Materials: Titanium

Titanium alloys

Actually, titanium alloys used for exhaust system fabrication are all α alloys, which use as addition small quantities of different alloying elements, as aluminum, copper, niobium, silicon and iron. Addition of these elements has increased significantly the oxidation resistance and mechanical properties, if compared whit the performance of commercially pure titanium, especially Grade 2. For production of exhaust system dedicated to high performance bikes and cars, Akrapovič buys several types of titanium alloys, from different producers worldwide; the most common purchased raw material is in shape of coils, with a thickness between 0,5 - 1,5 mm. These advanced alloys show excellent properties for their target application (high strength, elevated thermal properties, weldability); however, their use for realizing parts with complicated shapes is still limited, because of problems associated with poor formability and consequently high manufacturing costs. Formability problems of cold rolled titanium alloys are well known since several years ago, and basically are strictly related to the anisotropic behavior of the materials.

For sure, texture in titanium alloys has a big impact on the final mechanical characteristic of the product, especially formability, because, as previously explained, the slip planes of HCP lattice are not symmetrically sorted.

Akrapovič d.d. purchases for its exhaust system production six diffent types of titanium alloys from three different suppliers; four of them are mostly used for deep drawed parts, as endcap or rosette. Executing a practical deep drawing test under the press, the behavior of these materials is completely different.