# Interdiffusion in Zr-Mo/W Intermetallics
## 4 Conclusions  
In this paper, the interdiffusion behavior of the Zr-Mo and Zr-W binary systems at 1300 \({}^{\circ}\)C, 1400 \({}^{\circ}\)C, and 1500 \({}^{\circ}\)C was systematically investigated by the solid-solid diffusion couple. The conclusions are as follows:  
1. For the Zr-Mo binary system, the (Zr, Mo) solid solution phase with concentration gradient and Mo\({}_{2}\)Zr phase were formed in the diffused region at 1300-1500 \({}^{\circ}\)C. At 1300 \({}^{\circ}\)C, 1400 \({}^{\circ}\)C, and 1500 \({}^{\circ}\)C, the thickness of the (Zr, Mo) solid solution was 297 \(\upmu\)m, 443 \(\upmu\)m, and 753 \(\upmu\)m, respectively. The thickness of the Mo\({}_{2}\)Zr was 4.48 \(\upmu\)m, 5.62 \(\upmu\)m, and 7.20 \(\upmu\)m, respectively. For the Zr-W binary system, the W\({}_{2}\)Zr phase was formed in the diffused region. At 1300 \({}^{\circ}\)C, 1400 \({}^{\circ}\)C, and 1500 \({}^{\circ}\)C, the thickness of the W\({}_{2}\)Zr was 4.15 \(\upmu\)m, 7.52 \(\upmu\)m, and 14.22 \(\upmu\)m, respectively.  
2. The growth constants of Mo\({}_{2}\)Zr and W\({}_{2}\)Zr with temperature in accordance with the Arrhenius relationship, and the calculated activation energy of Mo\({}_{2}\)Zr and W\({}_{2}\)Zr phase growth was 109 kJ/mol and 285 kJ/mol, respectively.  
3. In the diffusion process of the Zr-Mo system, the formation of (Zr, Mo) solid solution resulted in a decreased chemical potential for the formation of Mo\({}_{2}\)Zr. The interdiffusion coefficient of the (Zr, Mo) solid solution phase showed concentration dependence, which decreased with the increase of Mo content. Additionally, the activation energy of diffusion of the (Zr, Mo) solid solution phase was 145-170 kJ/mol at a Mo content of 2-10 at. %.  
Methodology, K.W., X.L. and T.L.; conceptualization, X.L. and J.L.; investigation and formal analysis, K.W., C.H. and X.L.; data curation and writing--original draft, K.W. and T.L.; validation, C.H.; writing--review and editing, X.L. and J.L. funding acquisition, X.L. and J.L. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Natural Science Foundation of China (Grant number 52001026), the Science and Technological Innovation Program of Beijing Institute of Technol  
Figure 9: Activation energy corresponding to different concentrations of elements in (Zr, Mo) solid solution phase.  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline  & **0.02 at.** & **0.04 at.** & **0.06 at.** & **0.08 at.** & **0.1 at.** \\ \hline D\({}_{0}\)/10\({}^{-8}\) m\({}^{2}\)s & 2.779 & 4.207 & 4.607 & 4.481 & 5.231 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Pre-exponential factors D\({}_{0}\) at different Mo element concentrations.  
ogy (Grant number 2022 CX01012), and the Beijing Institute of Technology Research Fund Program for Young Scholars (Grant number XSQD-202210006).  
Not applicable.  
**Data Availability Statement**: Data will be made available on request.  
China National Key Laboratory of Science and Technology on Materials under Shock and Impact is acknowledged.  
The authors declared that they have no conflict of interest in this work.