INVESTIGATION OF CREEP AND FATIGUE BEHAVIOR OF ADDITIVELY MANUFACTURED Ti6Al4V ALLOY

Abstract

Additive Manufacturing (AM) technology has seen significant advancements in recent years, enabling its integration across diverse industries such as aerospace, automotive, biomedical, and chemical sectors. The Titanium Ti6Al4V alloy is among the most preferred alloys for these applications, primarily due to its excellent mechanical properties and the relative ease with which it can be processed through additive manufacturing techniques. The Ti6Al4V alloy is used in the fabrication of compressor modules, hip joint implants, aircraft fuel nozzles, turbine blades, dental implants, aero-engine fans, etc., in their respective industries. The additive manufacturing process enables the creation of complex and customized geometries with close dimensional tolerances. Despite many advantages, the parts fabricated with the additive manufacturing technique are associated with several manufacturing challenges, such as high thermal stress gradient, inferior surface quality, inherent process-induced porosity, and defects. These inherent defects are supposed to be detrimental factors for the degraded monotonic and cyclic properties of the metallic parts. An insight is thus required into the role of the defects and inhomogeneity on the fatigue behavior of the alloys for better design and reliability of the additively manufactured parts. The combined influence of microstructural evolution and inherent defects of additively manufactured Ti6Al4V alloy on fatigue properties is rarely traced, and this study attempts to bridge the research gap. Post-processing treatment techniques can be employed to mitigate these adverse effects generated during the additive manufacturing process. Post-heat treatment is considered one of the effective methods for relieving the process-generated high tensile residual stress and controlling the microstructure of the material. Hot isostatic pressing (HIP) treatment is another effective postprocessing approach to reduce the porosity fraction in AM parts by the application of pressure at elevated temperatures. This post-processing technique has been found to be effective in reducing the size and fraction of defects, enhancing overall material properties, although it may not completely eliminate all imperfections. Extensive research has been performed on individual postprocessing treatments, such as heat treatment, HIP treatment, surface finishing, etc., highlighting their positive impact on the mechanical properties of additively manufactured alloys. However, limited literature is available on the effect of a sequential combination of post-processing on the fatigue performance of SLM Ti6Al4V alloy, which is an important aspect in the damage evaluation of additively manufactured alloys. More insight is thus required to fully understand the effect of a sequential combination of post-processing techniques and develop comprehensive post-processing frameworks that leverage the unique advantages of each treatment method for improved performance and reliability of additively manufactured alloys.