## 4 Conclusions  
In this paper, the influence of different applied vibrations on the tensile properties (tensile strength and plasticity) of ME parts is studied experimentally. Specific conclusions are as follows:  
1. Applying vibration during the ME process can obviously improve the tensile strength and plasticity of Z-direction specimens and further enhance them with an increase in the vibration frequency or the amplitude. However, the effect on the specimens built in the X direction is small to negligible.
2. Applied vibration can greatly reduce the anisotropy of the ME parts, which can be further reduced with an increase in the vibration frequency or the amplitude.
3. The SEM analysis confirms that the specimens processed with applied vibration have fewer defects and better forming quality than the ordinary ones. With increasing  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Specimens (_i = 1–9_)** & \(Z_{0}^{0}\)_i_ & \(Z_{700}^{0.1}\)_i_ & \(Z_{700}^{0.2}\)_i_ & \(Z_{700}^{0.3}\)_i_ \\ \cline{2-5}  & \(X_{0}^{0}\)_i_ & \(X_{700}^{0.1}\)_i_ & \(X_{700}^{0.2}\)_i_ & \(X_{700}^{0.3}\)_i_ \\ \hline Average tensile strength difference (\%) & 127.4 & 60.0 & 50.9 & 42.0 \\ Average plasticity difference (\%) & 77.9 & 47.1 & 46.9 & 42.8 \\ \hline \hline \end{tabular}
\end{table}
Table 7: The tensile property anisotropy of the specimens processed without applied vibration and with vibrations of different amplitudes.  
Figure 11: Tensile property anisotropy of the specimens processed without applied vibration and with different applied vibrations. (**a**) The effect of different vibrations (700 Hz frequency with different amplitudes) on the specimens’ tensile strength anisotropy and (**b**) the effect of different vibrations (700 Hz frequency with different amplitudes) on the specimens’ plasticity anisotropy.  
vibration frequency or amplitude, the specimens' defects are further reduced and the forming quality is further improved.
4. The proposed novel method, introducing vibration into the ME process by using piezoelectric ceramics, could make such specimens denser in structure and with stronger adhesive strength, thereby improve the forming quality. This method is also applicable for other additive manufacturing techniques to improve the forming quality of built parts.  
Conceptualization, S.J.; data curation, T.D. and Y.Z.; formal analysis, S.J., T.D. and Y.Z.; funding acquisition, S.J.; investigation, T.D., Y.Z. and W.D.; methodology, S.J. and M.Z.; project administration, S.J.; resources, S.J., T.D. and M.Z.; software, T.D.; supervision, S.J.; validation, S.J., T.D. and Y.Z.; writing--original draft preparation, T.D. and Y.Z.; writing--review and editing, S.J. and W.D. All authors have read and agreed to the published version of the manuscript.  
The work described was supported by the National Natural Science Foundation of China (51705068) and the fundamental research funds for central universities (N180703009 and N170302001).  
I confirm that the manuscript has been submitted solely to the journal and that it is not published, in press, or submitted elsewhere. I confirm that all the research meets the ethical guidelines, including adherence to the legal requirements of the study country. I confirm that I have seen, read, and understood the guidelines on copyright. I confirm that the names of all the co-authors have been included in the manuscript and that these co-authors all had an active part in the final manuscript.  
All available. Contact the corresponding author for data.  
No potential conflict of interest is reported by the authors.