About this Abstract |
| Meeting |
MS&T25: Materials Science & Technology
|
| Symposium
|
Microstructural Control in Materials Processing: Role of Phase Transformation Pathways
|
| Presentation Title |
Cold-Rolling-Induced Novel Sub-Grain Structures in NiTi SMAs Enabling Unique Transformation Pathways and Mechanical Behavior |
| Author(s) |
Qianglong Liang, Dong Wang, Michael Mills, Yunzhi Wang |
| On-Site Speaker (Planned) |
Yunzhi Wang |
| Abstract Scope |
Plastic deformation significantly affects the transformation behavior and properties of ferroelastic materials like TiNi shape memory alloys (SMAs). This study explores the formation of a unique herringbone-like sub-grain structure with twin boundaries in the B2 phase of cold-rolled TiNi50.8 (at.%) and its effect on martensitic transformation and superelasticity. EBSD analysis reveals abundant, misoriented sub-grains and distinctive banded and herringbone features, all exhibiting coincident site lattice (CSL) boundaries. TEM confirms B2 twin relationships associated with CSL Σ boundaries, while HAADF imaging shows B19′ martensitic nanodomains decorating the twins. These extended twin boundaries significantly enhance cyclic superelasticity, with 76% higher recoverable strain, 27% lower modulus, and reduced functional fatigue compared to solution-treated samples after 100 cycles. This work highlights a new strategy for optimizing SMA performance by introducing martensitic-nanodomains-nested B2 twins through cold rolling, offering fresh insights into microstructural design for improved functional stability. |