What TC4 Titanium Alloy Is and Where It Is Used
TC4 is the Chinese designation for the alpha+beta titanium alloy Ti-6Al-4V, which corresponds to Grade 5 in the ASTM grade system. It contains about 6 percent aluminium and 4 percent vanadium as the main alloying additions, and it is the most widely consumed titanium alloy in the world. Plate and strip are supplied to ASTM B265 and AMS 4911, bar and rod to ASTM B348, and the wrought implant grade is covered by ASTM F1472 and ISO 5832-3, which is the correct reference for the wrought Ti-6Al-4V material often loosely quoted as ISO 5832-2.
The alloy is selected for aerospace, chemical and biomedical applications because of its corrosion resistance, high specific strength, good toughness and excellent biocompatibility. Its limitation is on the manufacturing side rather than the material side: with conventional subtractive processes, material utilisation is low, manufacturing cost is high and deformation is difficult, which restricts wider use. Additive manufacturing, also called 3D printing, is the technology that changes this balance.
How Additive Manufacturing Works
Additive manufacturing originated in the rapid prototyping technology of the 1990s. Unlike subtractive manufacturing, it works on a discrete and stacking principle: a computer model of the three-dimensional solid part is cut into a series of thin slices of a defined thickness, the machine processes the data for each slice and builds the slices one after another until a dense solid part is produced.
The method suits parts of almost any geometry and offers high material utilisation, low cost, high flexibility and a high degree of integration, which is exactly what a hard-to-machine alloy such as TC4 needs. Where a forged blank would have to be machined down with most of the material turned into chips, additive manufacturing deposits material only where the design requires it.
Comparing SLM, LENS and EBM
The three additive processes most often used for titanium alloys differ in energy source, build environment and typical duty.
| Process | Energy source | Build environment | Typical role |
|---|---|---|---|
| Selective laser melting (SLM) | Laser beam | Inert gas atmosphere | Fine features, high dimensional accuracy, small to medium parts |
| Laser engineered net shaping (LENS) | Laser beam with powder feed | Inert gas shielding | Near-net shape deposition and repair of existing parts |
| Electron beam melting (EBM) | Electron beam | Vacuum chamber | Higher build rates, larger parts, low residual stress |
Why EBM Fits TC4 Titanium Alloy
Electron beam melting has a set of advantages that make it particularly suitable for TC4:
The electron beam is used as the energy source and is not reflected during the manufacturing process, so energy utilisation is high.
Melting takes place in a vacuum, which effectively avoids contamination by other elements from the air.
The high energy input and high scanning speed give a higher build efficiency than the other two processes.
Parts built by EBM carry lower residual stress and do not require subsequent heat treatment, which saves energy and shortens the production route.
Microstructure and Post-Treatment of EBM TC4
Published research on EBM forming of TC4 shows a characteristic solidification structure: the macrostructure consists of columnar crystals growing along the building direction, and the microstructure is an alpha plus beta lamellar structure. The faster the cooling rate, the easier it is to obtain a finer microstructure, which is why scan strategy and layer thickness matter as much as alloy composition.
Optimisation of the process parameters gives EBM the best energy density and effectively avoids the generation of a large number of defects. A subsequent hot isostatic pressing treatment removes porosity and homogenises the microstructure, which improves fatigue properties significantly, although it also leads to grain coarsening, a lower dislocation density and a slight decrease in alloy strength. With optimised parameters and suitable follow-up treatment, EBM TC4 reaches properties comparable to conventional cast and forged TC4 while saving raw material and forming complex shapes quickly and efficiently, which is why the process is progressively replacing subtractive manufacturing in aerospace, chemical and medical production.
Frequently Asked Questions
Q: What grade does TC4 correspond to?
TC4 is the Chinese designation for the alpha+beta alloy Ti-6Al-4V, equivalent to Grade 5 in the ASTM system.
Q: What is additive manufacturing?
Additive manufacturing, or 3D printing, builds a solid part by slicing a three-dimensional model into thin layers and stacking the processed slices until a dense part is formed.
Q: Why is EBM preferred for TC4 among the additive processes?
Because the electron beam is not reflected, the vacuum prevents contamination, build efficiency is higher, and residual stress is low enough that a subsequent heat treatment is not required.
Q: What kind of microstructure does EBM TC4 have?
Columnar crystals grow along the building direction in the macrostructure, while the microstructure is an alpha plus beta lamellar structure that becomes finer as the cooling rate increases.
Q: What does a hot isostatic pressing treatment do?
It removes porosity and homogenises the microstructure, which markedly improves fatigue properties, although grain coarsening and a lower dislocation density slightly reduce strength.
Q: Can additive TC4 match wrought material?
With optimised forming parameters and suitable follow-up treatment, EBM TC4 reaches properties comparable to conventional cast and forged TC4 while using less raw material.
