Matrix/Precipitated Phase Interface Interaction of Deformation Age-Treated N36 Zirconium Alloy

Abstract:

N36 zirconium alloy specimens were prepared by the severe plastic deformation process of equal channel dual angle pressing (ECDAP), followed by annealing and aging treatment. The initial microstructure was observed by OM. The types and morphological characteristics of the precipitated phases were analyzed by SEM and TEM. The bonding mechanism at the interface between the α-Zr matrix and the (Zr,Nb)₂Fe precipitated phase after aging treatment was analyzed by combining the difference of valence electron density and the tensile strength. The influence of the precipitation behavior of the (Zr,Nb)₂Fe on the microstructure and properties of N36 zirconium alloy prepared by the ECDAP process was investigated. The results indicate that the ECDAP process can significantly refine the grain and promote the uniform distribution of the precipitated phase in N36 zirconium alloy, which mainly consists of Zr(Nb,Fe)₂ and (Zr,Nb)₂Fe with a large number of internal striated dislocations. The difference of valence electron density at the interface between the α-Zr matrix and the (Zr,Nb)₂Fe precipitated phase is 91.02%, and the lattice mismatch leads to increased resistance and instability of interfacial dislocation motion, which can generate susceptibility to relative motion and laminar dislocation initiation. Interfacial dislocations can induce matrix dislocation shifts to meet deformation demands. The increment in tensile strength after aging for 4 and 8 h reaches 2.14% and 10.36%, respectively, which is due to the increase in the reinforcement of the precipitated phase resulting from the strong electronic discontinuity between the precipitated phase and the matrix.