The Influence of Aging Temperature on the Microstructure, Mechanical Properties, and Biodegradation Behavior of an AZ91 Magnesium Alloy for Biomedical Implants

¹ Production Engineering & Metallurgy College, University of Technology-Iraq, Baghdad 10066, Iraq.
² Department of Power Mechanics Technologies, Al-Farqadein University College, Basrah 61004, Iraq

Published online: 24 June 2026

Abstract

The effect of aging temperature on the microstructure, mechanical properties, and biodégradation behavior of an AZ91 magnesium alloy intended specifically for biomedical implants was thoroughly investigated in this in-depth study. A detailed series of aging treatments were meticulously conducted at various temperatures including 125 °C, 150 °C, 175 °C, 200 °C, 225 °C and 250 °C for a duration of precisely 24 hours for each individual condition. The extensive microstructural analyses revealed significant grain size growth along with a marked and noticeable increase in the volume fraction of the ß-Mg17Al12 phase as the aging temperature was raised progressively. A comprehensive analysis of the mechanical properties indicated that the specimen which was aged at 175 °C exhibited the highest levels of hardness and yield strength, which can be attributed directly to the precipitation of the β phase during the aging process. Furthermore, the biodegradation evaluations demonstrated that the in-vitro corrosion rate experienced a noteworthy decrease up to the critical aging temperature of 175 °C, after which it increased significantly as further elevation of the aging temperature occurred. These findings clearly underscore the critical influence of aging temperature on the performance characteristics of the AZ91 alloy, particularly in relation to its overall suitability and efficacy for various biomedical applications, emphasizing the need for careful consideration of aging conditions in the development of AZ91 magnesium alloy.