Fabrication of a gradient AZ91-bioactive glass composite with good biodegradability

Abstract

This study used friction stir-back extrusion to fabricate the AZ91 + 3 wt% bioactive glass gradient composite wire. The microstructure, mechanical properties, and corrosion resistance of a material in a simulated body fluid were investigated. Three 2-mm diameter holes with varying hole patterns were drilled in the cross-section of the AZ91 rod to apply 3 wt % bioactive glass to the AZ91 matrix. The results demonstrated that the hole pattern strongly influenced the material's flow in the extruded wire's cross-section. By increasing the distance between the center of the initial rod and the center of the holes, a higher temperature and more uniform distribution of plastic strain are formed during friction stir back extrusion, resulting in uniform distribution of bioactive glass particles and α + β eutectic structure near the surface of composite wires. Introducing bioactive glass particles into the zone near the surface of the AZ91 rod results in the formation of a uniform distribution of bioactive glass particles near the surface and their absence in the central zone of the composite wire. A higher amount of discontinuous β-Mg₁₇Al₁₂ phase and α + β eutectic formed at the grain boundaries by increasing the temperature and plastic strain during friction stir-back extrusion. The crystallographic texture of the AZ91 rod changed from prismatic to basal and pyramidal due to the friction stir-back extrusion method. A gradient AZ91-bioactive glass composite wire with ultimate tensile strength, yield strength, elongation, and corrosion resistance 58, 64, 62, and 34%, respectively, greater than AZ91 as-cat rod can be produced by inserting bioactive glass powder using a hole drilling method and applying a friction stir back extrusion process.

Keywords: AZ91 matrix composite; Bioactive glass; Friction stir back Extrusion.; Gradient structure.