Effect of Ca and Rare Earth Elements on Impression Creep Properties of AZ91 Magnesium Alloy |
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Authors: | B Nami H Razavi S Mirdamadi SG Shabestari SM Miresmaeili |
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Affiliation: | (1) Center of Excellence for Advanced Materials and Processing (CEAMP), Narmak, Tehran, Iran;(2) School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran, Iran;(3) Department of Mechanical Engineering, Shahid Rajaee Teacher Training University (SRTTU), Lavizan, Tehran, Iran;; |
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Abstract: | Creep properties of AZ91 magnesium alloy and AZRC91 (AZ91 + 1 wt pct RE + 1.2 wt pct Ca) alloy were investigated using the
impression creep method. It was shown that the creep properties of AZ91 alloy are significantly improved by adding Ca and
rare earth (RE) elements. The improvement in creep resistance is mainly attributed to the reduction in the amount and continuity
of eutectic β(Mg17Al12) phase as well as the formation of new Al11RE3 and Al2Ca intermetallic compounds at interdendritic regions. It was found that the stress exponent of minimum creep rate, n, varies between 5.69 and 6 for AZ91 alloy and varies between 5.81 and 6.46 for AZRC91 alloy. Activation energies of 120.9 ± 8.9 kJ/mol
and 100.6 ± 7.1 kJ/mol were obtained for AZ91 and AZRC91 alloys, respectively. It was shown that the lattice and pipe-diffusion-controlled
dislocation climb are the dominant creep mechanisms for AZ91 and AZRC91 alloys, respectively. The constitutive equations,
correlating the minimum creep rate with temperature and stress, were also developed for both alloys. |
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