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<p>The effects of calcium (Ca) addition on the microstructural, mechanical performance, tribological behavior, and corrosion resistance of pure magnesium (Mg) alloys were investigated. Mg-xCa alloys (where <i>x</i> = 0, 0.5, 1.0, 1.5, and 2.5&#xa0;wt.%) were fabricated using an ultrasonic stir casting method. X-ray diffraction (XRD) and microstructural analysis revealed the formation of Mg<sub>2</sub>Ca intermetallic phases with increasing Ca content, leading to grain refinement and strengthening of the alloys. Tensile and compressive tests showed significant improvements in yield strength, ultimate strength, and microhardness with Ca addition, attributed to grain boundary strengthening and secondary-phase hardening mechanisms. The optimum mechanical properties were achieved for the Mg-1.5Ca alloy, beyond which excessive Mg<sub>2</sub>Ca formation led to embrittlement. Dry sliding wear tests indicated enhanced wear resistance with increasing Ca content attributed to the existence of hard intermetallic phases and the formation of a protective oxide film. Potentiodynamic polarization test (PDP) and electrochemical impedance spectroscopy (EIS) studies in a 3.5&#xa0;wt.% NaCl electrolyte revealed improved corrosion resistance for Mg-xCa alloys compared to pure Mg. The Mg-1.5Ca alloy exhibited the best corrosion performance, attributed to the development of a stable and compact Mg(OH)<sub>2</sub> passive layer. However, the Mg-2.5Ca alloy showed reduced corrosion resistance due to the presence of micro-galvanic coupling between the Mg matrix and excessive Mg<sub>2</sub>Ca phases. The findings highlight the critical role of Ca in tailoring the microstructural and functional properties of Mg alloys, with potential applications in structural and biomedical fields.</p>

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Calcium-Driven Microstructural Evolution and Its Synergistic Effects on the Mechanical Strength, Tribological Performance, and Degradation Behavior of Mg-xCa Alloys

  • 期刊论文

  • 发表日期：

    2025年12月16日

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  • Madhav Kumar Jha,
  • Aviral Misra,
  • Vishal S Sharma,
  • Noe Alba-Baena

摘要

The effects of calcium (Ca) addition on the microstructural, mechanical performance, tribological behavior, and corrosion resistance of pure magnesium (Mg) alloys were investigated. Mg-xCa alloys (where x = 0, 0.5, 1.0, 1.5, and 2.5 wt.%) were fabricated using an ultrasonic stir casting method. X-ray diffraction (XRD) and microstructural analysis revealed the formation of Mg2Ca intermetallic phases with increasing Ca content, leading to grain refinement and strengthening of the alloys. Tensile and compressive tests showed significant improvements in yield strength, ultimate strength, and microhardness with Ca addition, attributed to grain boundary strengthening and secondary-phase hardening mechanisms. The optimum mechanical properties were achieved for the Mg-1.5Ca alloy, beyond which excessive Mg2Ca formation led to embrittlement. Dry sliding wear tests indicated enhanced wear resistance with increasing Ca content attributed to the existence of hard intermetallic phases and the formation of a protective oxide film. Potentiodynamic polarization test (PDP) and electrochemical impedance spectroscopy (EIS) studies in a 3.5 wt.% NaCl electrolyte revealed improved corrosion resistance for Mg-xCa alloys compared to pure Mg. The Mg-1.5Ca alloy exhibited the best corrosion performance, attributed to the development of a stable and compact Mg(OH)2 passive layer. However, the Mg-2.5Ca alloy showed reduced corrosion resistance due to the presence of micro-galvanic coupling between the Mg matrix and excessive Mg2Ca phases. The findings highlight the critical role of Ca in tailoring the microstructural and functional properties of Mg alloys, with potential applications in structural and biomedical fields.