Microstructure and mechanical properties of 7A56 aluminum alloy after solution treatment

Abstract

The effect of solution treatment on the microstructure and mechanical properties of a novel 7A56 aluminum alloy plate was investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), conductivity, hardness and tensile tests. The results indicate that the coarse second phases in the hot-rolled plate mainly consist of AlZnMgCu quaternary phase and Al7Cu2Fe phase, and no Al2CuMg phase is found. The amount of the second phases gradually reduces with the increase in temperature (450–480 °C) and time (1–8 h) during the solution treatment, and the soluble particles are completely dissolved into the matrix after solution treatment at 470 °C for 4 h, while the residual phases are mainly Fe-rich phase along the grain boundaries. The recrystallization fraction of the alloy gradually increases with the degree of solution treatment deepened. When the temperature exceeds 480 °C, over-burning takes place. The mechanical properties of samples treated at 470 °C for various times were tested. After the solution treated at 470 °C for 4 h, the quenching conductivity and peak-aged hardness of the alloy are 30.8%IACS and HV 204, respectively. The ultimate tensile strength and yield strength of the samples aged at 120 °C for 24 h are 661 and 588 MPa, respectively.

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Acknowledgements

This work was financially supported by the National Key Research and Development Program of China (No. 2016YFB0300803), the National Natural Science Foundation of China (No. 51274046) and the National Key Basic Research Program (No. 2012CB619504).

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Correspondence to Bao-Hong Zhu.

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Guo, FB., Zhu, BH., Jin, LB. et al. Microstructure and mechanical properties of 7A56 aluminum alloy after solution treatment. Rare Met. 40, 168–175 (2021). https://doi.org/10.1007/s12598-017-0985-7

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Keywords

  • 7A56 aluminum alloy
  • Solution treatment
  • Aging treatment
  • Microstructure
  • Properties