Several systems of titanium standards are available for defining titanium alloys, their designations, chemical compositions, and mechanical properties. Understanding these titanium standards is key to selecting, comparing, and qualifying the right material for a given application.
As with other metals, the most important titanium standards include the US ASTM and SAE (specifically the aerospace AMS specifications), the European Euronorm, the German DIN, the Japanese JIS, the international ISO, and the Chinese GB and Russian GOST systems.
Titanium is capable of achieving remarkable changes in microstructure through variations in thermomechanical processing. As a result, a broad range of properties and applications can be served with a relatively small number of titanium grades. In practice, there are about 50 main titanium grades that are designated and currently in use, although only a couple of dozen are readily available commercially.
The US ASTM titanium standards recognize about 40 main titanium grades, of which grades 1 through 4 are commercially pure (unalloyed). The grades covered by ASTM, along with other alloys, are also produced to meet aerospace and military specifications (SAE-AMS and MIL-T), as well as ISO titanium standards, Euronorm, GOST, and the Japanese JIS titanium standards. Although these standards overlap in many areas, they are not interchangeable. In its efforts to achieve a more global approach to titanium standards, the Japanese Titanium Society has proposed unified systems of specifications.
The major challenge with titanium standards is not a shortage of standards defined by standards development organizations (SDOs). Instead, it is the volume of detailed, individual specifications created by aerospace companies, which tend to limit production runs. Each aerospace company maintains its own specification, including defined processing routes, so a process route permitted by one company may not be allowed by another.
This situation leads to small-batch production. Overproduced material can be stored, but it can only be used by a company that agrees to the specification. In addition, such material is often over-qualified for general industrial use because it has already passed the aerospace industry's highly detailed quality assurance requirements. For the same reason, the high proportion of material that ends up as scrap must be carefully separated to maintain the detailed pedigree that aerospace companies require.
This article covers the global standards that govern titanium alloy designation and grade coverage. The other guides in the Titanium series address what those standards define. Titanium Specifications explains the individual specification systems in detail, a closely linked topic worth reading alongside this one. Titanium Grades organises commercially pure titanium and its alloys into families, while Titanium Properties covers the strength, low density, and corrosion resistance that distinguish one grade from another. Together, they connect the standards framework with the specifications, grades, and properties it underpins.
Although roughly 50 main titanium grades are designated and in use worldwide, only about two dozen are readily available on the commercial market. ASTM alone recognizes about 40 main grades.
Because each aerospace company works to its own specification and approved processing routes, material is often produced in small, dedicated batches. A route accepted by one company may be rejected by another, which limits how widely a given batch can be used.
Overproduced material can be stored, but it can only be used by a company that accepts the specification it was made to. Because it has already passed the aerospace industry's rigorous quality assurance, it is often over-qualified, and therefore more costly than necessary, for general industrial use.
A high proportion of titanium ends up as scrap during aerospace production. This scrap must be carefully separated and tracked so that the detailed material pedigree required by aerospace companies is preserved.
Under the ASTM titanium standards, grades 1 through 4 are commercially pure (unalloyed). They vary in strength and purity and are chosen largely for their corrosion resistance.