Extrusion of Magnesium Tubes for Biodegradable Stent Precursors

Abstract

Production of stent precursors in the form of small-size tubes has been evaluated by hot compression tests and extrusion trials on the AZ31B and ZM21 magnesium alloys. The investigation here presented mainly reports on the effects of extrusion parameters on microstructure and properties of the tubes. Processing at 410°C and at slow strain rate (2.78 · 10⁻³ s⁻¹) by a laboratory hot-extrusion system allowed producing small-size tubes featuring a homogeneous and refined equiaxed grain structure. Microstructural analyses showed that dynamic recrystallization, often anticipated by deformation twinning, took place during hot forming. By a proper control of extrusion parameters, tubes with wall thickness as low as 0.5 mm could be successfully produced.