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In this study, AZ31 Mg alloy was processed by a new severe plasticity deformation methodology with multi-pass lowered temperature, and the deformation behavior and microstructure evolution were investigated by finite element method and electron back-scattered diffraction technique and hardness. The results show that with the increase of deformation pass, the strain gradually springs, and its interval distribution tends to homogenize. Meanwhile, the effective strain increases dramatically with the shear force sudden upgrade in the deformation process. Moreover, the new deformation technique can refine grain size remarkably. With the passes on, {10-12} tensile twins behavior and the pyramidal < c + a > slip are triggered more frequently, leading to the completeness of dynamic recrystallization (DRX) gradually, which weaken and disperse the basal texture obviously. Besides, the standard deviation of hardness is getting smaller, and the maximum can reach 78.40 HV on average, which can be attributed to the even large strain distribution, complete DRX, and the high geometrically necessary dislocation.

The failure of the initial support of the tunnel caused by the synergistic deformation of steel and shotcrete under high‐ground stress is expected to be solved by arranging studs and steel webs to enhance the structure's bearing capacity. Hence, the bond‐slip mechanism of steel shotcrete with or without studs is unclear. This study aims to determine the bond behavior of the interface between the steel and shotcrete composite structure for tunnel support. The findings of push‐out experiments demonstrate that shotcrete on steel flange longitudinal splitting failure is the failure mode of natural bonding specimens. Tensile failure and expansion failure under the effect of studs is the failure mechanisms of stud steel‐sprayed concrete specimens. Furthermore, experimental data and a mathematical model establish the bond‐slip constitutive law of natural bonding and stud specimens. Finally, in addition to providing a theoretical foundation for the research of bond‐slip, the constitutive model put forward in this paper also supports the prevention of initial support failure in tunnel engineering.

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