松永 哲也

Twinnability in face-centered cubic metallic solids is discussed from the viewpoint of wavenumber (k) space. The {111} deformation twinning is one of the main plastic deformation modes enabling the rearrangement of a mirror-symmetry lattice structure across a twin boundary. The crystalline rearrangement around 112¯ in k-space is triggered by changes in the electron density distribution caused by the strain-induced modulation of the electronic band structure around this orientation. This modulation is defined by the twinnability, ε112¯, which reflects the difficulty of the redistribution of electron density around 112¯. This index clarifies that the deformation twinning is suppressed in aluminum (Al) due to its large ε112¯ value. This result rationalizes the disorder between platinum and Al observed in conventional twinnability assessments based on stacking fault energy.

Abstract The effect of alloying elements on the martensitic transformation behavior of Ti–Pd series high-entropy shape memory alloys was investigated. Five compositions incorporating Zr, V, Ni, and Pt were synthesized. DSC analysis revealed that the coherency of the martensitic structure formed by the added elements is crucial for maintaining a high transformation temperature. The findings provide insights into the compositional design of high-temperature shape memory alloys with enhanced thermal stability and functional performance.