Hermith optimises titanium alloy wire production for Additive Manufacturing
April 17, 2025
Researchers at Hermith GmbH, based in Munich, Germany, have reported on their work to improve the manufacturing of titanium Ti-6Al-4V wire and optimise its quality for use as Additive Manufacturing feedstock.
Founded in 2004, Hermith has grown into one of Europe’s leading titanium suppliers. After thirteen years as a trader and stockholder, the company launched its own TÜV-certified production facility in 2017, allowing it to offer customised titanium solutions.
Titanium alloys play a crucial role in aerospace, medical, and automotive industries due to their exceptional strength and corrosion resistance. Ti-6Al-4V, in particular, is valued for its high strength, low weight, and durability in extreme conditions.
With the rapid growth of Additive Manufacturing, the demand for high-quality titanium wire has surged. However, the authors state that challenges remain in reducing material losses, lowering energy costs for heat treatment, and achieving a homogeneous fine-grained structure to enhance strength and ductility while preventing wire breaks.
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Problems of titanium wire manufacturing processes
The Additive Manufacturing market employs various methods to produce wire from (α+β) titanium alloys, including heating, deformation, and annealing. High-strength wire production typically involves billet creation, hot deformation into a rod, cold drawing, and final heat treatment. However, current methods have several drawbacks. These are said to include:
- Multiple deformation stages with heating, along with energy-intensive etching and vacuum annealing
- Oxidation and surface cracking, causing structural inhomogeneity and variability in mechanical properties
- Long processing times and lower mechanical performance compared to improved methods.
Ti-6Al-4V, a widely used titanium alloy in Additive Manufacturing, consists of titanium, 6 wt.% aluminium, 4 wt.% vanadium, and less than 0.20 wt.% oxygen. Known as VT6 in aerospace, it is used for large welded structures, pressure vessels (operating from -196°C to 450°C), and other critical components. For AM applications, wire must feature enhanced microstructural homogeneity, controlled phase composition, minimal anisotropy, and be free from defects such as welded joints.
Hermith’s solution for wire manufacturing
The improved process results in wire with reduced anisotropy of mechanical properties, produced as a single piece without welded joints, at a minimum length of 8,500 m – reported to be ideal attributes for Additive Manufacturing applications.
This is achieved through an advanced manufacturing method using induction heating and process control based on temperature and acoustic emission monitoring. The process involves multiple deformation stages, drawing or rolling the billet from 8.0 mm to 1.6 mm in diameter. Induction heating is applied with:
- 50-70 kW power at 40-80 kHz for billets from 8.0 mm to 4.0 mm.
- 20-40 kW power at 300-500 kHz for billets under 4.0 mm to 1.6 mm.
Deformation is carried out at 400-700°C with a tolerance of ±10°C and a deformation degree of 10-50% per pass, calculated as:
μ = (d²i – d²(i+1)) / d²i × 100, where di and d(i+1) are the wire diameters before and after each pass. The deformation degree is controlled via acoustic emission energy parameters, ensuring process stability and wire quality.
To ensure the highest quality titanium alloy wire for Additive Manufacturing, precise induction heating is used to maintain uniform temperature distribution along the wire’s length and cross-section. This minimises temperature variations, reducing scale formation and contamination from airborne impurities, which enhances the alloy’s overall quality during heat treatment.
Additionally, accurate and rapid temperature control is crucial for achieving superior wire characteristics, ensuring consistency and reliability in the final product.
Results
Induction heating of titanium alloy wire poses challenges in achieving uniform temperature distribution due to high-frequency current behaviour, titanium’s low thermal conductivity, and thermal losses.
The research identified optimal inductor power levels and current frequencies based on wire diameter. Experiments were conducted to refine heating modes, ensuring minimal anisotropy in mechanical properties and phase composition for high-quality Additive Manufacturing wire.
Optimal induction heating parameters were determined based on wire diameter. For billets of 8.0–4.0 mm, the best conditions were 50-70 kW power at 40-80 kHz, while for 4.0–1.6 mm billets, 20-40 kW at 300-500 kHz was ideal.
In the proposed method, billets were heated between 400-700°C using two inductors of varying power. Drawing was performed at 620 ± 10°C, resulting in wire with acceptable mechanical properties, including an acoustic emission threshold below 0.02 × 10⁻³ mV²/s and a plasticity parameter above 3.2 mm. While the wire met quality standards, the low deformation rate extended production time significantly, making the process economically unfeasible.
The results produced a fine-grained structure with uniform grain distribution, and the wire-maintained straightness. However, this deformation regime offered no clear advantages over methods without controlled heating intervals. While the wire met quality standards, the process’s economic feasibility remains a concern. (see Table 1)
| Step of deformation | Tensile strength, MPa | Yield strength, MPa | Plasticity, mm | Tensile strength, MPa |
| 1 | 978/970 | 923/931 | 3,1/3,0 | No |
| 2 | 978/970 | 923/931 | 2,9/2,9 | No |
| 3 | 978/970 | 923/931 | 3,0/3,0 | No |
| 4 | 978/970 | 923/931 | 3,2/3,1 | No |
| 5 | 978/970 | 923/931 | 3,1/3,0 | No |
The proposed method for producing (α+β) titanium alloy wire for Additive Manufacturing, using induction heating and process control via acoustic emission and temperature monitoring, enhances strength and plasticity. The wire achieves a homogeneous, fine-grained structure and is produced in lengths of at least 8500 mm without welded joints.
Key findings:
- Heating the billet to Tz = (400–700)°C during drawing or rolling is crucial for ensuring uninterrupted processing and high-quality wire.
- Maintaining a temperature tolerance of ±10°C improves wire
- Controlling deformation based on acoustic emission reduces rolling passes while maintaining strength and plasticity.
This method enables the production of Ti-6Al-4V wire for Additive Manufacturing without welding, ensuring consistent mechanical properties throughout its length.
