变形时效处理N36锆合金基体/沉淀相界面相互作用研究

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

摘要:

采用等通道双转角挤压（equal channel dual angle pressing, ECDAP）大塑性变形工艺制备N36锆合金试样，并进行退火和时效处理。使用OM观察了初始显微组织，使用SEM及TEM分析了沉淀相种类及形貌特征。结合价电子密度差与抗拉强度，分析了时效处理后α-Zr基体与(Zr,Nb)₂Fe沉淀相界面的键合机制，探究了(Zr,Nb)₂Fe颗粒析出行为对ECDAP工艺制备N36锆合金组织及性能的影响。结果表明：ECDAP工艺可以显著细化晶粒，并促进N36锆合金中沉淀相的均匀分布。析出相主要由Zr(Nb,Fe)₂和(Zr,Nb)₂Fe组成，并有大量的内部条纹位错。α-Zr基体与(Zr,Nb)₂Fe沉淀相界面处的价电子密度差为91.02%，晶格失配导致界面位错运动阻力增大，不稳定性提高，易产生相对运动并引发层错。界面位错可能诱导基体位错移动以满足变形需要。4和8 h时效后N36锆合金抗拉强度增幅分别达到2.14%和10.36%，这是由于沉淀相与基体间的强电子不连续性导致的第二相强化增加。

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.