An investigation of constitutive modeling and 3D processing maps of Mg/HA composites for orthopedic applications

Abstract

The hydroxyapatite particles as reinforcement materials have been widely considered to produce magnesium biocomposites used in biodegradable implants. However, Mg/HA biocomposites, which show poor ductility at room temperature due to their intrinsic properties, must be deformed at elevated temperatures. Thus, optimum hot deformation conditions of Mg/HA biocomposites can improve the corrosion behavior of these materials in addition to their mechanical and microstructural properties. In the present study, the high-temperature deformation behavior of Mg/1wt.% HA and Mg/2.5 wt.% HA biocomposites have been scrutinized using compression tests in the temperature ranges of 523–673 K and strain rates between 0.005 and 0.1 s−1. The true stress-true strain diagrams, constitutive analysis, 3D processing map for power dissipation efficiency and instability in the strains from 0.1 to 0.6, and microstructural observations were assessed for both biocomposites. The results indicated that the proposed constitutive model could predict the Mg/HA biocomposites’ high-temperature deformation behavior with adequate accuracy. The activation energy which obtained from constitutive equations for both Mg/1wt.% HA and Mg/2.5wt.% HA biocomposites were identified to be 256.302 Kj/mol and 224.798 Kj/mol, respectively. According to 3D processing maps, the highest value of power dissipation efficiency for Mg/1wt.% HA has occurred in the strain of 0.2, strain rate of 0.005 s−1, and temperature of 573 K; however, for Mg/2.5wt.% HA, it has located at the strain, temperature, and strain rate of 0.3, 530 K, and 0.09 s−1, respectively. The microstructural characterizations showed more dynamic recrystallization occurrence in Mg/2.5wt.% HA than the Mg/1wt.% HA biocomposite.

Keywords

• Magnesium/hydroxyapatite biocomposite
• Hot deformation
• Constitutive analysis
• 3D processing map
• Microstructure evolution