Integration of Deformation Processing with Additive Manufacture of Ti-6Al-4V Components for Improved β Grain Structure and Texture

Abstract

With Ti alloys like Ti-6Al-

The Effectiveness of Grain Refinement by Machine Hammer Peening in High Deposition Rate Wire-Arc AM Ti-6Al-4V

“…[3] The benefits of this are much more isotropic and consistent mechanical properties. [2,29,30] Why interpass rolling is so effective in refining the grain structure, when applying relatively low applied plastic strains (< 20 pct), is still the subject of on-going research. However, Donoghue et al [31,32] suggested that deformation and rapid re-heating can cause twinning of the b grains when they re-grow, though this is understood to be normally less favorable in Ti64.…”

In‐Situ High Temperature EBSD Analysis of the Effect of a Deformation Step on the Alpha to Beta Transition in Additive Manufactured Ti‐6Al‐4V

“…Irrespective of the exact mechanism, the observation of the growth of new orientations on re-hearting, due to twinning of the phase caused by the application of a low applied strain in AM, could in principle contribute to explaining the origin of the refined equiaxed prior-grain structure and textural weakening seen when AM is combined with deformation techniques, as described in [7] and [8]. However, there are additional questions that have been raised by this study that will need further future investigation.…”

“…The high cost of this material, combined with the inherent difficulty of machining, makes the fabrication of Ti-6Al-4V aerospace components a natural match with the emerging technologies of Additive Manufacture (AM), that are capable of producing near-net-shape parts [2][3][4][5][6][7][8][9]. However, it is widely acknowledged that AM processes produce very different microstructures and textures to those that are traditionally developed through thermo-mechanical processing (TMP) [10], and this can lead to a different property balance in AM components that needs to be better understood.…”

“…For example, peening using an Ultrasonic Impact Treatment (UIT) in Laser Blown Powder AM has been shown to lead to refined, equiaxed, prior-grains with more randomized orientations ( Fig. 1) [7]. The addition of a rolling step to Wire Arc Additive Manufacture (WAAM) has also been found to greatly reduce the prior grain size and cause a large reduction in texture strength, leading to improved mechanical isotropy [8,9] and this will be discussed in a future publication.…”

“…Figure 1. reconstructed EBSD orientation maps showing: a) typical columnar microstructure achieved by laser blown powder AM technique, b) the grain refinement obtained with in-process ultrasonic impact treatment applied every 5 layers, and c) treatment every layer [7].…”