Al-Mg-Si alloys are light weight and have excellent corrosion resistance, and are attracting attention as a liner material for high-pressure hydrogen containers in hydrogen fuel cell vehicles. Because it has excellent plastic hardening properties, it is also applied to car body panel materials, but it is moderate in strength, so research to improve the strength by adding Si-rich or Cu is in progress. So far, the authors have conducted research on the intergranular fracture of alloys with excessive Si addition from the macroscopic mechanical point of view, such as specimen shape. To evaluate their impact tensile properties, the split-Hopkinson bar impact test was performed using thin plate specimens of coarse and fine grain alloys of Al-Mg-X (X = Cr,Si) alloy. The effect of the shape of the specimen on the characteristics was studied through finite element method (FEM) analysis. As a result, it was found that the intergranular fracture of the alloy with excessive Si depended on the specimen width (W)/grain size (d), which can be expressed by the specimen size and grain size. As W/d decreases, the intergranular fracture transforms into a transgranular fracture. As the strain rate increases, the fracture elongation decreases, and the fracture surface of the intergranular fracture becomes more brittle. It was confirmed that intergranular fracture occurred in the high strain rate region even in materials with small grain sizes.

1. Introduction
2. Experimental Procedure
    2.1. Specimens
    2.2. Impact tensile test
    2.3. Tensile test
    2.4. Analysis methods
3. Results
    3.1. Mechanical properties
    3.2. Observation of the fracture surface
    3.3. FEM analysis results
4. Discussion
    4.1. Impact tensile properties
    4.2. Effect of strain rate on intergranular fracture
    4.3. Effect of specimen dimensions on intergranularfracture
5. Conclusion
Acknowledgement
References
Author Information

• Chang-Suk Han(Department of ICT Automotive Engineering, Hoseo University, Dangjin 31702, Republic of Korea) Corresponding author
• Min-Gyu Chun(Department of ICT Automotive Engineering, Hoseo University, Dangjin 31702, Republic of Korea)
• Sung-Soon Park(Department of ICT Automotive Engineering, Hoseo University, Dangjin 31702, Republic of Korea)
• Seung-In Lim(Department of ICT Automotive Engineering, Hoseo University, Dangjin 31702, Republic of Korea)