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首先借助文献中报道的Zr-Nb合金体系中bcc相的热力学参数计算了Zr-Nb相图中处于混溶间隙内部的锆铌合金发生调幅分解的温度以及成分区间,然后通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等实验方法对部分成分的Zr-Nb合金进行验证。在实验过程中,首先不同成分锆铌合金均需在β单相区保温进行固溶处理,得到单一的bcc相,然后在预测的调幅分解温度下进行时效处理。研究结果表明,Zr-0.35Nb,Zr-0.4Nb和Zr-0.45Nb合金在不同温度下保温时,均在保温初期发生了调幅分解,表明调幅分解发生在相变初期;调幅分解温度越高,转变发生越迅速;调幅分解首先发生在晶界处,并逐渐向晶内转变;得到的组织与预测的调幅分解组织吻合较好。
Firstly, the temperature and composition interval of zirconium-niobium alloy in the intergranular interstitial gap in Zr-Nb phase diagram were calculated by the thermodynamic parameters of bcc phase in the Zr-Nb alloy system reported in the literature, and then X-ray diffraction (XRD ), Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and other experimental methods to verify the composition of the Zr-Nb alloy. During the experiment, zirconium-niobium alloys with different compositions were all subjected to solution heat treatment in β single-phase zone to obtain a single bcc phase, which was then aged at the predicted amplitude-modulation decomposition temperature. The results show that the amplitude modulation decomposition of Zr-0.35Nb, Zr-0.4Nb and Zr-0.45Nb alloys occurs at the initial stage of heat preservation when they are incubated at different temperatures, indicating that amplitude modulation decomposition occurs at the initial stage of phase transformation. The faster the transformation takes place, the amplitude modulation decomposition first takes place at the grain boundaries and gradually changes to the intragranular. The obtained tissue is in good agreement with the predicted amplitude modulation decomposition.