PSI - Issue 13

Yanning Guo et al. / Procedia Structural Integrity 13 (2018) 806–812 Yanning Guo/ Structural Integrity Procedia 00 (2018) 000 – 000

812

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a

b

c

d

Fig.7 Fracture morphologies of stirred zone: (a) 2024 400rmp-150mm/min(1300s -1 ), (b) 2024 600rmp-150mm/min(1300s -1 ); (c) 1300s -1 (400rmp 150mm/min) and (d) 2600s -1 (400rmp-150mm/min)

4. Conclusion [1] The flow stresses of dynamic impact have little instability near the yield point, and the force equilibrium is obtained only after plastic deformation. The strain rate strengthening effect is obviously obtained, and 2024 aluminum has been considered to have low strain rate sensitivity. [2] Under the same welding speed, higher rotation speed generates higher welding temperature, which leads to more refined grains and shows a higher strength of extension and ductility. It is shown that quiaxed and fine grains help to enhance the strength. [3] In stirred zone, crack propagation developed through grain boundaries, which gave it typical intergranular fracture surface. With the increase of strain rate, the fracture surfaces of stirred zone display smoother appearances with smaller dimples.

Acknowledgements

The study is supported by the National Natural Science Foundation of China under Grant No. 11572250.

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