Welcome! - Your Path to know me better
I am a fourth-year phd student at the laboratory of Thermalmechanical Metallurgy (LMTM) in École Polytechnique Fédérale de Lausanne (EPFL), Switzerland.
My research interests include martensite crystallography and mechanical behaviors in various alloy systems, such as Ti and NiTi.
Education
- 10. 2021 - Present PhD student
École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
- 09. 2017 - 07. 2020 Master
Beijing Institute of Technology, Beijing, China
- 09. 2013 - 07. 2017 Bachelor
Beijing Institute of Technology, Beijing, China
Selected Key Publications
The Role of Interaction Work in Martensite Deformation
J.F. Xiao, C. Cayron, R.E. Logé
Scripta Materialia, 2025
Abstract:
This study elucidates the evolution of martensite deformation via Interaction Work (IW). The IW is the mechanical work done by external loading, assisting deformation by competing with the energy barrier. This interplay establishes the maximum IW (IWmax) criterion for variant selection of different deformation modes. Considering multiple deformation modes (A, B, …), thanks to this competition, the deformation mode with minum IW is easily activated due to a low energy barrier, indicating that martensitic microstructures evolve along a trajectory of increasing IWmax of various deformation modes. We validated this hypothesis by examining reorientation and deformation twinning in monoclinic martensite (B19’) in NiTi, orthorhombic (α’’) and hexagonal martensite (α’) in Ti-based alloys, by comparing the predictions with existing literature.
EBSD study of variant reorientation, texture, and twin formation in a martensitic NiTi alloy deformed in compression
J.F. Xiao, C. Cayron, M. Van der Meer, R.E. Logé
Acta Materialia, 2024
Abstract:
Martensitic crystallography plays a vital role in the texture evolution and mechanical properties in Nickel-Titanium (NiTi) shape memory alloys when subjected to deformation. However, their microstructural changes during deformation are not well known and understood. In this study, we systematically investigate the stress-induced change of the microstructure of NiTi shape memory alloy under compression using the electron backscattered diffraction (EBSD) technique, and more specifically the variant reorientation, the evolution of textures, and the formation of twins. The EBSD maps reveal that upon strain the martensite morphologies shift from needle to block and their orientations are strongly reinforced along the loading axis. To quantify these microstructural changes, we used the Interaction Work (IW) associated with the lattice distortion of single variant, which provides a good fit with the experimental observation. A strong dependence of reorientation on the pre-textures of the parent B2 grains was also put in evidence. Other plasticity sources were confirmed such as dislocations and deformation twins. The calculations indicate that, for some specific orientations of parent grains, the active deformation twins could be easier for {011}M twin than that of (201 ̅)M deformation twin, whereas other orientations only favor the (201 ̅)M deformation twin.
Revealing the microstructure evolution of the deformed superelastic NiTi wire by EBSD
J.F. Xiao, C. Cayron, and R.E. Logé
Acta Materialia, 2023
Abstract:
The generation of irreversible macroscopic strains in superelastic NiTi alloys is an important issue closely related to the crystallography of the transformation from B2 austenite to B19’ martensite under stress. Although widely investigated at micro and nano scales by transmission electron microscopy (TEM), the observation of this phase transformation at the mesoscale is still lacking. In the present study, a superelastic NiTi wire was maintained in bending condition and investigated by electron backscattered diffraction (EBSD) technique. A strong variant selection and a formation of martensite texture were observed and quantified using the interaction work (IW) based on the distortion matrix of a single variant. A new habit plane between martensite and parent B2, {114}B2 || (201 ̅)M, was experimentally measured. It was explained by the Phenomenological Theory of Martensite Crystallography (PTMC) using dislocation slip {110}<001>B2 as lattice invariant shear (LIS). Some new B2 domains were also found in {114}B2 twinning relation with primary B2 grain. Two scenarios are proposed to explain them: a) the direct formation of {114}B2 deformation twin in B2, and b) a more complex one in which a primary B2 grain is transformed into a martensite variant, a (201 ̅)M deformation twin is formed inside this variant; then the (201 ̅)M twinned martensite reversely transforms into a new {114}B2 twinned B2 domain. The scenario b) permits to explain some uncommon (130)M, (201)M, and (101 ̅)M twins observed by EBSD between the martensite variants of the two {114}B2 twin-related B2 phases.
An investigation on reorientation and textural evolution in a martensitic NiTi rolled sheet using EBSD
J.F. Xiao, C. Cayron, R.E. Logé
International Journal of Plasticity, 2022
Abstract:
Variant reorientation is a ubiquitous phenomenon in shape memory alloys and has a great influence on their texture and mechanical response. In the present study, a martensitic NiTi rolled sheet is investigated by the electron backscattering diffraction (EBSD) technique; the variant reorientation and texture evolution are followed during bending. The initial weak texture components of martensite evolve by reorientation toward a strong texture around [1 ̅04]M and a weak one around [1 ̅12]M. The initial laths are transformed into blocks made of one or two variants. The EBSD maps were analyzed with the Interaction Work (IW) criterion associated with (a) the individual variant and (b) habit plane variants (a combination of two distortion variants). Compared with the experimental results, the prediction given with individual variant fits better than with the habit plane variants. An empirical quantification of the threshold on interaction work (IW) permits to rationalize and predict the variant pairs formed by the reorientation and their numbers in the blocks. A critical influence of the pre-texture of the parent B2 grains on the final texture and on the number of variants per block was revealed. This study could give insights into the mechanical response of the NiTi alloys with various textures during tensile and fatigue tests.
Role of stress-induced martensite on damage behavior in a
metastable titanium alloy
J.F. Xiao, X.K. Shang, J.H. Hou, Y. Li, B.B. He
International Journal of Plasticity, 2021
Abstract:
In general, stress-induced martensite (SIM) is frequently employed to enhance the strain hardening behavior of Ti alloys through a so-called transformation-induced plasticity (TRIP) effect. However, the SIM does not necessarily lead to the improved mechanical performance of Ti alloys with the underlying mechanism unclear yet. The present work investigates the damage behavior of a typical model metastable Ti-1023 alloy with dominant SIM using uniaxial tensile test and nano-indentation measurement. The full beta microstructure with varied grain size (70 μm-350 μm) is obtained in the present Ti-1023 alloy through careful heat treatments. The integrated mechanical and microstructural characterizations indicate that the SIM displays a dual impact on the damage behavior of the present Ti-1023 alloy. In particular, the SIM could either facilitate the nucleation of cracks or inhibit the propagation of cracks depending on the martensitic lath spacing. The above dual-impact of SIM on the damage of Ti-1023 alloy can be rationalized based on the competing role of martensitic lath spacing on the dislocation pile-up and damage nucleation at lath boundaries. The dislocation-based plasticity could additionally assist the crack blunting. The effect of the beta stability on the damage behavior is found to be indirectly determined by the martensitic lath spacing. Since the martensitic lath spacing is mainly governed by the beta grain size, the present work suggests that the grain boundary engineering should be harnessed to fully explore the potential of SIM in developing strong and ductile/tough Ti alloys for broad industrial applications.
Contact Me
Ecole Polytechnique Fédérale de Lausanne (EPFL)
Rue de la Maladière 71b, Neuchâtel 2002, Switzerland
junfeng.xiao@epfl.ch
Location
Microcity
Neuchatel, Switzerland