Quench Sensitivity of AA7N01 Alloy Used for High-Speed Train Body Structure
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The quench sensitivity of AA7N01 aluminum alloy used for high-speed train body structure was investigated by end-quenching test, time–temperature-transformation curves simulation, transmission electron microscopy and scanning transmission electron microscopy. The hardness decreased with the increasing distance from the quenched end, and the depth of the age hardening layer was about 50 mm. The simulation results showed that the high quench sensitivity temperature was between 230°C and 300°C and the critical cooling rate should be larger than 2°C/s. The decrease of hardness along the increasing distance from the quenched end was attributed to the coarsening of the η equilibrium phase and the widening of the precipitate-free zone. The high-angle annular dark field results provided the direct evidence of the induced-precipitation effect of Al3Zr particles during the quenching process.
The authors acknowledge the financial support by National Key Research and Development Program of China (2017YFB0305500), National Natural Science Foundation of China (Grant No. U1637210) and Introduction Program for Postdoctoral International Exchange.
Conflict of interest
The authors declare that they have no conflicts of interest.