of pseudoelasticity where another stress-induced martensitic transformation PI occurs. The present results provide an accurate experimental solution for the phase transformation problem in solids.

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