The application of titanium alloy in mufflers

Titanium alloy, with its excellent lightweight, corrosion resistance and formability, as well as its high-end feel and creativity, is used in mufflers. In the automotive field, since the mufflers are hidden in invisible places and it is impossible to emphasize their high-end feel and creativity, the exhaust temperature is even higher than that of motorcycles. Under the issues of high-temperature oxidation resistance and high-temperature strength, titanium alloys are limited to special mufflers. In response to similar situations, some enterprises have developed Ti-1.5Al to improve high-temperature oxidation resistance and high-temperature strength in order to avoid significant damage to the formability of titanium alloys. Titanium metal was developed for reasons such as engine and catalyst conversion to increase the exhaust temperature from the front height to 700-750 ℃, and thus is adopted in the mufflers of automobiles. While being registered in the ASTM specification in 2009, it also obtained the concessions in the United States, the United Kingdom, Germany, Italy and France.

For automobiles, there is a relatively low temperature in the part after the central pipe. However, depending on the vehicle model, even the exhaust temperature in this part can reach 700 to 800 degrees Celsius. When titanium metal is exposed to such high temperatures for a long time, due to the diffusion and invasion of oxygen, the surface edge part will become fragile because a hardened layer is formed. At the same time, a stripping oxidation ratio is generated, and the titanium part of the metal undergoes a reaction, which will reduce its strength. Furthermore, fatigue strength reduction and embrittlement occur based on the coarsening of crystalline grains. In a high-temperature environment similar to this, Ti-1.5Al also has areas where its oxidation resistance cannot be matched. Therefore, if a titanium material that retains more than Ti-1.5Al in high-temperature oxidation resistance and maintains the strength characteristics of Ti-1.5Al in the forming processing of the combined parts of the muffler system can be developed, it will be the best muffler material.

Ti-0.5A1-0.45Si-0.2Nb titanium alloy is considered promising. Compared with the existing muffler materials, two types of pure titanium in JIS and Ti-1.5Al, this titanium alloy has better high-temperature oxidation resistance. These existing materials cannot be used due to problems such as embrittlement, and the possibility of using them in high-temperature environments is being considered. Meanwhile, the high-temperature strength is close to that of Ti-1.5Al. Compared with the two types of pure titanium in JIS, at 400℃, the yield strength is 3 to 4 times that of pure titanium, and the tensile strength is 2 to 3 times that of pure titanium. Therefore, this kind of titanium alloy has the same characteristic of suitable high-temperature strength as Ti-1.5Al. Furthermore, it can be expected that this alloy has the same level of formability as the two types of pure titanium in JIS.