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<p>This study investigates the influence of post-process heat treatment (PPHT) on the microstructural characteristics, hardness, and corrosion behavior of friction stir processing (FSP) of AZ31 alloy. AZ31 plates have been friction stir processed with a cylindrical threaded pin tool at 1000&#xa0;rpm and 30&#xa0;mm/min, then annealing at 450&#xa0;°C for 5&#xa0;h. Microstructural analysis conducted after friction stir processing (FSP) using optical microscopy, SEM, and XRD revealed notable grain refinement and redistribution of precipitates. Subsequent post-process heat treatment (PPHT) led to moderate grain coarsening and enhanced phase stability. The mean grain size, initially 55&#xa0;µm in the base alloy, was refined to 4.5&#xa0;µm post-FSP and increased to 6.7&#xa0;µm after PWHT. SEM confirmed the existence of fine, uniformly dispersed precipitates in the FSP condition and controlled reprecipitation after heat treatment. XRD patterns demonstrated improved crystallinity, sharper α-Mg diffraction peaks, and refinement in the Mg17Al12 phase, along with reduced residual stresses. The hardness values rose progressively from 65.8 HV in the base metal to 75.2 HV after FSP, reaching 80.1 HV following PPHT. Tafel polarization results showed an increase in Ecorr from 0.13&#xa0;V in the base alloy to 1.10&#xa0;V after PPHT, and electrochemical measurements revealed better corrosion resistance with OCP values shifting from − 1.80&#xa0;V (base) to − 0.75&#xa0;V (FSP) and further to − 0.64&#xa0;V (FSP+PWHT). The FSP+PWHT combination yielded the most uniform microstructure, highest hardness, and greatest corrosion resistance among all conditions.</p>

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Enhancing Hardness and Corrosion Resistance in AZ31 Magnesium Alloy Through Friction Stir Processing and Post-process Heat Treatment

  • 期刊论文

  • 发表日期：

    2025年7月17日

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  • Namburi Harsha,
  • V. S. N. Venkata Ramana,
  • Koona Bhavani,
  • K. Sri Ram Vikas,
  • Rahul

摘要

This study investigates the influence of post-process heat treatment (PPHT) on the microstructural characteristics, hardness, and corrosion behavior of friction stir processing (FSP) of AZ31 alloy. AZ31 plates have been friction stir processed with a cylindrical threaded pin tool at 1000 rpm and 30 mm/min, then annealing at 450 °C for 5 h. Microstructural analysis conducted after friction stir processing (FSP) using optical microscopy, SEM, and XRD revealed notable grain refinement and redistribution of precipitates. Subsequent post-process heat treatment (PPHT) led to moderate grain coarsening and enhanced phase stability. The mean grain size, initially 55 µm in the base alloy, was refined to 4.5 µm post-FSP and increased to 6.7 µm after PWHT. SEM confirmed the existence of fine, uniformly dispersed precipitates in the FSP condition and controlled reprecipitation after heat treatment. XRD patterns demonstrated improved crystallinity, sharper α-Mg diffraction peaks, and refinement in the Mg17Al12 phase, along with reduced residual stresses. The hardness values rose progressively from 65.8 HV in the base metal to 75.2 HV after FSP, reaching 80.1 HV following PPHT. Tafel polarization results showed an increase in Ecorr from 0.13 V in the base alloy to 1.10 V after PPHT, and electrochemical measurements revealed better corrosion resistance with OCP values shifting from − 1.80 V (base) to − 0.75 V (FSP) and further to − 0.64 V (FSP+PWHT). The FSP+PWHT combination yielded the most uniform microstructure, highest hardness, and greatest corrosion resistance among all conditions.