6th Euro BioMAT 2021 - European Symposium on Biomaterials and Related Areas
Lecture
05.05.2021
Increasing the performance of Ti-6Al-4V hip stems by an intensive preforming
MB

Dr.-Ing. Margarita Bambach

Oerlikon Metco AG

Bambach, M. (Speaker)¹; Seifert, D.²; Sizova, I.³
¹GMT - Gesellschaft für metallurgische Technologie; ²Gesellschaft für metallurgische Technologie- und Softwareentwicklung mbH; ³Brandenburg University of Technology Cottbus-Senftenberg
Vorschau
23 Min. Untertitel (CC)

Precision drop forging is commonly used for manufacturing stems of grade 5 Titanium hip implants. However, due to the complicated part geometry, uneven strain distribution associated with a microstructure gradient may occur throughout the cross-section. The latter may negatively influence the material properties and lead to preliminary failure. This paper studies the possibility for improving the material performance of Ti-6Al-4V not by modifying its chemical composition but by introducing a pre-forming step by means of HDQT (High Deformation Quenching and Tempering) prior to forging the hip stem. The HDQT technology is an innovative intensive forming method which produces ultra-fine-grained microstructures and has already been applied successfully to steels. Now, a modified HDQT technology is transferred to Ti-6Al-4V for realizing high deformation degrees in several incremental forming passes. A final globular dual phase microstructure is adjusted by the repetitive incremental deformation of the initial material. In addition, twisting of the grains during deformation is a characteristic feature of the forming process. The latter is believed to provide effective obstacles to the crack propagation within the component and thus increase its damage tolerance during service. A combination with the following forging operation leads to an even strain distribution throughout the hip stem and a homogeneous microstructure. Ti-6Al-4V samples were manufactured by the process combination HDQT+forging. Their mechanical properties were studied in static and dynamic mechanical testing. The fatigue behaviour was determined in standard Woehler tests and in load increase tests. The damage tolerance of the material was studied in crack propagation testing. The process combination of HDQT pre-forming and final forging is a promising possibility to increase the lifetime of hip implants allowing for lightweight design and increased material performance. 

Abstract

Abstract

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