The macroscopic tensile plasticity of bulk metallic glasses (BMGs) is highly desirable for various engineering applications. However, upon yielding, plastic deformation of BMGs is highly localized into narrow shear bands and then leads to the "work softening" behaviors and subsequently catastrophic fracture, which is the major obstacle for their structural applications. Here we report that macroscopic tensile plasticity in BMG can be obtained by designing surface pore distribution using laser surface texturing. The surface pore array by design creates a complex stress field compared to the uniaxial tensile stress field of conventional glassy specimens, and the stress field scalarization induces the unusual tensile plasticity. By systematically analyzing fracture behaviors and finite element simulation, we show that the stress field scalarization can resist the main shear band propagation and promote the formation of larger plastic zones near the pores, which undertake the homogeneous tensile plasticity. These results might give enlightenment for understanding the deformation mechanism and for further improvement of the mechanical performance of metallic glasses.
The work was supported by MOST 973 of China (No. 2015CB856800) and the NSF of China (Grant No. 51271195, 5141101072, 11372323 and 11372110). The useful discussions and experimental help of D.Q. Zhao and D.W. Ding, and valuable discussions with H.Y. Bai, P. Wen and M.X. Pan are appreciated.
[Gao, Meng; Wang, Wei-Hua] Chinese Acad Sci, Inst Phys, Beijing 100190, Peoples R China; [Dong, Jie; Huan, Yong] Chinese Acad Sci, Inst Mech, State Key Lab Nonlinear Mech, Beijing 100190, Peoples R China; [Wang, Yong Tian] North China Elect Power Univ, Sch Energy Power & Mech Engn, Beijing 102206, Peoples R China