Manufacturing of Osteosynthesis Systems Made of Magnesium Alloy AZ91

Hering, Britta; Wippermann, Andi; Mörke, Tobias; Grove, Thilo; Denkena, Berend

doi:10.1002/9781119274803.ch61

Cited by 1 publication

(1 citation statement)

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“…The same authors have further reported that higher burnishing force and feed lead to higher corrosion resistance [12]. Hering et al [13] have reported a similar conclusion, and shown that reduced roughness by ball-burnishing, at a large overlap of 75% and force of 200 bar, retards the degradation rate of AZ91 alloys. Burnishing with cryogenic cooling induces grain refinement and basal texture, which are attributed to increased hardness and the corrosion resistance of AZ31B [14] and Mg-Al-Zn alloys [15].…”

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confidence: 60%

Finite Element Analysis of Surface Integrity in Deep Ball-Burnishing of a Biodegradable AZ31B Mg Alloy

Uddin

Hall

Hooper

et al. 2018

Metals

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Abstract:As an effective and affordable technique, deep ball-burnishing has been applied to induce the plastic deformation of material, thus resulting in an increased surface hardness, compressive residual stress, and finish quality. Recent research shows that the fast degradation of an Mg alloy implant is a prime limiting factor for its success in in vivo human trials. This paper presents a comprehensive investigation into deep ball-burnishing of a biodegradable AZ31B Mg alloy, in order to improve the alloy's surface integrity. A series of experiments using an in-house built burnishing tool with a 10-mm steel ball have been conducted, with a key focus of exploring the influence of the major process parameters-e.g., burnishing force (750-2650 N), feed rate (150-500 mm/min), and step-over (0.05-0.15 mm)-on hardness and finish quality. With the aim of performing a parametric sensitivity study, a three-dimensional (3D) finite element (FE) model is developed to predict the deformation mechanics, plastic flow, hardness, and residual stress. The FE model agrees with the experiment, hence validating the reliability of the model. Results show that while burnishing significantly improves surface integrity compared to the untreated surface, burnishing force and step-over are shown to be dominant. The net material movement dictates generated residual stress (tensile or compressive), often negatively affecting the surface integrity (e.g., surface cracks), which may be responsible for the onset of corrosion. An appropriate burnishing strategy must therefore be planned, in order to achieve the intended process outcome. The resulting surface properties, enhanced by the deep ball-burnishing, are expected to potentially increase the corrosion resistance of AZ31B Mg alloy implants.

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