Chemistry Control in Electron Beam Deposited Titanium Alloys

Abstract

Direct manufacturing of metallic materials has gained widespread interest in the past decade. Of the methods that are currently under evaluation, wire-fed electron beam deposition holds the most promise for producing large-scale titanium parts for aerospace applications [1]. This method provides the cleanest processing environment as the deposition is performed under vacuum. While this environment is beneficial in preventing contamination of the deposit, there is the potential for preferential vaporization of high vapor pressure elements during the deposition process. This can lead to detrimental chemistry variations, which can have negative impacts on physical and mechanical properties. Past experience has shown that deposition of the alloy Ti-6Al-4V using electron beam direct manufacturing can produce material with aluminum content below the specification minimum [2]. As aluminum has a high vapor pressure with respect to titanium and vanadium, it preferentially vaporizes from the molten pool. This aluminum loss scales with the size of the molten pool and thus the chemical content can vary throughout the build. Compensating for this loss is necessary in order to achieve nominal chemistry in the deposited material. This paper examines established processing conditions for direct manufacturing of titanium, quantitatively determines deposited alloy chemistry changes under various conditions, and suggests a feedstock composition that will result in deposited material with nominal Ti-6Al-4V chemistry.

Elevated temperature characterization of electron beam freeform fabricated Ti–6Al–4V and dispersion strengthened Ti–8Al–1Er

“…A similar deficit in erbium content is noted. This is consistent with the loss of aluminum content due to vaporization that occurs during the electron beam additive manufacturing process that has been documented in other aluminum-bearing titanium alloys [19]. Composition values of interstitial elements, O, N, C, and H, were made only for the Ti-8Al-1Er wire feedstock and the subsequent electron deposited part.…”

The Effect of EBM Process Parameters on Porosity and Microstructure of Ti-5Al-5Mo-5V-1Cr-1Fe Alloy

“…When the speed was further increased (7800 mm/s), Al content decreased to 3.9 wt%. The results published by Brice et al [36] showed that the aluminum content dropped significantly also in the samples made from Ti-6Al-4V alloy processed by EBM. This is due to the fact that aluminum has higher vapor pressure than titanium and vanadium and thus vaporizes preferentially.…”

Metal Alloys for Fusion‐Based Additive Manufacturing

“…Most engineering alloys contain a range of alloying elements that could vaporize at high temperatures during metal AM. For example, vaporization that occurs for Al in Ti6Al4V and Mg in Al‐based alloys . The chemical composition of the final product is a key criterion that should be the same as that of the powder.…”