Direct Evidence for Local Symmetry Breaking during a Strain Glass Transition

作者：Zhou, Yumei; Xue, Dezhen^*; Tian, Ya; Ding, Xiangdong; Guo, Shengwu; Otsuka, Kazuhiro; Sun, Jun; Ren, Xiaobing

来源：Physical Review Letters, 2014, 112(2): 025701.

DOI：10.1103/PhysRevLett.112.025701

• TRANSMISSION ELECTRON-MICROSCOPY
• BOUNDARY-LIKE STRUCTURE
• SHAPE-MEMORY ALLOY
• ANTIPHASE BOUNDARY
• PREMARTENSITIC MICROSTRUCTURES
• MARTENSITIC-TRANSFORMATION
• FERROELASTIC SYSTEMS
• NEUTRON-SCATTERING
• BETA-2 PHASE
• BEHAVIOR

Strain glass transition is a unique nanoscale displacive transition with local symmetry breaking while maintaining the macroscopic symmetry or average structure unchanged. It usually occurs in the "non-martensitic" composition range of a martensitic system. So far, only indirect evidence exists for such a transition, essentially from macroscopic measurements and low-resolution transmission electron microscopy observations, and there is a lack of direct evidence for the speculated local symmetry breaking and the sluggish nature of the glass transition. In this Letter we report in situ high-resolution transmission electron microscopy observations on a Ti-50(Pd41Cr9) strain glass alloy and direct evidence for these key issues. Our results show that at temperatures well above the strain glass transition temperature (T-g), the lattice is essentially an undistorted B2 structure. With approaching T-g, the local symmetry breaking gradually occurs with the formation and growth of nanomartensite clusters with a combined stacking period of three and four plane intervals, but the average structure measured by x-ray diffraction remains B2. These nanomartensite clusters become finally frozen below T-g. Our results provide not only a microscopic basis for the macroscopic properties of strain glass, but also new insights into a range of possible applications of this unique class of materials.

• 出版日期2014-1-16
• 单位西安交通大学