Titanium alloys are highly significant in modern engineering due to their exceptional blend of properties such as strength, low density, and corrosion resistance. Among these alloys, titanium alloy 6-4, also known as grade 5 titanium alloy, Ti-6Al-4V, or 6Al-4V titanium, stands out as one of the most versatile titanium alloys. Additionally, titanium alloy 6-4 is the most commonly used titanium alloy and accounts for nearly half of all titanium used in the world. From use in automotive parts like exhausts and springs to medical components like joint implants, 6Al-4V titanium is used in a broad range of applications across many different industries.
1.What Is Titanium Alloy 6-4?
Titanium alloy 6-4, or grade 5 titanium, with its unique set of properties, is a remarkable alloy that is deemed the workhorse alloy of the titanium industry. Titanium 6-4, also known as Ti-6Al-4V alloy, is an alpha-beta titanium alloy in which aluminum acts as the alpha stabilizer and vanadium acts as the beta stabilizer. Ti-6Al-4V composition is 5.5–6.75% aluminum and 3.5–4.5% vanadium, with the remaining percentage being titanium. Titanium alloy 6-4 offers a great blend of high strength and stiffness, corrosion resistance, and low density. This makes it great for applications in which these properties are required such as: in the aerospace, automotive, or medical industries. Its use in these industries, as well as others, has led to a host of new products that are lighter, more efficient, and safer.
2.Who Is the Inventor of Titanium Alloy 6-4?
Titanium alloy 6-4 was invented by metallurgist and MIT professor Stan Abkowitz in 1951 at the Watertown Arsenal Laboratory, a facility of the US Army. It was invented by adding molten aluminum and vanadium to molten, pure titanium. The alloy's first widespread use was for the production of the US military's U2 high-altitude reconnaissance plane in the 1950s. The invention of the alloy and its use in the production of this aircraft catalyzed the titanium industry. Today, Ti-6Al-4V is the most commonly used titanium alloy in the world.
3.How Is Ti-6AL-4V Made?
The production of Ti-6Al-4V starts with the Kroll Process. The Kroll process is the most commonly used method to produce commercially pure titanium. In this process, titanium-rich ores such as ilmenite or rutile are heated to produce liquid titanium tetrachloride (TiCl4). Through a fractional distillation process similar to producing gasoline from crude oil, the TiCl4 liquid is purified. Afterward, magnesium is added to the liquid to produce a sponge-like titanium material and a magnesium-based salt. Next, the sponge is compressed and melted. At this stage, the appropriate ratio of aluminum and vanadium is added to the molten titanium. Once added, the Ti-6Al-4V alloy is cast into ingots and other shapes.
4.What Are the Properties of Titanium Alloy 6-4?
Titanium alloy 6-4 has many desirable properties that make it great for use in various applications. The different properties of titanium alloy 6-4 are listed below:
Low Thermal Conductivity
Titanium 6-4 has a low thermal conductivity of 6.7 W/mK. Its low thermal conductivity means the titanium alloy can be used in a broad temperature range without its mechanical properties being affected. This makes the alloy great for high-heat applications such as jet engines and landing gear in aircraft, exhaust systems in automobiles, and chemical processing equipment.
Shear Mechanism
6Al-4V Ti has low shear strength between 550–760 MPa compared to other commonly used metals like steel or aluminum. It is unsuitable for applications in which high shear forces are likely to be applied.
High Tensile Strength
Titanium 6-4 has an exceptional tensile strength of 1,170 MPa. Its high tensile strength, coupled with its low density of 4.43 g/cm3 makes it an excellent material for applications in which high strength but light weight are desired-particularly in the automotive, aerospace, and medical industries. For more information, see our guide on Material Tensile Strength.
High Modulus of Elasticity
Ti-6Al-4V has a high elastic modulus of 114 GPa. Its high modulus of elasticity means the material is stiff, rigid, and resistant to deformation. Consequently, the stiffness of 6Al-4V titanium alloy helps to minimize the deformation or bending of critical parts and acts as a vibration damper to reduce the risk of fatigue failure.
