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<p>Electromechanical and thermal properties of Mg-Zn-Al and Mg-Zn-Al-Ca alloys prepared by squeeze casting are investigated utilizing calorimetry, resistivity and microhardness measurements during isothermal and non-isothermal annealing. The measurements are supplemented by microstructural observations by scanning and transmission electron microscopy and positron lifetime spectroscopy. In the as-prepared state, both alloys contain quasicrystalline phase with icosahedral structure at grain boundaries, probably <i>φ</i> phase (Mg<sub>5</sub>Al<sub>2</sub>Zn<sub>2</sub>) as evidenced by characteristic positron lifetime and its chemical composition. Decreases of resistivity at around 150&#xa0;°C and 190&#xa0;°C as well as the exothermal effect with maxima at similar temperatures are most likely due to a formation of disk-shaped hexagonal <i>β</i><sub>2</sub>´ phase (MgZn<sub>2</sub>) and block-shaped monoclinic <i>β</i><sub>1</sub>´ phase (Mg<sub>4</sub>Zn<sub>7</sub>). The precipitates, however, have negligible effect on microhardness. The third electrothermal response with maxima at around 250&#xa0;°C can probably be ascribed to a precipitation of trigonal <i>β</i> phase (Mg<sub>21</sub>Zn<sub>25</sub>) precipitates. The apparent activation energies were determined as <i>Q</i><sub>1</sub> (<i>β</i><sub>2</sub>´ phase) ~ 124&#xa0;kJ·mol<sup>-1</sup> for both alloys and <i>Q</i><sub>2</sub> (<i>β</i><sub>1</sub>´ phase) ~ 136&#xa0;kJ·mol<sup>-1</sup> in case of the Ca-alloy and<i> Q</i><sub>2</sub> ~ 130&#xa0;kJ·mol<sup>-1</sup> in case of base-alloy.</p>

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Microstructure and Electromechanical Properties of Squeeze Cast Mg-Zn-Al and Mg-Zn-Al-Ca Alloys During Heat Treatment

  • 期刊论文

  • 发表日期：

    2026年4月15日

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  • M. Leibner,
  • V. Kodetová,
  • M. Vlach,
  • I. Stulíková,
  • B. Smola,
  • J. Čížek,
  • J. Málek,
  • H. Kudrnová,
  • T. Kekule,
  • P. Hruška,
  • V. Mára

摘要

Electromechanical and thermal properties of Mg-Zn-Al and Mg-Zn-Al-Ca alloys prepared by squeeze casting are investigated utilizing calorimetry, resistivity and microhardness measurements during isothermal and non-isothermal annealing. The measurements are supplemented by microstructural observations by scanning and transmission electron microscopy and positron lifetime spectroscopy. In the as-prepared state, both alloys contain quasicrystalline phase with icosahedral structure at grain boundaries, probably φ phase (Mg5Al2Zn2) as evidenced by characteristic positron lifetime and its chemical composition. Decreases of resistivity at around 150 °C and 190 °C as well as the exothermal effect with maxima at similar temperatures are most likely due to a formation of disk-shaped hexagonal β2´ phase (MgZn2) and block-shaped monoclinic β1´ phase (Mg4Zn7). The precipitates, however, have negligible effect on microhardness. The third electrothermal response with maxima at around 250 °C can probably be ascribed to a precipitation of trigonal β phase (Mg21Zn25) precipitates. The apparent activation energies were determined as Q1 (β2´ phase) ~ 124 kJ·mol-1 for both alloys and Q2 (β1´ phase) ~ 136 kJ·mol-1 in case of the Ca-alloy and Q2 ~ 130 kJ·mol-1 in case of base-alloy.