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学历：博士研究生毕业
学位：工学博士学位
性别：男
学科：力学. 航空宇航科学与技术. 材料科学与工程. 机械工程. 冶金工程. 先进制造. 航空工程. 材料工程. 冶金工程. 机械工程. 固体力学
多尺度与微纳米力学，梯度结构材料，界面力学，固体本构关系，应变梯度理论，晶体塑性有限元，离散位错动力学，分子动力学，高熵合金，大数据与机器学习，材料基因，极端力学，高性能材料
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2023-03-12 论文“Enhanced strength-ductility synergy of medium-entropy alloys via multiple level gradient structures”在International Journal of Plasticity发表
Highlights
Multiple level gradient structured MEAs enhance strength-ductility synergy.
The crystal plasticity simulation, mechanical testing and microstructure characterization are employed to clarify the mechanical behavior and deformation mechanisms.
High order microbands and mechanical twins provide progressively strain hardening.
Design criterion for strength-ductility synergy via torsion-based treatments is proposed.
Abstract
The microstructures, mechanical properties, and deformation substructures of gradient Mo0.3NiCoCr medium-entropy alloys (MEAs) with very coarse grain size created by pre-torsion have been investigated. The strength of MEAs increases with the increase of torsion angle, while the tensile elongation nearly remains the same, suggesting the enhanced strength-ductility synergy. The initial dislocation density gradient structure after torsion and the following deformation substructure under tension are uncovered by means of electron backscatter diffraction (EBSD), electron channeling contrast imaging (ECCI), and transmission electron microscopy (TEM). The crystal plasticity finite element method (CPFEM) is employed to quantitively evaluate the evolution of dislocation densities and mechanical twinning volume fraction. The combination of experimental characterization and theoretical modeling enables to clarify the underlying strengthening and strain hardening mechanisms. The gradient distribution of dislocation created by the torsion leads to the rise of yield strength. Moreover, the high order of microbands, which arise from the activation of multiple slip systems during torsion, and additional mechanical twinning form in the gradient MEAs upon loading, constituting multiple level gradient structures. As the plastic strain goes on, the microbands can propagate and refine continuously, along with the interactions with the nano twins, in these MEAs with very coarse grain size up to ∼500 µm, which produce progressively high strain hardening and stabilize the plastic deformation over the whole deformation regime. This study thus offers guidance for optimizing the mechanical performance of structural materials via tuning the design of gradient structure.
Link
https://doi.org/10.1016/j.ijplas.2023.103592