X-ray tomography study of “squeezed pores” in additively manufactured titanium alloy subjected to hot isostatic pressing

Abstract

Metal additive manufacturing is a fast-growing manufacturing technology for producing components with complex geometries and in short lead times. The widely used Ti6Al4V alloy has particularly good strength to weight ratio while having properties suitable for aerospace and medical industries. The additive manufacturing processes all involve layer by layer processing, often leading to small porosities in the final produced parts. These can lead to reduced mechanical properties, especially fatigue performance is negatively influenced. Hot isostatic pressing (HIP) has in recent years become an important post-process to eliminate these pores, improve the microstructure and enhance the fatigue performance of such parts. In this work, the pore closure and shrinkage due to HIP of Ti6Al4V is studied using high resolution laboratory and synchrotron tomography. This reveals “squeezed pores” which are visible only using high resolution synchrotron tomography and not in a typical laboratory resolution system. This paper reports on the imaging of such pores, handling of this data and discusses future work involving intentionally created defects of different morphologies and efforts to study their shrinkage behavior due to HIP processing.