Controlling the microstructure and properties of wire arc additive manufactured Ti–6Al–4V with trace boron additions

Grain refinement of wire arc additively manufactured titanium by the addition of silicon

“…However, despite the differences between the casting and ALM processes, it is found from experimental observation that the growth velocities are reasonably similar. In previous work Bermingham et al investigated the solidification conditions between the ALM process used here and previous casting work by comparing the secondary dendrite arm spacing (SDAS) of boron containing titanium alloys [21]. In both casting [26] and ALM [21] processes it was found that the SDAS was comparable at approximately 25µm, indicating similar cooling rates during solidification.…”

“…The first build was a control sample and contained no silicon. Silicon was added to the subsequent two builds through the use of specially prepared silicon paints, in a similar fashion reported elsewhere [21]. Two silicon paints were used for this experiment: one with 25 wt% silicon and another with 40 wt% silicon.…”

Criticality of porosity defects on the fatigue performance of wire + arc additive manufactured titanium alloy

“…4(a). The prior β grains are about 1~3 mm wide, which is much larger than the prior β grain width reported in the selective laser melting and electron beam melting processed Ti-6Al-4V [7,15,36]. at the prior β grain boundary ( Fig.…”

“…Another cause for the test data scatter has been identified as the AM microstructure characteristics that are controlled by the cooling rate and peak temperature during deposition [12]. The volume fraction of α phase reported for WAAM Ti-6Al-4V is greater than 90% [13,14], with a predominantly Widmanstätten microstructure and an average α lath width of 1.5±1 µm [13][14][15]. The prior β grains are columnar and aligned in the build direction, which can lead to mechanical property anisotropy in terms of the tensile [5,16] and fatigue strength [5].…”

Modeling of Ti-W Solidification Microstructures Under Additive Manufacturing Conditions

“…These conditions would be expected to heavily favor planar interface breakdown and the development of cells and dendrites, [65] and experimental work on rapid solidification of β-Ti alloys has shown the dominant microstructural feature to be long columnar dendritic grains and/ or cellular structures heavily textured with the 〈001〉 directions aligned with the heat flow direction. [69][70][71] While these large thermal gradients typically give rise to a strong dendritic or cellular microstructure, reduction in G and _ T near the top of the melt pool may give rise to mixed columnar and equiaxed structure. [42] As shown later, the current model is capable of simulating all of these morphologies (cellular, dendritic, and equiaxed) under appropriate conditions.…”