Speaker
Description
Operation conditions in microelectronics, sustainable mobility, and space exploration increasingly demand mastering thermal expansion due to large temperature swings and stringent dimensional tolerances. However, customizing thermal expansion of conventional metallic materials is extremely difficult. Their expansion behaviour is largely unaffected by alloying, and their lattice expansion typically shows minimal or no crystallographic anisotropy, limiting the usefulness of texture engineering. Even Fe–Ni Invar alloys, despite their widespread use, offer only a narrow window of low yet still positive expansion coefficients. While some materials with negative thermal expansion are known, they are predominantly non-metallic, often brittle, and difficult to texture.
Recently, several research groups have introduced a new materials design principle that enables broad tailoring of thermal expansion in a large class of alloys through straightforward thermomechanical processing. The key feature shared by these materials are martensitic phases with strongly anisotropic lattice expansion. For a single alloy chemistry, the macroscopic polycrystal thermal expansion can be adjusted across a wide range by generating crystallographic texture via appropriate deformation routes. Among such systems, Ti alloys forming orthorhombic α'' phases stand out due to their exceptionally large contraction and expansion rates, excellent deformability, and strong composition-dependent expansion behaviour.
This presentation will review foundational findings and recent advances from the past two decades and provide an overview of current research directions. A new integrated strategy developed by our group—combining control of phase constitution, texture, and phase fraction—significantly enlarges the available design space, offering ample prospects for future exploration and technological innovation.