**4. Conclusions**

In this paper, the thermogenic physical model of the FSW process is established, and the finite element model of FSW is established. The material flow and temperature field in the welding process are studied by a numerical simulation. The finite element model is updated by the results of the axial force and torque tests. Moreover, the overall trend of the material flow in a finite element analysis is verified by the experiments on the weld cross section. The correctness of the finite element model analysis is verified by the microstructure formation and flow trend. Based on the results of this study, the following conclusions were made:


**Author Contributions:** H.L. and T.W. developed the FEM of friction stir welding process and wrote the paper; H.L., T.W. and P.W. conceived and designed the experiments; T.W. and Y.L. analyzed the data and modified the paper. T.W., F.Z. and H.W. performed the experiments.

**Funding:** The authors would like to acknowledge the financial support from the National Natural Science Foundation of China (Grant No. 51505470), the Youth Innovation Promotion Association, CAS and 'JXS' innovation fund, SIA.

**Conflicts of Interest:** The authors declare no conflict of interest.
