Influence of Warm Bending on the Surface Topography of Titanium Alloy Ti-6Al-4V

Abstract

More frequently industry reverts to titanium alloys such as Ti-6Al-4V for several applications. This is due to its wide range of positive material characteristics like high biocompatibility, good corrosion resistance and high specific strength. Hence, Ti-6Al-4V is utilized for applications in medicine technique, marine and aerospace. However, forming of Ti-6Al-4V at room temperature is limited, which is caused by its hexagonal closed packed (hcp) grain structure. To overcome these limitations it is necessary to form Ti-6Al-4V at elevated temperatures. Thus, further gliding planes are activated and large scaled parts can be formed at low cycle times. Another promising process to generate Ti-6Al-4V structures is additive manufacturing. Via Laser Beam Melting (LBM) geometrical limitations of the forming process can be overcome. Nearly every conceivable geometry like undercuts is possible to generate. However, the process takes comparatively long time and the costs for large batch sizes are high. In order to merge the advantages of forming and LBM a combination of both processes is favorable. The sequence of forming and a subsequent additive process to produce a hybrid part leads to several challenges. Besides forming induced residual stresses in the sheet metal, the topography of the sheet has effect on the bonding quality of sheet metal and additive structure. Especially peaks in roughness may serve as crack initiators. In order to provide suitable parts for the subsequent additive process it is necessary to have a sound knowledge of the impact of the forming operation on the surface topography. For this reason this paper focuses on the investigation of the influence of warm bending on the surface topography of Ti-6Al-4V. Therefore bending tests with varying temperatures, punch radii and different bending angles are conducted and the topography is analyzed with confocal microscopy.